Easy and Rapid Application for Residual Chlorine Analysis in Water Samples Marita Jokinen and Annu Suoniemi-Kähärä * Thermo Fisher Scientific, Vantaa, Finland *author, [email protected]

Reagent Preparation for Gallery Analyzer The Gallery analyzer TRC low and high concentration applications were compared to Introduction Materials and Methods the similar manual spectrophotometric analysis applications and the results are shown Conclusion Reagents RC R1, RC R2, and RC R3 were inserted into the analyzer approximately 30 Chlorine is commonly used for disinfection in a wide range of applications. For below in Figures 4 and 5. This study shows that TRC can be measured using the discrete analyzer, and the Method Principle minutes before the required analysis to ensure adequate stabilization of the reagents. sanitizing the water in swimming pools, chlorine is added in the form of sodium or Gallery method correlates very well with the EPA 330.5 and SFS-EN ISO 7393-2:2000 Reagents in the analyzer vials were replaced each day. Reagents RC R1 and RC R2 potassium hypochlorite or chlorine gas. Free residual chlorine (FRC) reacts instantly with the N,N-diphenyl-p-phenylene diamine FIGURES 4-5. Method correlation of Gallery analyzer vs. manual DPD-photometric manual methods. Quality control sample recoveries varied from 92 to 106%. The water were refrigerated, and the reagent RC R2 was protected from light. Reagent RC R2 (DPD) indicator to produce a red color in a pH range of 6.2 to 6.5. Absorbance is methods using TRC Low and TRC High applications. samples tested originated from several swimming pools and their concentrations were Immediately after its addition to water, a part of the chlorine reacts with manganese, showed no visible sign of aging (a pink color) during the two weeks of storage. Reagent measured at a wavelength of 510 nm. between 0.11 to 2.89 mg/L, including the spiked samples. Gallery applications are sulfides, or other organic compounds and is unavailable for disinfection. This part is RC R3 was prepared daily. In the total residual chlorine (TRC) method, chlorine liberates iodine from potassium Method Correlation: TRC Low Method Correlation: TRC High designed for concentration areas of 0.1 to 0.5 mg/L (low range) and 0.5 to 3.0 mg/L

called the “chlorine demand of water” as shown in Figure 1. iodide when an excess amount of iodine is present. The liberated iodine reacts with DPD Preliminary tests using frozen reagents showed identical results when compared to 0.7 3.5 (high range). The portion remaining is called “active chlorine” or “total active chlorine.” Part of this refrigerated reagents. 0.6 3.0 to produce a red-colored solution. Absorbance is measured at a wavelength of 510 nm. The FRC method also correlates well with SFS-EN ISO 7393-2:2000 manual methods. total chlorine can react with certain nitrogenous compounds, mostly from sweat and 0.5 , mg/L 2.5 0.02 M KMnO4 Calibrator Stock Solution Tested samples varied in concentration from 0.12 to 2.94 mg/L, including the spiked urine, forming ammonium chlorides. This group of compounds is called “combined Oxidizing agents interfere with the method and these are usually present in very low 0.4 2.0 samples. However the unstable nature of FRC offers a challenge which was concentrations compared to the residual chlorine concentrations. However, sunlight, 0.3 1.5 chlorine” and it is not as effective a disinfectant as the “free chlorine” fraction, which The 0.02 M potassium permanganate (KMnO4) calibrator stock solution is 3547 mg/L as y = 1.034x – 0.014 Results demonstrated in the low concentration area. From the QC sample of 0.1 mg/L, an consists of hypochlorite ions, hypochlorous acid, and chlorine gas. exposure to air, and agitation of the sample may critically effect the outcome. Therefore, equivalent to Chlorine. The solution was prepared from a commercial concentrate. 0.2 r² = 0.986 1.0 y = 1.049x - 0.034 r² = 0.997 82% recovery was also shown with the reference method. Other QC samples showed a quick analysis of the free residual chlorine is essential. Turbidity and color may also 0.1 0.5 Gallery Gallery Results, mg/L A KMnO4 solution is often used in calibrating the residual chlorine method because it is Gallery good recoveries ranging from 92% to 98%. interfere with colorimetric analysis and this can be avoided by application design. A high 0.0 0.0 FIGURE 1. Chemical reactions in water chlorination. concentration of monochloramine can interfere with free chlorine determination. With more stable than an active chlorine solution. The permanganate ion oxidizes the DPD 0.0 0.2 0.4 0.6 0.0 1.0 2.0 3.0 Reference Method, mg/L these samples; the application can be redesigned to avoid this by stopping the reaction molecule in the same way as any active chlorine compound. Reference Method, mg/L References with arsenite or thioacetamide. This solution is stable for up to 12 months if tightly sealed and refrigerated in an amber 1. US EPA, Methods for Chemical Analysis of Water and Wastes, Method 330.5 Equipment bottle in the dark. KMnO4 is light sensitive and degrades over time (especially at low According to these method comparison studies, all TRC methods correlated well with each concentrations). other with no significant systematic error as shown in Figures 4 and 5. The average bias in Chlorine, Total Residual (Spectrophotometric, DPD), 1978: 330 5-1. A Thermo Scientific Gallery, Gallery Plus, or Aquakem™ analyzer can be used. The this evaluation was 2.1 % for the lower concentration area (0.1 to 0.5 mg/L) and 4.9 % for 2. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; method in this paper was performed with the Gallery analyzer measured at a wavelength The calibration may be performed by separate calibrators when the dilution is done the higher concentration area (0.5 to 3.0 mg/L). Baird, R.B.; Eaton, A.D., Eds. 4500-CL (A) Introduction, American Public Health of 510 nm. manually, or by serial calibration when the dilution series is done automatically by the Gallery or Aquakem analyzer. Analysis of low concentration FRC methods in this study was fairly good as shown in Association, 22nd Edition, 2012. Gallery Application Figures 2 and 3. The average bias was -5.4 % for the low range and 0.5 % for the high 3. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; Working KMnO4-solutions Gallery applications are based on EPA 330.5 for the TRC measurement. This method is range. However, some of the individual results deviated significantly, as much as -26 % Baird, R.B.; Eaton, A.D., Eds. 4500-CL (F) DPD Ferrous Titrimetric Method, similar to SFS-EN ISO 7393-2:2000 for both TRC and FRC. Differences in the official A 12 mg/L equivalent Chlorine standard was prepared for High Range calibration from the reference results. This may be due to the nature of the analyte or delays in the American Public Health Association, 22nd Edition, 2012. methods and the Gallery applications are shown in Table 1. (0.5 to 3 mg/L) and a 1.5 mg/L equivalent Chlorine standard for Low Range analysis of samples. Therefore, inserting the FRC samples one at a time or using the (0.1 to 0.5 mg/L) calibration. STAT-Protocol is recommended. 4. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; Baird, R.B.; Eaton, A.D., Eds. 4500-CL (G) DPD Colorimetric Method, American Table 1. Comparison of residual chlorine methods. Sample Analysis and Sample types During the analysis of free residual chlorine, it was noticed that the highest evaporation (%) Public Health Association, 22nd Edition, 2012. was detected from low concentration samples. Therefore, for future analysis, analyte Samples were taken from several public swimming pools. Sample concentrations were SFS-EN ISO Gallery Chlorine Ref evaporation from the samples should be minimized by using 10 mL test tubes which are 5. Wendelken, S.C.; Losh, D.E.; Fair, P.S. Method 334.0: Determination of Residual EPA 330.5 from 0.12 to 0.58 mg/L for FRC and 0.11 to 0.89 mg/L for TRC. To cover the whole 7393-2:2000 Application (TFS R&D) filled to 1/3 of their full volume. Chlorine in Drinking Water using an On-line Chlorine Analyzer, Version 1.0; concentration range of the calibration (0.1 to 3.0 mg/L), spike samples were prepared. Office of Ground Water and Drinking Water, US EPA: Cincinnati, OH, 2009. Poster Note 71657 potassium potassium iodate + potassium potassium Calibrator Small volumes of potassium hypochlorite solution were added to a series of pool water . permanganate KI permanganate permanganate samples and the concentrations of the spiked samples were analyzed in the method 6. Leasca, S. Peeing in the Pool: So Wrong—and Bad for our Health, Study Says, comparison study. Spiked sample concentrations included 0.12 to 2.94 mg/L for FRC Quality Control Samples March 11, 2014, LA Times, http://www.latimes.com/nation/la/sh/pee-in-the-pool- Easy and Rapid Application for Residual KI in calibrator, FRC: No KI, no No KI, no no KI, no 20140311-story.html [Online] (Accessed May 5, 2015). Calibration incubation 2 min, incubation incubation, same and 0.11 to 2.89 mg/L for TRC. Each application had low and high quality control (QC) samples. QC samples were incubation, method same calibration for TRC: KI, 1 min calibration for FRC measured by both the Gallery analyzer Residual Chlorine applications and the manual 7. Krans, B. Why peeing in the pool is chemical warfare, March 31, 2104, Healthline calibration for TRC Quality control samples for this study were prepared from sodium hypochlorite solution Chlorine Analysis in Water Samples FRC and TRC (37°C) incubation and TRC spectrophotometric reference method (Chlorine Ref). Results are shown in Table 2. News, http://www.healthline.com/health-news/peeing-in-the-pool-is-chemical- (free chlorine), which was verified the same day by sodium thiosulphate titration. warfare-033114.html [Online] (Accessed May 5, 2015). The intended purpose of chlorination is to kill the microorganisms and bacteria that are Wavelength 515 nm 510 nm 510 nm 510 nm Reference Method Used for the Study harmful to people. However, it may also create some undesired byproducts, such as Table 2. QC sample results with Gallery applications and Chlorine Ref 2. 8. Chloramines- Combined Chlorine Problems, 2011, Pool Wizard, Evaluation of the Residual Chlorine methods was done in the Thermo Fisher Scientific carcinogenic trichloromethane (chloroform), mono-, di- and tri-chloroacetic acids, or KI (%) in reaction http://www.poolwizard.net/problems/chloramines.htm [Online] Marita Jokinen and Annu Suoniemi-Kähärä * 1.00 % 1.00 % 0.83 % 0.83 % Finland R&D laboratory using the Gallery discrete analyzer. In this evaluation, a series of Easy and Rapid Application for Residualtrichloramines, and highly Chlorine toxic cyanogen chloride which Analysis are formed when chlorine in is Watermixture Samples Gallery Applications Chlorine Ref (Accessed May 5, 2015). Thermo Fisher Scientifi c, Vantaa, Finland samples were measured against a manual DPD-spectrophotometric method (Chlorine Easy and Rapid Application for Residualcombined with uric acid. Chlorine Analysis in Water Samples Bias Ref) based on EPA 330.5 TRC measurement. The major difference is the EPA method Result, *author, annu.suoniemi-kähärä@thermofi sher.com Sample\ Analyte Recovery Bias Result Recovery Bias (Methods) Marita Jokinen and Annu Suoniemi-Kähärä * does not measure free chlorine. This manual reference method is similar to SFS-EN ISO Avg. % Combined chlorine in the water of swimming pools is often a symptom of an inadequate In the Gallery TRC applications (TRC Low (0.1 to 0.5 mg/L) and TRC High (0.5 to % mg/L mg/L % mg/L 7393-2:2000 which determines both total and free residual chlorine. A Thermo Scientific mg/L Marita Jokinen and Annu Suoniemi-Kähäräamount * of free chlorine. This may cause unwanted effects, such as skin irritation, 3 mg/L)), 6 µL of the phosphate buffer (RC R1) and 6 µl of the DPD indicator reagent Multiskan™ GO Spectrophotometer was used for the manual measurements at a Thermo Fisher Scientific, Vantaa, Finland breathing difficulties, and a strong odor. Therefore, it is preferred that the amount of (RC R2) were automatically added to a disposable cuvette. This was followed by an wavelength of 510 nm. QC 0.1 mg/l FRC Low 0.08 82 % -0.02 0.08 82 % -0.02 1 % Thermo Fisher Scientific, Vantaa, Finland combined chlorine is as low as possible. automatic addition of 120 µL of sample and potassium iodide solution (RC R3). In the QC 0.5 mg/l FRC Low 0.46 92 % -0.04 0.51 102 % 0.01 -9 % *author, [email protected] TRC Low application, the sample was introduced first and RC R3 next. In the TRC High *author, [email protected] achieve sufficient disinfection and to minimize any undesired byproducts, it is application, this was done in the reverse order. An incubation for 60 seconds at 37°C QC 0.1 mg/l TRC Low 0.09 92 % -0.01 0.09 90 % -0.01 1 % essential to monitor both free and combined residual chlorine concentrations in the water. occurred after the last reaction component was added. Due to the higher temperature Results and Discussion utilized, the incubation time is shorter compared to the standard methods. Finally, QC 0.5 mg/l TRC Low 0.48 97 % -0.02 0.49 99 % -0.01 -2 % Method Comparison Studies absorbance of the reaction mixture was measured at 510 nm. QC 0.5 mg/l FRC High 0.46 93 % -0.04 0.51 102 % 0.01 -9 % Rapid Analysis Using the Gallery Analyzer STAT-Protocol The Gallery analyzer TRC low and high concentration applications were compared to Reagent Preparation for Gallery Analyzer The Gallery analyzer FRC low and high concentration applications were compared to Introduction Materials and Methods QCConclusion 1.0 mg/l FRC High 0.97 97 % -0.03 1.01 101 % 0.01 -5 % The unstable nature of residual chlorine in water samples requires a rapid analysis FRCReagent applications Preparation (FRC Lowfor Gallery an FRC Analyzer High) are similar to TRC applications, but without Thethe Gallerysimilar manualanalyzer spectrophotometric TRC low and high concentrationanalysis applications applications and the were results compared are shown to Reagents RC R1, RC R2, and RC R3 were inserted into the analyzer approximately 30 the similar manual spectrophotometric analysis applications and the results are shown EasyIntroductionChlorine is commonly and used Rapidfor disinfection in aApplication wide range of applications. For for Residualmethod.MaterialsMethod Thermo Principle Scientific™ and Chlorine Methods Gallery™ discrete analyzer Analysis offers a STAT-Protocol in that Waterthe addition Samples of potassium iodide and the incubation step. thebelow similar in Figures manual 4 spectrophotometric and 5. analysis applications and the results are shown ConclusionQCThis 2.5 mg/lstudy FRCshows High that 2.46TRC can98 be % measured -0.04 using2.68 the discrete107 % analyzer,0.18 and the-8 % Reagentsminutes beforeRC R1, the RC required R2, and analysis RC R3 wereto ensure inserted adequate into the stabilization analyzer approximately of the reagents. 30 below in Figures 2 and 3. Chlorinesanitizing is thecommonly water in used swimming for disinfection pools, chlorine in a wide is added range inof theapplications. form of sodium For or minimizes the exposure of samples to the atmosphere. In many water laboratories below in Figures 4 and 5. ThisGallery study method shows correlates that TRC canvery be well measured with the EPAusing 330.5 the discrete and SFS analyzer,-EN ISO and 7393 the-2:2000 MethodFree residual Principle chlorine (FRC) reacts instantly with the N,N-diphenyl-p-phenylene diamine CombinedminutesReagents before residual in the the analyzerchlorine required (CRC)vials analysis were applications toreplaced ensure (CRC eachadequate day.Low Reagentsstabilizationand CRC High)RC of R1 the are and reagents. RC R2 QC 1.0 mg/l TRC High 0.98 98 % -0.02 1.05 105 % 0.05 -6 % sanitizingpotassium the hypochlorite water in swimming or chlorine pools, gas. chlorine is added in the form of sodium or the discrete analyzer runs non-stop, performing multiple analyses for various types of FIGURES 4-5. Method correlation of Gallery analyzer vs. manual DPD-photometric Gallerymanual method methods. correlates Quality verycontrol well sample with the recoveries EPA 330.5 varied and SFSfrom- EN92 toISO 106%. 7393 The-2:2000 water (DPD) indicator to produce a red color in a pH range of 6.2 to 6.5. Absorbance is applicationsReagentswere refrigerated, in that the subtract analyzer and the vials reagentFRC were results RCreplaced R2from was eachthe protected TRC day. results. Reagents from These light. RC Reagent calculationsR1 and RC R2 FIGURES 2-3. Method correlation of Gallery analyzer vs. manual DPD-photometric Maritapotassium hypochlorite Jokinen or chlorine andgas. Annu Suoniemi-KähäräwaterFree * residual samples chlorine simultaneously. (FRC) reacts When instantly analyzing with residual the N,N chlorine,-diphenyl it- pis- phenylenerecommended diamine FIGURESmethods 4 using-5. Method TRC Lowcorrelation and TRC of HighGallery applications. analyzer vs. manual DPD-photometric manualQCsamples 2.5 mg/l methods. testedTRC High originated Quality 2.65 control from106 severalsample % swimmingrecoveries0.15 pools 2.70varied and from108 their %92 concentrationsto 106%.0.20 The- 2water were% Immediately after its addition to water, a part of the chlorine reacts with manganese, measured at a wavelength of 510 nm. canwereshowed be refrigerated,automatically no visible and signperformed the of reagentaging with (a RC thepink R2Gallery color) was duringprotectedanalyzer. the fromtwo weekslight. Reagent of storage. RC ReagentR2 methods using FRC Low and FRC High applications. that(DPD) the indicator time a sampleto produce is in acontact red color with in thea pH atmosphere range of 6.2 is minimized.to 6.5. Absorbance When using is a methods using TRC Low and TRC High applications. samplesbetween tested 0.11 tooriginated 2.89 mg/L, from including several the swimming spiked samples.pools and Gallery their concentrations applications are were Immediatelysulfides, or otherafter itsorganic addition compounds to water, aand part is ofunavailable the chlorine for reacts disinfection. with manganese, This part is showedRC R3 nowas visible prepared sign daily.of aging (a pink color) during the two weeks of storage. Reagent Thermo Fisher Scientific, Vantaa, Finland GallerymeasuredIn the totaldiscrete at residual a wavelength analyzer, chlorine a offree (TRC)510 residual nm. method, chlorine chlorine analysis liberates can beiodine requested from potassium using the Contamination from other sample matrixes or reagents was not studied, therefore Method Correlation: TRC Low Method Correlation: TRC High betweendesigned 0.11 for toconcentration 2.89 mg/L, including areas of 0.1the tospiked 0.5 mg/L samples. (low range)Gallery and applications 0.5 to 3.0 are mg/L

called the “chlorine demand of water” as shown in Figure 1. sulfides, or other organic compounds and is unavailable for disinfection. This part is RC R3 was prepared daily. 3.5 Both methods showed fairlygood to good recoveries from the QC samples between STATiodide-Protocol. when an As excess a result, amount the analysis of iodine will is be present. performed The liberatedimmediately iodine after reacts inserting with DPD analyzingPreliminary chlorine tests samples using frozen using reagents the STAT showed-Protocol identical or by inserting results whensamples compared one at ato 0.7 Method Correlation: FRC Low Method Correlation: FRC High designed(high range). for concentration areas of 0.1 to 0.5 mg/L (low range) and 0.5 to 3.0 mg/L Method Correlation: TRC High In the total residual chlorine (TRC) method, chlorine liberates iodine from potassium Method Correlation: TRC Low called the “chlorine demand of water” as shown in Figure 1. 0.6 3.0 0.5 to 2.5 mg/L. Recoveries were from 92 to 98% for FRC and from 97 to 106% The portion remaining is called “active chlorine” or “total active chlorine.” Part of this timerefrigerated is recommended. reagents A. laboratory can also validate the method for mixed runs. 3.5 *author, [email protected] sampleproduce when into aan red theexcess-colored analyzer. amount solution. of iodine Absorbance is present. is measured The liberated at a wavelengthiodine reacts of with 510 DPD nm. Preliminary tests using frozen reagents showed identical results when compared to 0.6 0.7 3.0 (highThe range).FRC method also correlates well with SFS-EN ISO 7393-2:2000 manual methods. 0.5 , mg/L 2.5 for TRC. The smallest QC (0.1 mg/L) was close to the quantitation limit and showed Thetotal portion chlorine remaining can react is withcalled certain “active nitrogenous chlorine” or compounds, “total active mostly chlorine.” from Part sweat of this and refrigerated reagents. 0.6 2.53.0 A hypochlorite wash is usually done as part of the discrete analyzer’s daily routine. If this , mg/L ThistoOxidizing produce paper agentscomparesa red-colored interfere the solution.Residual with the Absorbance Chlorine method methodand is these measured used are by usually at the a wavelengthGallery present analyzer in ofvery 510 tolow nm. the 0.02 M KMnO4 Calibrator Stock Solution 0.4 0.4 TheTested FRC samples method variedalso correlates in concentration well with from SFS 0.12-EN toISO 2.94 7393 mg/L,-2:2000 including manual the methods. spiked urine, forming ammonium chlorides. This group of compounds is called “combined , mg/L 2.0 recoveries of 82% for FRC and 92% for TRC. Results for the reference method were total chlorine can react with certain nitrogenous compounds, mostly from sweat and protocol is used, re-flushing the tubing is recommended. A zero concentration sample 0.5 2.02.5 samples. However the unstable nature of FRC offers a challenge which was manualconcentrations method basedcompared on EPA to the 330.5 residual and SFSchlorine-EN ISOconcentrations. 7393-2:2000. However, sunlight, 0.02 M KMnO4 Calibrator Stock Solution 0.3 1.5 82%Tested and samples 90%, respectively. varied in concentration Low recoveries from are 0.12 thought to 2.94 to mg/L, be the including result of the evaporation spiked chlorine” and it is not as effective a disinfectant as the “free chlorine” fraction, which Oxidizing agents interfere with the method and these are usually present in very low The 0.02 M potassium permanganate (KMnO4) calibrator stock solution is 3547 mg/L as 0.4 y = 1.034x – 0.014 1.5Results 2.0 PO71657-EN 06/15S urine, forming ammonium chlorides. This group of compounds is called “combined y = 0.946x – 0.009 exposure to air, and agitation of the sample may critically effect the outcome. Therefore, can also be measured before sample analysis to ensure that all residual analyte is fully 0.2 0.2 r² = 0.986 y y= = 1. 1.049x 005x – - 0.0250.034 samples.demonstrated However in the the low unstable concentration nature of area. FRC From offers the a challengeQC sample which of 0.1 was mg/L, an consists of hypochlorite ions, hypochlorous acid, and chlorine gas. concentrations compared to the residual chlorine concentrations. However, sunlight, equivalent to Chlorine. The solution was prepared from a commercial concentrate. 0.3 r² = 0.992 1.01.5 1.0 r² = 0.998 of the analyte. chlorine” and it is not as effective a disinfectant as the “free chlorine” fraction, which removedThe 0.02 from M potassium the instrument. permanganate (KMnO4) calibrator stock solution is 3547 mg/L as y = 1.034x – 0.014 Results r² = 0.997 82% recovery was also shown with the reference method. Other QC samples showed a quick analysis of the free residual chlorine is essential. Turbidity and color may also Reagent Preparation for Gallery Analyzer The 0.2Gallery0.1 analyzer TRC low andr² =high 0.986 concentration0.5 0.5 applications were comparedy = 1.049x - to0.034 demonstrated in the low concentration area. From the QC sample of 0.1 mg/L, an exposure to air, and agitation of the sample may critically effect the outcome. Therefore, 0.0 Gallery Results, mg/L 1.0 All trademarks are the property of Thermo Fisher Scientific and its subsidiaries. consists of hypochlorite ions, hypochlorous acid, and chlorine gas. equivalent to Chlorine. The solution was prepared from a commercial concentrate. Gallery In general, Gallery analyzer applications showed lower results than the reference Introduction Materials interfere with colorimetric and analysisMethods and this can be avoided by application design. A high A KMnO4 solution is often used in calibrating the residual chlorine method because it is the similar0.0 manual spectrophotometric analysis applications0.0 and the results arer² =shown 0.997 Conclusion82%good recovery recoveries was ranging also shown from with92% the to 98reference%. method. Other QC samples showed

Gallery Results, mg/L 0.00.1 0.2 0.4 0.6 0.0 a quick analysis of the free residual chlorine is essential. Turbidity and color may also Results Gallery 0.5 Reagents RC R1, RC R2, and RC R3 were inserted into the analyzer approximately 30 Gallery Results, mg/L 0.0 0.2 0.4 0.6 0.0 1.0 2.0 3.0 method, Chlorine Ref. This information is not intended to encourage use of these products in any manners that might infringe the FIGURE 1. Chemical reactions in water chlorination. more stable than an active chlorine solution. The permanganate ion oxidizes the DPD Gallery Chlorine is commonly used for disinfection in a wide range of applications. For interfereconcentration with colorimetric of monochloramine analysis and can this interfere can be with avoided free chlorine by application determination. design. WithA high A KMnO4 solution is often used in calibrating the residual chlorine method because it is below0.0 in FiguresReference 4 and Method, 5. mg/L 0.0 1.0 2.0 3.0 Thisgood study recoveries shows rangingthat TRC from can 92% be measured to 98%. using the discrete analyzer, and the Method Principle minutesmolecule before in the the same required way analysisas any active to ensure chlorine adequate compound. stabilization of the reagents. Reference Method, mg/L 0.0 Reference Method, mg/L intellectual property rights of others. sanitizingFIGURE 1.the Chemical water in swimming reactions pools, in water chlorine chlorination. is added in the form of sodium or concentrationthese samples; of monochloraminethe application can can be interfere redesigned with tofree avoid chlorine this by determination. stopping the Withreaction more stable than an active chlorine solution. The permanganate ion oxidizes the DPD 0.0 0.2 0.4 0.6 0.0 Reference1.0 Method,2.0 mg/L3.0 Gallery method correlates very well with the EPA 330.5 and SFS-EN ISO 7393-2:2000 Free residual chlorine (FRC) reacts instantly with the N,N-diphenyl-p-phenylene diamine Reagents in the analyzer vials were replaced each day. Reagents RC R1 and RC R2 Reference Method, mg/L References potassium hypochlorite or chlorine gas. thesewith arsenitesamples; or the thioacetamide application can. be redesigned to avoid this by stopping the reaction moleculeThis solution in the is same stable way for asup anyto 12 active months chlorine if tightly compound. sealed and refrigerated in an amber FIGURES 4-5. Method correlation of Gallery analyzer vs. manualReference DPD Method,-photometric mg/L manual methods. Quality control sample recoveries varied from 92 to 106%. The water (DPD) indicator to produce a red color in a pH range of 6.2 to 6.5. Absorbance is were refrigerated, and the reagent RC R2 was protected from light. Reagent RC R2 References with arsenite or thioacetamide. 4 methods using TRC Low and TRC High applications. samples1. US tested EPA, originated Methods fromfor Chemical several swimming Analysis of pools Water and and their Wastes concentrations, Method 330.5 were Immediately after its addition to water, a part of the chlorine reacts with manganese, Equipment showedThisbottle solution inno the visible isdark. stable sign KMnO forof agingup is to light 12(a pinksensitivemonths color) if and tightly during degrades sealed the two andover weeks refrigerated time of (especially storage. in an Reagent at amber low According to these method comparison studies, all TRC methods correlated well with each measured at a wavelength of 510 nm. between1. USChlorine, 0.11 EPA, to Methods2.89 Total mg/L, Residual for including Chemical (Spectrophotometric the Analysis spiked ofsamples. Water, DPD), and Gallery 1978Wastes applications: 330, Method 5-1. 330.5are sulfides, or other organic compounds and is unavailable for disinfection. This part is RCbottleconcentrations R3 inwas the prepared dark.). KMnO daily.4 is light sensitive and degrades over time (especially at low Accordingother with to no these significant method systematic comparison error studies, as shown all TRC in Figures methods 4 and correlated 5. The averagewell with biaseach in EquipmenA Thermot Scientific Gallery, Gallery Plus, or Aquakem™ analyzer can be used. The designed for concentration areas of 0.1 to 0.5 mg/L (low range) and 0.5 to 3.0 mg/L In the total residual chlorine (TRC) method, chlorine liberates iodine from potassium concentrations). this evaluationMethod was Correlation: 2.1 % for theTRC lower Low concentration areaMethod (0.1 to Correlation: 0.5 mg/L) and TRC 4.9 High % for 2. Chlorine,Standard Total Methods Residual for the (Spectrophotometric Examination of Water, DPD), and 1978 Wastewater,: 330 5-1. Rice, E.W.; called the “chlorine demand of water” as shown in Figure 1. other with no significant systematic error as shown in Figures 4 and 5. The average bias in

The calibration may be performed by separate calibrators when the dilution is done Amethod Thermo in Scientific this paper Gallery, was performed Gallery Plus, with or the Aquakem Gallery ™analyzer analyzer measured can be used. at a wavelength The Preliminary tests using frozen reagents showed identical results when compared to 0.7 3.5 (high range). iodide when an excess amount of iodine is present. The liberated iodine reacts with DPD thisthe evaluation higher concentration was 2.1 % forarea the (0.5 lower to 3.0 concentration mg/L). area (0.1 to 0.5 mg/L) and 4.9 % for 2. StandardBaird, R.B.; Methods Eaton, for A.D., the Eds.Examination 4500-CL of (A) Water Introduction, and Wastewater, American Rice, Public E.W.; Health The portion remaining is called “active chlorine” or “total active chlorine.” Part of this of 510 nm. refrigeratedThemanually, calibration orreagents by may serial .be calibrationperformed whenby separate the dilution calibrators series whenis done the automatically dilution is done by the 0.6 3.0 tomethod produce in thisa red paper-colored was solution. performed Absorbance with the Gallery is measured analyzer at ameasured wavelength at aof wavelength 510 nm. the higher concentration area (0.5 to 3.0 mg/L). The FRCAssociation, method also 22nd correlates Edition, well 2012 with. SFS-EN ISO 7393-2:2000 manual methods. Gallery or Aquakem analyzer. , mg/L Baird, R.B.; Eaton, A.D., Eds. 4500-CL (A) Introduction, American Public Health total chlorine can react with certain nitrogenous compounds, mostly from sweat and of 510 nm. manually, or by serial calibration when the dilution series is done automatically by the Analysis0.5 of low concentration FRC methods in this2.5 study was fairly good as shown in Gallery Application 0.02 M KMnO4 Calibrator Stock Solution Tested samples varied in concentration from 0.12 to 2.94 mg/L, including the spiked urine, forming ammonium chlorides. This group of compounds is called “combined Oxidizing agents interfere with the method and these are usually present in very low Gallery or Aquakem analyzer. AnalysisFigures0.4 of2 andlow concentration3. The average FRC bias methods was -5.4 in % this for2.0 studythe low was range fairly and good 0.5 as % shown for the in high 3. Association,Standard Methods 22nd Edition, for the 2012 Examination. of Water and Wastewater, Rice, E.W.; Working KMnO4-solutions samples. However the unstable nature of FRC offers a challenge which was concentrationsGallery Application compared to the residual chlorine concentrations. However, sunlight, range.0.3 However, some of the individual results deviated1.5 significantly, as much as -26 % chlorine” and it is not as effective a disinfectant as the “free chlorine” fraction, which Gallery applications are based on EPA 330.5 for the TRC measurement. This method is The 0.02 M potassium permanganate (KMnO4) calibrator stock solution is 3547 mg/L as Figures 2 and 3. The averagey =bias 1.034x was – 0.014 -5.4 % forResults the low range and 0.5 % for the high 3. StandardBaird, R.B.; Methods Eaton, for A.D., the Eds.Examination 4500-CL of (F) Water DPD and Ferrous Wastewater, Titrimetric Rice, Method, E.W.; Working KMnO4-solutions demonstrated in the low concentration area. From the QC sample of 0.1 mg/L, an consists of hypochlorite ions, hypochlorous acid, and chlorine gas. exposuresimilar to to SFS air, -andEN agitationISO 7393 of-2:2000 the sample for both may TRC critically and FRC. effect Differences the outcome. in the Therefore, official equivalentA 12 mg/L to equivalent Chlorine. TheChlorine solution standard was prepared was prepared from a for commercial High Range concentrate. calibration range.from0.2 the However, reference some results. of the This individualr² =may 0.986 be results due to deviated the1.0 nature significantly, of the analyte as much ory = delays1.049x as - -0.03426 in %the American Public Health Association, 22nd Edition, 2012. Gallery applications are based on EPA 330.5 for the TRC measurement. This method is r² = 0.997 82% recoveryBaird, R.B.; was alsoEaton, shown A.D., with Eds. the 4500 reference-CL (F) method.DPD Ferrous Other Titrimetric QC samples Method, showed a quickmethods analysis and the of theGallery free applicationsresidual chlorine are shown is essential. in Table Turbidity 1. and color may also A(0.5 12 mg/Lto 3 mg/L)equivalent and a Chlorine 1.5 mg/L standard equivalent was Chlorine prepared standard for High for Range Low Rangecalibration analysis0.1 of samples. Therefore, inserting the FRC0.5 samples one at a time or using the similar to SFS-EN ISO 7393-2:2000 for both TRC and FRC. Differences in the official from Gallery Results, mg/L the reference results. This may be due to the nature of the analyte or delays in the American Public Health Association, 22nd Edition, 2012. Gallery Gallery 4. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; interfere with colorimetric analysis and this can be avoided by application design. A high A (0.1KMnO to 40.5 solution mg/L) is calibration. often used in calibrating the residual chlorine method because it is STAT0.0 -Protocol is recommended. good recoveries ranging from 92% to 98%. methods and the Gallery applications are shown in Table 1. (0.5 to 3 mg/L) and a 1.5 mg/L equivalent Chlorine standard for Low Range analysis of samples. Therefore, inserting the FRC 0.0samples one at a time or using the Baird, R.B.; Eaton, A.D., Eds. 4500-CL (G) DPD Colorimetric Method, American FIGURE 1. Chemical reactions in water chlorination. concentration of monochloramine can interfere with free chlorine determination. With more stable than an active chlorine solution. The permanganate ion oxidizes the DPD 0.0 0.2 0.4 0.6 0.0 1.0 2.0 3.0 4. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; Table 1. Comparison of residual chlorine methods. (0.1Sample to 0.5 Analysis mg/L) calibration. and Sample types STATDuring-Protocol the analysisReference is recommended. of Method, free residual mg/L chlorine, it was noticed that the highest evaporation (%) Public Health Association, 22nd Edition, . these samples; the application can be redesigned to avoid this by stopping the reaction molecule in the same way as any active chlorine compound. Reference Method, mg/L Baird, R.B.; Eaton, A.D., Eds. 4500-CL (G) 2012 DPD Colorimetric Method, American Table 1. Comparison of residual chlorine methods. Sample Analysis and Sample types Duringwas detected the analysis from oflow free concentration residual chlorine, samples. it was Therefore, noticed thatfor future the highest analysis, evaporation analyte (%) ReferencesPublic Health Association, 22nd Edition, 2012. with arsenite or thioacetamide. SFS-EN ISO Gallery Chlorine Ref ThisSamples solution were is stable taken for from up severalto 12 months public ifswimming tightly sealed pools. and Sample refrigerated concentrations in an amber were 5. Wendelken, S.C.; Losh, D.E.; Fair, P.S. Method 334.0: Determination of Residual EPA 330.5 wasevaporation detected from thelow samplesconcentration should samples. be minimized Therefore, by using for future 10 mL analysis, test tubes analyte which are 7393-2:2000 Application (TFS R&D) from 0.12 to 0.58 mg/L for FRC and 0.11 to 0.89 mg/L for TRC. To cover the whole 1. USChlorine EPA, Methods in Drinking for ChemicalWater using Analysis an On of-line Water Chlorine and Wastes Analyzer, Method, Version 330.5 1.0; Equipment SFS-EN ISO Gallery Chlorine Ref bottleSamples in the were dark. taken KMnO from4 is several light sensitive public swimming and degrades pools. over Sample time (especiallyconcentrations at low were Accordingfilled to 1/3 to theseof their method full volume. comparison studies, all TRC methods correlated well with each 5. Wendelken, S.C.; Losh, D.E.; Fair, P.S. Method 334.0: Determination of Residual EPA 330.5 concentration range of the calibration (0.1 to 3.0 mg/L), spike samples were prepared. evaporation from the samples should be minimized by using 10 mL test tubes which are Chlorine, Total Residual (Spectrophotometric, DPD), : 330 5-1. 7393-2:2000 Application (TFS R&D) concentrationsfrom 0.12 to 0.58). mg/L for FRC and 0.11 to 0.89 mg/L for TRC. To cover the whole other with no significant systematic error as shown in Figures 4 and 5. The average bias in ChlorineOffice of in Ground Drinking Water Water and using Drinking an On Water,-line Chlorine US EPA:1978 Analyzer Cincinnati,, Version OH, 2009 1.0; . potassium potassium iodate + potassium potassium filled to 1/3 of their full volume. A ThermoCalibrator Scientific Gallery, Gallery Plus, or Aquakem™ analyzer can be used. The concentrationSmall volumes range of potassium of the calibration hypochlorite (0.1 tosolution 3.0 mg/L), were spike added samples to a series were of prepared. pool water . permanganate KI permanganate permanganate this evaluation was 2.1 % for the lower concentration area (0.1 to 0.5 mg/L) and 4.9 % for 2. 6. StandardOfficeLeasca of ,GroundMethods S. Peeing Water for in the the and Examination Pool: Drinking So Wrong Water, of Water— USand andEPA: Bad Wastewater, forCincinnati, our Health, OH,Rice, Study 2009 E.W.; .Says, method in this paper waspotassium performed withpotassium the Gallery iodate + analyzer potassium measured at apotassium wavelength Thesamples calibration and themay concentrations be performed byof theseparate spiked calibrators samples were when analyzed the dilution in the is donemethod Calibrator Small volumes of potassium hypochlorite solution were added to a series of pool water the. higher concentration area (0.5 to 3.0 mg/L). Baird,March R.B.; 11, Eaton,2014, LAA.D., Times, Eds. http://www.latimes.com/nation/la/sh/pee 4500-CL (A) Introduction, American Public-in- theHealth-pool - of 510 nm. permanganate KI permanganate permanganate manually,comparison or by study. serial Spiked calibration sample when concentrations the dilution series included is done 0.12 automatically to 2.94 mg/L forby theFRC Quality Control Samples 6. Leasca, S. Peeing in the Pool: So Wrong—and Bad for our Health, Study Says, KI in calibrator, FRC: No KI, no No KI, no samples and the concentrations of the spiked samples were analyzed in the method Association, 22nd Edition, . no KI, no Gallery or Aquakem analyzer. AnalysisQuality of low concentrationControl FRC Samples methods in this study was fairly good as shown in March20140311 11, 2014,-story.html LA Times, [Online]2012 http://www.latimes.com/nation/la/sh/pee (Accessed May 5, 2015). -in-the-pool- Calibration incubation 2 min, incubation incubation, same comparisonand 0.11 to study. 2.89 mg/L Spiked for sampleTRC. concentrations included 0.12 to 2.94 mg/L for FRC Each application had low and high quality control (QC) samples. QC samples were Gallery Application incubation, KI in calibrator, FRC: No KI, no No KI, no method no KI, no same calibration for TRC: KI, 1 min calibration for FRC Figuresmeasured 2 and by 3. both The the average Gallery bias analyzer was -5.4 Residual % for the Chlorine low range applications and 0.5 and% for the the manual high 3. 7. Standard20140311Krans, B. Methods- story.htmlWhy peeing for [Online] the in Examination the (Accessedpool is chemical of MayWater 5, warfare, and2015). Wastewater, March 31, Rice, 2104, E.W.; Healthline Calibration calibration for TRC incubation 2 min, incubation incubation, same WorkingandQuality 0.11 controlKMnOto 2.894 samples-mg/Lsolutions for forTRC. this study were prepared from sodium hypochlorite solution Each application had low and high quality control (QC) samples. QC samples were incubation, FRC and TRC (37°C) incubation and TRC range.spectrophotometric However, some reference of the individual method results(Chlorine deviated Ref). Resultssignificantly, are shown as much in Table as -26 2. % Baird, R.B.; Eaton, A.D., Eds. 4500-CL (F) DPD Ferrous Titrimetric Method, Gallerymethod applications are based on EPAsame 330.5 calibration for the for TRC TRC: measurement. KI, 1 min Thiscalibration method for FRC is measured by both the Gallery analyzer Residual Chlorine applications and the manual 7. KransNews,, B. http://www.healthline.com/health Why peeing in the pool is chemical-news/peeing warfare, -Marchin-the -31,pool 2104,-is-chemical Healthline- calibration for TRC AQuality (free12 mg/L chlorine), control equivalent samples which Chlorine was for thisverified standard study the were samewas prepared prepared day by sodiumfrom for High sodium thiosulphate Range hypochlorite calibration titration. solution from the reference results. This may be due to the nature of the analyte or delays in the similar to SFS-EN ISO 7393-2:2000 for FRCboth and TRC TRC and FRC.(37°C) Differences incubation in theand official TRC spectrophotometric reference method (Chlorine Ref). Results are shown in Table 2. AmericanNews,warfare http://www.healthline.com/health- Public033114.html Health [Online] Association, (Accessed 22nd-news/peeing Edition,May 5, 2015).2012-in.- the-pool-is-chemical- Wavelength 515 nm 510 nm 510 nm 510 nm (0.5(free to chlorine), 3 mg/L) andwhich a 1.5 was mg/L verified equivalent the same Chlorine day by standard sodium thiosulphatefor Low Range titration. analysis of samples. Therefore, inserting the FRC samples one at a time or using the The intended purpose of chlorination is to kill the microorganisms and bacteria that are methods and the Gallery applications are shown in Table 1. Reference Method Used for the Study warfare-033114.html [Online] (Accessed May 5, 2015). (0.1 to 0.5 mg/L) calibration. STATTable-Protocol 2. QC sampleis recommended. results with Gallery applications and Chlorine Ref 2. 4. 8. StandardChloramines Methods- Combined for the Examination Chlorine Problems, of Water 2011, and Wastewater,Pool Wizard, Rice, E.W.; Theharmful intended to people. purpose However, of chlorination it may also is to create kill the some microorganisms undesired byproducts, and bacteria such that asare Wavelength 515 nm 510 nm 510 nm 510 nm Reference Method Used for the Study KI (%) in reaction Evaluation of the Residual Chlorine methods was done in the Thermo Fisher Scientific Baird,http://www.poolwizard.net/problems/chloramines.htm R.B.; Eaton, A.D., Eds. 4500-CL (G) DPD Colorimetric [Online] Method, American carcinogenic trichloromethane (chloroform), mono-, di- and tri-chloroacetic acids, or Table 1. Comparison of residual1.00 % chlorine1.00 methods. % 0.83 % 0.83 % Table 2. QC sample results with Gallery applications and Chlorine Ref 2. 8. Chloramines- Combined Chlorine Problems, 2011, Pool Wizard, harmful to people. However, it may also create some undesired byproducts, such as mixture SampleFinland Analysis R&D laboratory and Sample using typesthe Gallery discrete analyzer. In this evaluation, a series of During the analysis of free residual chlorine, it was noticed that the highest evaporation (%) Public(Accessed Health May Association, 5, 2015). 22nd Edition, 2012. trichloramines, and highly toxic cyanogen chloride which are formed when chlorine is KI (%) in reaction Evaluation of the Residual Chlorine methods was done in the Thermo Fisher Scientific Gallery Applications Chlorine Ref http://www.poolwizard.net/problems/chloramines.htm [Online] carcinogenic trichloromethane (chloroform), mono-, di- and tri-chloroacetic acids, or 1.00 % 1.00 % 0.83 % 0.83 % samples were measured against a manual DPD-spectrophotometric method (Chlorine was detected from low concentration samples. Therefore, for future analysis, analyte mixture SamplesFinland R&D were laboratory taken from using several the publicGallery swimming discrete analyzer.pools. Sample In this concentrations evaluation, a series were of Bias (Accessed May 5, 2015). trichloraminescombined with, and uric highly acid. toxic cyanogen chloride which are formed when chlorine is SFS-EN ISO Gallery Chlorine Ref evaporation from the samplesGallery Applications should be minimized by usingChlorine 10 Ref mL test tubes which are 5. Wendelken, S.C.; Losh, D.E.; Fair, P.S. Method 334.0: Determination of Residual EPA 330.5 samplesRef) based were on measured EPA 330.5 against TRC measurement. a manual DPD The-spectrophotometric major difference methodis the EPA (Chlorine method Sample\ Analyte Result, (Methods) combined with uric acid. 7393-2:2000 Application (TFS R&D) from 0.12 to 0.58 mg/L for FRC and 0.11 to 0.89 mg/L for TRC. To cover the whole Recovery Bias Result Recovery Bias Bias Chlorine in Drinking Water using an On-line Chlorine Analyzer, Version 1.0; does not measure free chlorine. This manual reference method is similar to SFS-EN ISO filled to 1/3 of their full volume.Avg. % Combined chlorine in the water of swimming pools is often a symptom of an inadequate In the Gallery TRC applications (TRC Low (0.1 to 0.5 mg/L) and TRC High (0.5 to concentrationRef) based on range EPA 330.5of the TRCcalibration measurement. (0.1 to 3.0 The mg/L), major spike difference samples is thewere EPA prepared. method Sample\ Analyte Result, % mg/L mg/L % mg/L (Methods) Office of Ground Water and Drinking Water, US EPA: Cincinnati, OH, 2009. 7393-2:2000 which determines both total and free residual chlorine. A Thermo Scientific mg/L Recovery Bias Result Recovery Bias 3 mg/L)), 6 µL of the potassiumphosphate bufferpotassium (RC R1) iodate and + 6 µl potassiumof the DPD indicatorpotassium reagent Smalldoes notvolumes measure of potassium free chlorine. hypochlorite This manual solution reference were added method to isa similarseries ofto poolSFS -waterEN ISO Avg. % Combinedamount of chlorine free chlorine. in the Thiswater may of swimming cause unwanted pools is effects, often a suchsymptom as skin of anirritation, inadequate In theCalibrator Gallery TRC applications (TRC Low (0.1 to 0.5 mg/L) and TRC High (0.5 to . % mg/L mg/L % mg/L (RC R2) were automaticallypermanganate added to a disposableKI cuvettepermanganate. This was followedpermanganate by an samples7393Multiskan-2:2000 and™ the whichGO concentrations Spectrophotometer determines bothof the total wasspiked and used samplesfree for residual the weremanual chlorine. analyzed measurements A inThermo the method Scientificat a mg/L 6. Leasca, S. Peeing in the Pool: So Wrong—and Bad for our Health, Study Says, amountbreathing of freedifficulties, chlorine. and This a strongmay cause odor. unwantedTherefore, effects, it is preferred such as that skin the irritation, amount of 3 mg/L)), 6 µL of the phosphate buffer (RC R1) and 6 µl of the DPD indicator reagent QC 0.1 mg/l FRC Low 0.08 82 % -0.02 0.08 82 % -0.02 1 % automatic addition of 120 µL of sample and potassium iodide solution (RC R3). In the comparisonMultiskanwavelength™ study. GO of 510 Spectrophotometer Spiked nm. sample concentrations was used for included the manual 0.12 measurements to 2.94 mg/L for at FRCa Quality Control Samples March 11, 2014, LA Times, http://www.latimes.com/nation/la/sh/pee-in-the-pool- breathingcombined difficulties, chlorine is and as lowa strong as possible. odor. Therefore, it is preferred that the amount of (RC R2) were automatically added to KIa disposablein calibrator, cuvetteFRC:. ThisNo KI, was no followedNo byKI, anno QC 0.1 mg/l FRC Low 0.08 82 % -0.02 0.08 82 % -0.02 1 % TRC Low application,no the KI, sampleno was introduced first and RC R3 next. In the TRC High wavelength of 510 nm. QC 0.5 mg/l FRC Low 0.46 92 % -0.04 0.51 102 % 0.01 -9 % 20140311-story.html [Online] (Accessed May 5, 2015). automaticCalibration addition of 120 µL of sampleincubation and potassium 2 min, iodideincubation solution (RCincubation, R3). In samethe and 0.11 to 2.89 mg/L for TRC. Each application had low and high quality control (QC) samples. QC samples were combined chlorine is as low as possible. incubation, To achieve sufficient disinfection and to minimize any undesired byproducts, it is TRCapplication, methodLow application, this was donethe sample in the reversewassame introduced calibration order. An forfirst incubation andTRC: RC KI, forR31 min 60next. seconds calibrationIn the TRCat for37 FRC°HighC measuredQCQC 0.5 0.1 mg/l mg/l by bothFRCTRC Low the Low Gallery0.460.09 analyzer9292 % % Residual -0.04-0.01 Chlorine 0.510.09 applications 10290 % % and0.01-0.01 the manual-91 % % 7. Krans, B. Why peeing in the pool is chemical warfare, March 31, 2104, Healthline calibration for TRC Quality control samples for this study were prepared from sodium hypochlorite solution application,occurred after this thewas last done reaction in the componentreverseFRC order. and was TRC An added. incubation(37 Due°C) incubation tofor the 60 higherseconds temperatureand at TRC37°C Results and Discussion spectrophotometric reference method (Chlorine Ref). Results are shown in Table 2. News, http://www.healthline.com/health-news/peeing-in-the-pool-is-chemical- Toessential achieve to sufficient monitor disinfectionboth free and and combined to minimize residual any undesired chlorine concentrations byproducts, it isin the water. (free chlorine), which was verified the same day by sodium thiosulphate titration. QCQC 0.1 0.5 mg/l mg/l TRCTRC Low Low 0.090.48 9297 % % -0.01-0.02 0.090.49 9099 % % -0.01-0.01 1- %2 % occurredutilized, afterthe incubation the last reaction time is componentshorter compared was added. to the Due standard to the methods. higher temperature Finally, Results and Discussion warfare-033114.html [Online] (Accessed May 5, 2015). essential to monitor both free and combined residual chlorine concentrations in the water. Method Comparison Studies QC 0.5 mg/l TRC Low 0.48 97 % -0.02 0.49 99 % -0.01 -2 % TheRapid intended Analysis purpose Using of chlorinationthe Gallery isAnalyzer to kill the STAT microorganisms-Protocol and bacteria that are utilized,absorbanceWavelength the incubation of the reaction time515 nm is mixture shorter was compared510 measured nm to the at 510standard 510nm. nm methods. Finally,510 nm Reference Method Used for the Study QC 0.5 mg/l FRC High 0.46 93 % -0.04 0.51 102 % 0.01 -9 % MethodThe Gallery Comparison analyzer StudiesFRC low and high concentration applications were compared to Table 2. QC sample results with Gallery applications and Chlorine Ref 2. 8. Chloramines- Combined Chlorine Problems, 2011, Pool Wizard, harmful to people. However, it may also create some undesired byproducts, such as absorbanceFRC applications of the reaction(FRC Low mixture an FRC was High) measured are similar at 510 to nm.TRC applications, but without QCQC 0.5 1.0 mg/l mg/l FRCFRC High High 0.460.97 9397 % % -0.04-0.03 0.511.01 102101 % % 0.010.01 -9- 5% % RapidThe unstable Analysis nature Using of the residual Gallery chlorine Analyzer in water STAT samples-Protocol requires a rapid analysis KI (%) in reaction Evaluationthe similar of manual the Residual spectrophotometric Chlorine methods analysis was applicationsdone in the Thermoand the Fisherresults Scientificare shown http://www.poolwizard.net/problems/chloramines.htm [Online] carcinogenic trichloromethane (chloroform), mono-, di- and tri-chloroacetic acids, or 1.00 % 1.00 % 0.83 % 0.83 % The Gallery analyzer FRC low and high concentration applications were compared to FRCthe additionapplications of potassium (FRC Low iodide an FRC and High) the incubation are similar step. to TRC applications, but without Finland R&D laboratory using the Gallery discrete analyzer. In this evaluation, a series of QCQC 1.0 2.5 mg/l mg/l FRCFRC High High 0.972.46 9798 % % -0.03-0.04 1.012.68 101107 % % 0.010.18 -5- 8% % (Accessed May 5, 2015). trichloraminesThemethod. unstable Thermo ,nature and Scientific™highly of residual toxic Gallery™cyanogen chlorine indiscrete chloride water samplesanalyzer which are requiresoffers formed a aSTAT when rapid-Protocol chlorineanalysis thatis mixture thebelow similar in Figures manual 2 spectrophotometric and 3. analysis applications and the results are shown Gallery Applications Chlorine Ref samples were measured against a manual DPD-spectrophotometric method (Chlorine minimizes the exposure of samples to the atmosphere. In many water laboratories theCombined addition residualof potassium chlorine iodide (CRC) and applicationsthe incubation (CRC step. Low and CRC High) are QC 2.5 mg/l FRC High 2.46 98 % -0.04 2.68 107 % 0.18 Bias-8 % combinedmethod. Thermo with uric Scientific™ acid. Gallery™ discrete analyzer offers a STAT-Protocol that below in Figures 2 and 3. QC 1.0 mg/l TRC High 0.98 98 % -0.02 1.05 105 % 0.05 -6 % the discrete analyzer runs non-stop, performing multiple analyses for various types of Ref) based on EPA 330.5 TRC measurement. The major difference is the EPA method Sample\ Analyte Result, (Methods) minimizes the exposure of samples to the atmosphere. In many water laboratories Combinedapplications residual that subtract chlorine the (CRC) FRC applications results from (CRC the TRC Low results. and CRC These High) calculations are FIGURES 2-3. Method correlation of Gallery analyzer vs. manual DPD-photometric Recovery Bias Result Recovery Bias does not measure free chlorine. This manual reference method is similar to SFS-EN ISO QCQC 1.0 2.5 mg/l mg/l TRCTRC High High Avg.0.982.65 98106 % % -0.020.15 1.052.70 105108 % % 0.050.20 -6- 2% % thewater discrete samples analyzer simultaneously. runs non-stop, When performing analyzing multiple residual analyses chlorine, for it is various recommended types of In canthe beGallery automatically TRC applications performed (TRC with Low the Gallery(0.1 to 0.5analyzer. mg/L) and TRC High (0.5 to % mg/L mg/L % mg/L % Combined chlorine in the water of swimming pools is often a symptom of an inadequate applications that subtract the FRC results from the TRC results. These calculations FIGURESmethods 2 using-3. Method FRC Lowcorrelation and FRC of HighGallery applications. analyzer vs. manual DPD-photometric mg/L that the time a sample is in contact with the atmosphere is minimized. When using a 3 mg/L)), 6 µL of the phosphate buffer (RC R1) and 6 µl of the DPD indicator reagent 7393-2:2000 which determines both total and free residual chlorine. A Thermo Scientific QC 2.5 mg/l TRC High 2.65 106 % 0.15 2.70 108 % 0.20 -2 % amountwater samples of free chlorine. simultaneously. This may When cause analyzing unwanted residual effects, chlorine, such as it skinis recommended irritation, can be automatically performed with the Gallery analyzer. methods using FRC Low and FRC High applications. Gallery discrete analyzer, a free residual chlorine analysis can be requested using the (RCContamination R2) were automatically from other sampleadded to matrixes a disposable or reagents cuvette was. This not was studied, followed therefore by an Multiskan™ GO Spectrophotometer was used for the manual measurements at a breathingthat the timedifficulties, a sample and is a in strong contact odor. with Therefore, the atmosphere it is preferred is minimized. that the When amount using of a QCBoth 0.1 mg/l methods FRC Lowshowed 0.08 fairlygood 82 % to good-0.02 recoveries 0.08 from the82 % QC samples-0.02 between1 % STAT-Protocol. As a result, the analysis will be performed immediately after inserting automaticContaminationanalyzing addition chlorine from of samples other120 µL sample of using sample matrixes the andSTAT potassiumor-Protocol reagents oriodide was by insertingnot solution studied, samples(RC therefore R3). one In the at a wavelengthMethod of 510 nm.Correlation: FRC Low Method Correlation: FRC High

combinedGallery discrete chlorine analyzer, is as low a asfree possible. residual chlorine analysis can be requested using the time is recommended. A laboratory can also validate the method for mixed runs. QCBoth0.5 0.5 to methodsmg/l 2.5 mg/L.FRC showed Low Recoveries 0.46fairlygood were92 to% from good 92- 0.04recoveries to 98% for0.51 from FRC the and102 QC % from samples 970.01 to 106%between-9 % STATthe sample-Protocol. into As the a result,analyzer. the analysis will be performed immediately after inserting TRCanalyzing Low application, chlorine samples the sample using wasthe STAT introduced-Protocol first or and by RCinserting R3 next. samples In the one TRC at High a 0.6 Method Correlation: FRC Low 3.0 Method Correlation: FRC High

for TRC. The smallest QC (0.1 mg/L) was close to the quantitation limit and showed application, time is recommended. this was done A laboratoryin the reverse can order.also validate An incubation the method for 60 for seconds mixed runs. at 37 ° C 2.5 0.5 to 2.5 mg/L. Recoveries were from 92 to 98% for FRC and from 97 to 106% TotheThis achieve sample paper sufficient into compares the analyzer.disinfection the Residual and Chlorineto minimize method any undesiredused by the byproducts, Gallery analyzer it is to the A hypochlorite wash is usually done as part of the discrete analyzer’s daily routine. If this 0.6 , mg/L 3.0 QC 0.1 mg/l TRC Low 0.09 92 % -0.01 0.09 90 % -0.01 1 % 0.4 2.0 forrecoveries TRC. The of smallest82% for QCFRC (0.1 and mg/L) 92% forwas TRC. close Results to the quantitationfor the reference limit andmethod showed were essential to monitor both free and combined residual chlorine concentrations in the water. occurredprotocol after is used, the last re-flushing reaction the component tubing is wasrecommended. added. Due A to zero the concentrationhigher temperature sample Results and Discussion 2.5 A hypochlorite wash is usually done as part of the discrete analyzer’s daily routine. If this , mg/L Thismanual paper method compares based the on Residual EPA 330.5 Chlorine and SFS method-EN ISOused 7393 by the-2:2000. Gallery analyzer to the 0.4 1.5 QCrecoveries82% 0.5 mg/l and 90%,ofTRC 82% Low respectively. for FRC0.48 and Low 92%97 %recoveries for TRC.-0.02 areResults thought0.49 for theto be99 reference %the result-0.01 method of evaporation were-2 % PO71657-EN 06/15S utilized,can also the be incubation measured time before is shorter sample compared analysis to theensure standard that all methods. residual Finally,analyte is fully 0.2 y = 0.946x – 0.009 2.0 y = 1. 005x – 0.025 protocol is used, re-flushing the tubing is recommended. A zero concentration sample Method Comparison Studies 1.0 of the analyte. manual method based on EPA 330.5 and SFS-EN ISO 7393-2:2000. absorbanceremoved from of the the reaction instrument. mixture was measured at 510 nm. r² = 0.992 1.5 r² = 0.998 QC82% 0.5 andmg/l 90%,FRC Highrespectively. 0.46 Low93 recoveries % -0.04 are thought0.51 to be102 the % result0.01 of evaporation-9 % PO71657-EN 06/15S Rapid Analysis Using the Gallery Analyzer STAT-Protocol can also be measured before sample analysis to ensure that all residual analyte is fully 0.2 y = 0.946x – 0.009 0.5 y = 1. 005x – 0.025 The0.0 Gallery analyzer FRC low andr² high= 0.992 concentration1.0 applications were comparedr² = 0.998 to ofIn the general, analyte Gallery. analyzer applications showed lower results than the reference All trademarks are the property of Thermo Fisher Scientific and its subsidiaries. FRCremoved applications from the (FRC instrument. Low an FRC High) are similar to TRC applications, but without 0.0 QC 1.0 mg/l FRC High 0.97 97 % -0.03 1.01 101 % 0.01 -5 %

Gallery Results, mg/L 0.0 0.2 0.4 0.6 0.5 The unstable nature of residual chlorine in water samples requires a rapid analysis the similar manual spectrophotometric analysis applications Results Gallery 0.0 and the1.0 results are2.0 shown 3.0 method, Chlorine Ref. This information is not intended to encourage use of these products in any manners that might infringe the 0.0 Reference Method, mg/L In general, Gallery analyzer applications showed lower results than the reference All trademarks are the property of Thermo Fisher Scientific and its subsidiaries. the addition of potassium iodide and the incubation step. 0.0 QC 2.5 mg/l FRC High 2.46 98 % -0.04 2.68 107 % 0.18 -8 % intellectual property rights of others. method. Thermo Scientific™ Gallery™ discrete analyzer offers a STAT-Protocol that below Gallery Results, mg/L 0.0 in Figures 20.2 and 3. 0.4 0.6 Reference Method, mg/L Results Gallery 0.0 1.0 2.0 3.0 method, Chlorine Ref. This information is not intended to encourage use of these products in any manners that might infringe the Reference Method, mg/L minimizes the exposure of samples to the atmosphere. In many water laboratories Combined residual chlorine (CRC) applications (CRC Low and CRC High) are QC 1.0 mg/l TRC High 0.98 98 % -0.02 1.05 105 % 0.05 -6 % intellectual property rights of others. Reference Method, mg/L the discrete analyzer runs non-stop, performing multiple analyses for various types of applications that subtract the FRC results from the TRC results. These calculations FIGURES 2-3. Method correlation of Gallery analyzer vs. manual DPD-photometric QC 2.5 mg/l TRC High 2.65 106 % 0.15 2.70 108 % 0.20 -2 % water samples simultaneously. When analyzing residual chlorine, it is recommended can be automatically performed with the Gallery analyzer. methods using FRC Low and FRC High applications. that the time a sample is in contact with the atmosphere is minimized. When using a Gallery discrete analyzer, a free residual chlorine analysis can be requested using the Contamination from other sample matrixes or reagents was not studied, therefore Both methods showed fairlygood to good recoveries from the QC samples between STAT-Protocol. As a result, the analysis will be performed immediately after inserting analyzing chlorine samples using the STAT-Protocol or by inserting samples one at a Method Correlation: FRC Low Method Correlation: FRC High

0.5 to 2.5 mg/L. Recoveries were from 92 to 98% for FRC and from 97 to 106% the sample into the analyzer. time is recommended. A laboratory can also validate the method for mixed runs. 0.6 3.0 for TRC. The smallest QC (0.1 mg/L) was close to the quantitation limit and showed 2.5 A hypochlorite wash is usually done as part of the discrete analyzer’s daily routine. If this , mg/L This paper compares the Residual Chlorine method used by the Gallery analyzer to the 0.4 recoveries of 82% for FRC and 92% for TRC. Results for the reference method were protocol is used, re-flushing the tubing is recommended. A zero concentration sample 2.0 manual method based on EPA 330.5 and SFS-EN ISO 7393-2:2000. 1.5 82% and 90%, respectively. Low recoveries are thought to be the result of evaporation PO71657-EN 06/15S can also be measured before sample analysis to ensure that all residual analyte is fully 0.2 y = 0.946x – 0.009 y = 1. 005x – 0.025 r² = 0.992 1.0 r² = 0.998 of the analyte. removed from the instrument. 0.5 0.0 In general, Gallery analyzer applications showed lower results than the reference All trademarks are the property of Thermo Fisher Scientific and its subsidiaries. 0.0

Gallery Results, mg/L 0.0 0.2 0.4 0.6 Gallery Results Gallery 0.0 1.0 2.0 3.0 method, Chlorine Ref. This information is not intended to encourage use of these products in any manners that might infringe the Reference Method, mg/L Reference Method, mg/L intellectual property rights of others.

Easy and Rapid Application for Residual Chlorine Analysis in Water Samples Marita Jokinen and Annu Suoniemi-Kähärä * ThermoEasy andFisher Rapid Scientific, Application Vantaa, Finland for Residual Chlorine Analysis in Water Samples *author, [email protected] Marita Jokinen and Annu Suoniemi-Kähärä * Thermo Fisher Scientific, Vantaa, Finland Reagent Preparation for Gallery Analyzer The Gallery analyzer TRC low and high concentration applications were compared to Introduction*author, annu.suoniemi [email protected] and Methods the similar manual spectrophotometric analysis applications and the results are shown Conclusion Reagents RC R1, RC R2, and RC R3 were inserted into the analyzer approximately 30 Chlorine is commonly used for disinfection in a wide range of applications. For below in Figures 4 and 5. This study shows that TRC can be measured using the discrete analyzer, and the Method Principle minutes before the required analysis to ensure adequate stabilization of the reagents. sanitizing the water in swimming pools, chlorine is added in the form of sodium or Gallery method correlates very well with the EPA 330.5 and SFS-EN ISO 7393-2:2000 Reagents in the analyzer vials were replaced each day. Reagents RC R1 and RC R2 potassium hypochlorite or chlorine gas. Free residual chlorine (FRC) reacts instantly with the N,N-diphenyl-p-phenylene diamine FIGURES 4-5. Method correlation of Gallery analyzer vs. manual DPD-photometric manual methods. Quality control sample recoveries varied from 92 to 106%. The water were refrigerated, and the reagent RC R2 was protected from light. Reagent RC R2 (DPD) indicator to produce a red color in a pH range of 6.2 to 6.5. Absorbance is methods using TRC Low and TRC High applications. samples tested originated from several swimming pools and their concentrations were Immediately after its addition to water, a part of the chlorine reacts with manganese, showedReagent no visiblePreparation sign of for aging Gallery (a pink Analyzer color) during the two weeks of storage. Reagent The Gallery analyzer TRC low and high concentration applications were compared to measured at a wavelength of 510 nm. between 0.11 to 2.89 mg/L, including the spiked samples. Gallery applications are sulfides,Introduction or other organic compounds and is unavailable for disinfection. This part is Materials and Methods RC R3 was prepared daily. the similar manual spectrophotometric analysis applications and the results are shown Conclusion In the total residual chlorine (TRC) method, chlorine liberates iodine from potassium Reagents RC R1, RC R2, and RC R3 were inserted into the analyzer approximately 30 below in FiguresMethod 4Correlation: and 5. TRC Low Method Correlation: TRC High designed for concentration areas of 0.1 to 0.5 mg/L (low range) and 0.5 to 3.0 mg/L

calledChlorine the “chlorine is commonly demand used of for water” disinfection as shown in a in wide Figure range 1. of applications. For This study shows that TRC can be measured using the discrete analyzer, and the Method Principle Preliminaryminutes before tests usingthe required frozen reagentsanalysis toshowed ensure identical adequate results stabilization when compared of the reagents. to 0.7 3.5 (high range). sanitizing the water in swimming pools, chlorine is added in the form of sodium or iodide when an excess amount of iodine is present. The liberated iodine reacts with DPD Gallery method correlates very well with the EPA 330.5 and SFS-EN ISO 7393-2:2000 The portion remaining is called “active chlorine” or “total active chlorine.” Part of this refrigeratedReagents reagentsin the analyzer. vials were replaced each day. Reagents RC R1 and RC R2 0.6 3.0 potassium hypochlorite or chlorine gas. to Freeproduce residual a red chlorine-colored (FRC) solution. reacts Absorbance instantly iswith measured the N,N -atdiphenyl a wavelength-p-phenylene of 510 diamine nm. FIGURES 4-5. Method correlation of Gallery analyzer vs. manual DPD-photometric Themanual FRC methodmethods. also Quality correlates control well sample with SFSrecoveries-EN ISO varied 7393 from-2:2000 92 tomanual 106%. methods. The water total chlorine can react with certain nitrogenous compounds, mostly from sweat and (DPD) indicator to produce a red color in a pH range of 6.2 to 6.5. Absorbance is were refrigerated, and the reagent RC R2 was protected from light. Reagent RC R2 0.5 , mg/L 2.5 0.02 M KMnO4 Calibrator Stock Solution methods using TRC Low and TRC High applications. Testedsamples samples tested varied originated in concentration from several from swimming 0.12 to pools2.94 mg/L, and their including concentrations the spiked were urine,Immediately forming ammoniumafter its addition chlorides. to water, This a group part of of the compounds chlorine reacts is called with “combined manganese, Oxidizing agents interfere with the method and these are usually present in very low showed no visible sign of aging (a pink color) during the two weeks of storage. Reagent 0.4 2.0 measured at a wavelength of 510 nm. samples.between However 0.11 to 2.89 the unstable mg/L, including nature ofthe FRC spiked offers samples. a challenge Gallery which applications was are concentrations compared to the residual chlorine concentrations. However, sunlight, 0.3 1.5 chlorine”sulfides, and or otherit is not organic as effective compounds a disinfectant and is unavailable as the “free for chlorine” disinfection. fraction, This which part is TheRC 0.02 R3 wasM potassium prepared permanganate daily. (KMnO4) calibrator stock solution is 3547 mg/L as y = 1.034x – 0.014 Results demonstrateddesigned for in concentration the low concentration areas of 0.1 area. to 0.5From mg/L the (lowQC samplerange) andof 0.1 0.5 mg/L, to 3.0 an mg/L exposureIn the total to air, residual and agitation chlorine of (TRC) the sample method, may chlorine critically liberates effect theiodine outcome. from potassium Therefore, 0.2 Method Correlation:r² TRC= 0.986 Low 1.0 Method Correlation:y = 1.049x TRC - 0.034 High consistscalled theof hypochlorite “chlorine demand ions, hypochlorous of water” as shown acid, and in Figure chlorine 1. gas. equivalent to Chlorine. The solution was prepared from a commercial concentrate. Preliminary tests using frozen reagents showed identical results when compared to 0.7 3.5 r² = 0.997 82%(high recovery range). was also shown with the reference method. Other QC samples showed a quickiodide analysis when an of excess the free amount residual of chlorineiodine is is present. essential. The Turbidity liberated and iodine color reacts may alsowith DPD 0.1 0.5 Gallery Gallery Results, mg/L The portion remaining is called “active chlorine” or “total active chlorine.” Part of this A KMnOrefrigerated4 solution reagents is often. used in calibrating the residual chlorine method because it is 0.6 Gallery 3.0 good recoveries ranging from 92% to 98%. interfereto produce with acolorimetric red-colored analysis solution. and Absorbance this can be is avoided measured by atapplication a wavelength design. of 510A high nm. 0.0 0.0 The FRC method also correlates well with SFS-EN ISO 7393-2:2000 manual methods. 0.5 , mg/L 2.5 FIGUREtotal chlorine 1. Chemical can react reactions with certain in water nitrogenous chlorination. compounds, mostly from sweat and more stable than an active chlorine solution. The permanganate ion oxidizes the DPD 0.0 0.2 0.4 0.6 0.0 1.0 2.0 3.0 concentration of monochloramine can interfere with free chlorine determination. With 0.02 M KMnO4 Calibrator Stock Solution Tested samples varied in concentration from 0.12 to 2.94 mg/L, including the spiked urine, forming ammonium chlorides. This group of compounds is called “combined Oxidizing agents interfere with the method and these are usually present in very low 0.4 Reference Method, mg/L 2.0 these samples; the application can be redesigned to avoid this by stopping the reaction molecule in the same way as any active chlorine compound. Reference Method, mg/L samples. However the unstable nature of FRC offers a challenge which was concentrations compared to the residual chlorine concentrations. However, sunlight, 0.3 1.5 chlorine” and it is not as effective a disinfectant as the “free chlorine” fraction, which The 0.02 M potassium permanganate (KMnO4) calibrator stock solution is 3547 mg/L as y = 1.034x – 0.014 Results References with arsenite or thioacetamide. demonstrated in the low concentration area. From the QC sample of 0.1 mg/L, an exposure to air, and agitation of the sample may critically effect the outcome. Therefore, This solution is stable for up to 12 months if tightly sealed and refrigerated in an amber 0.2 r² = 0.986 1.0 y = 1.049x - 0.034 consists of hypochlorite ions, hypochlorous acid, and chlorine gas. equivalent to Chlorine. The solution was prepared from a commercial concentrate. r² = 0.997 4 82%1. US recovery EPA, Methods was also for shown Chemical with theAnalysis reference of Water method. and OtherWastes QC, Method samples 330.5 showed Equipmena quick analysist of the free residual chlorine is essential. Turbidity and color may also bottle in the dark. KMnO is light sensitive and degrades over time (especially at low According0.1 to these method comparison studies, all TRC0.5 methods correlated well with each Gallery Gallery Results, mg/L

Gallery Gallery Chlorine, Total Residual (Spectrophotometric, DPD), 1978: 330 5-1. interfere with colorimetric analysis and this can be avoided by application design. A high concentrationsA KMnO4 solution). is often used in calibrating the residual chlorine method because it is other 0.0with no significant systematic error as shown in Figures 4 and 5. The average bias in good recoveries ranging from 92% to 98%. A Thermo Scientific Gallery, Gallery Plus, or Aquakem™ analyzer can be used. The 0.0 FIGURE 1. Chemical reactions in water chlorination. concentration of monochloramine can interfere with free chlorine determination. With more stable than an active chlorine solution. The permanganate ion oxidizes the DPD this evaluation0.0 was0.2 2.1 % for0.4 the lower0.6 concentration area0.0 (0.1 to 1.00.5 mg/L)2.0 and 4.9 3.0% for 2. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; method in this paper was performed with the Gallery analyzer measured at a wavelength The calibration may be performed by separate calibrators when the dilution is done Reference Method, mg/L these samples; the application can be redesigned to avoid this by stopping the reaction molecule in the same way as any active chlorine compound. the higher concentration area (0.5 to 3.0 mg/L). Reference Method, mg/L Baird, R.B.; Eaton, A.D., Eds. 4500-CL (A) Introduction, American Public Health of 510 nm. manually, or by serial calibration when the dilution series is done automatically by the References with arsenite or thioacetamide. GalleryThis solution or Aquakem is stable analyzer. for up to 12 months if tightly sealed and refrigerated in an amber Analysis of low concentration FRC methods in this study was fairly good as shown in Association, 22nd Edition, 2012. Gallery Application 1. US EPA, Methods for Chemical Analysis of Water and Wastes, Method 330.5 Equipment bottle in the dark. KMnO4 is light sensitive and degrades over time (especially at low FiguresAccording 2 and to 3. these The methodaverage comparison bias was -5.4 studies, % for theall TRC low rangemethods and correlated 0.5 % for wellthe high with each 3. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; Working KMnO4-solutions Chlorine, Total Residual (Spectrophotometric, DPD), 1978: 330 5-1. Gallery applications are based on EPA 330.5 for the TRC measurement. This method is concentrations). range.other However, with no significant some of thesystematic individual error results as shown deviated in Figuressignificantly, 4 and as 5. much The average as -26 % bias in Baird, R.B.; Eaton, A.D., Eds. 4500-CL (F) DPD Ferrous Titrimetric Method, A Thermo Scientific Gallery, Gallery Plus, or Aquakem™ analyzer can be used. The similar to SFS-EN ISO 7393-2:2000 for both TRC and FRC. Differences in the official A 12 mg/L equivalent Chlorine standard was prepared for High Range calibration fromthis the evaluation reference was results. 2.1 % This for themay lower be due concentration to the nature area of the(0.1 analyte to 0.5 mg/L)or delays and in4.9 the % for 2.American Standard Public Methods Health for Association,the Examination 22nd of Edition, Water and2012 Wastewater,. Rice, E.W.; method in this paper was performed with the Gallery analyzer measured at a wavelength The calibration may be performed by separate calibrators when the dilution is done methods and the Gallery applications are shown in Table 1. (0.5 to 3 mg/L) and a 1.5 mg/L equivalent Chlorine standard for Low Range analysisthe higher of samples. concentration Therefore, area inserting(0.5 to 3.0 the mg/L). FRC samples one at a time or using the Baird, R.B.; Eaton, A.D., Eds. 4500-CL (A) Introduction, American Public Health of 510 nm. manually, or by serial calibration when the dilution series is done automatically by the 4. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; (0.1 to 0.5 mg/L) calibration. STAT-Protocol is recommended. Association, 22nd Edition, 2012. Gallery or Aquakem analyzer. Analysis of low concentration FRC methods in this study was fairly good as shown in Baird, R.B.; Eaton, A.D., Eds. 4500-CL (G) DPD Colorimetric Method, American Gallery Application Table 1. Comparison of residual chlorine methods. Sample Analysis and Sample types DuringFigures the 2 analysis and 3. The of free average residual bias chlorine, was -5.4 it %was for noticed the low that range the and highest 0.5 %evaporation for the high (%) 3.Public Standard Health Methods Association, for the 22nd Examination Edition, 2012 of Water. and Wastewater, Rice, E.W.; Working KMnO4-solutions Gallery applications are based on EPA 330.5 for the TRC measurement. This method is wasrange. detected However, from lowsome concentration of the individual samples. results Therefore, deviated forsignificantly, future analysis, as much analyte as -26 % Baird, R.B.; Eaton, A.D., Eds. 4500-CL (F) DPD Ferrous Titrimetric Method, SFS-EN ISO Gallery Chlorine Ref Samples were taken from several public swimming pools. Sample concentrations were 5. Wendelken, S.C.; Losh, D.E.; Fair, P.S. Method 334.0: Determination of Residual similar to SFS-EN ISOEPA 7393 330.5-2:2000 for both TRC and FRC. Differences in the official A 12 mg/L equivalent Chlorine standard was prepared for High Range calibration evaporationfrom the reference from the results.samples This should may be be minimized due to the by nature using of 10 the mL analyte test tubes or delays which in are the American Public Health Association, 22nd Edition, 2012. 7393-2:2000 Application (TFS R&D) from 0.12 to 0.58 mg/L for FRC and 0.11 to 0.89 mg/L for TRC. To cover the whole Chlorine in Drinking Water using an On-line Chlorine Analyzer, Version 1.0; methods and the Gallery applications are shown in Table 1. (0.5 to 3 mg/L) and a 1.5 mg/L equivalent Chlorine standard for Low Range filledanalysis to 1/3 of of samples. their full volume.Therefore, inserting the FRC samples one at a time or using the concentration range of the calibration (0.1 to 3.0 mg/L), spike samples were prepared. 4.Office Standard of Ground Methods Water for and the DrinkingExamination Water, of WaterUS EPA: and Cincinnati, Wastewater, OH, Rice, 2009 E.W.;. potassium potassium iodate + potassium potassium (0.1 to 0.5 mg/L) calibration. STAT-Protocol is recommended. Calibrator Small volumes of potassium hypochlorite solution were added to a series of pool water . Baird, R.B.; Eaton, A.D., Eds. 4500-CL (G) DPD Colorimetric Method, American permanganate KI permanganate permanganate 6. Leasca, S. Peeing in the Pool: So Wrong—and Bad for our Health, Study Says, Table 1. Comparison of residual chlorine methods. samplesSample and Analysis the concentrations and Sample of types the spiked samples were analyzed in the method During the analysis of free residual chlorine, it was noticed that the highest evaporation (%) Public Health Association, 22nd Edition, 2012. comparison study. Spiked sample concentrations included 0.12 to 2.94 mg/L for FRC Qualitywas detected Control from low concentration Samples samples. Therefore, for future analysis, analyte March 11, 2014, LA Times, http://www.latimes.com/nation/la/sh/pee-in-the-pool- KI in calibrator, FRC: No KI, no No KI, no no KI, no SFS-EN ISO Gallery Chlorine Ref Samples were taken from several public swimming pools. Sample concentrations were 5.20140311 Wendelken-story.html, S.C.; Losh [Online], D.E.; (Accessed Fair, P.S. May Method 5, 2015). 334.0: Determination of Residual Calibration EPA 330.5 incubation 2 min, incubation incubation, same and 0.11 to 2.89 mg/L for TRC. Eachevaporation application from had the low samples and high should quality be control minimized (QC) by samples. using 10 QC mL samples test tubes were which are incubation, 7393-2:2000 Application (TFS R&D) from 0.12 to 0.58 mg/L for FRC and 0.11 to 0.89 mg/L for TRC. To cover the whole Chlorine in Drinking Water using an On-line Chlorine Analyzer, Version 1.0; method same calibration for TRC: KI, 1 min calibration for FRC measuredfilled to 1/3 by ofboth their the full Gallery volume. analyzer Residual Chlorine applications and the manual 7. Krans, B. Why peeing in the pool is chemical warfare, March 31, 2104, Healthline calibration for TRC Qualityconcentration control samples range of for the this calibration study were (0.1 prepared to 3.0 mg/L), from spikesodium samples hypochlorite were prepared.solution ° Office of Ground Water and Drinking Water, US EPA: Cincinnati, OH, 2009. potassium FRCpotassium and TRC iodate + (37 C)potassium incubation andpotassium TRC spectrophotometric reference method (Chlorine Ref). Results are shown in Table 2. News, http://www.healthline.com/health-news/peeing-in-the-pool-is-chemical- Calibrator (freeSmall chlorine), volumes which of potassium was verified hypochlorite the same solutionday by sodium were added thiosulphate to a series titration. of pool water . permanganate KI permanganate permanganate samples and the concentrations of the spiked samples were analyzed in the method 6.warfare Leasca-033114.html, S. Peeing in[Online] the Pool: (Accessed So Wrong May— and5, 2015). Bad for our Health, Study Says, The intended purpose of chlorination is to kill the microorganisms and bacteria that are Wavelength 515 nm 510 nm 510 nm 510 nm Referencecomparison Method study. UsedSpiked for sample the Study concentrations included 0.12 to 2.94 mg/L for FRC Quality Control Samples March 11, 2014, LA Times, http://www.latimes.com/nation/la/sh/pee-in-the-pool- KI in calibrator, FRC: No KI, no No KI, no Table 2. QC sample results with Gallery applications and Chlorine Ref 2. 8. Chloramines- Combined Chlorine Problems, 2011, Pool Wizard, harmful to people. However, it may also create some undesired byproducts, such as no KI, no 20140311-story.html [Online] (Accessed May 5, 2015). KI (%)Calibration in reaction incubation 2 min, incubation incubation, same Evaluationand 0.11 ofto the2.89 Residual mg/L for Chlorine TRC. methods was done in the Thermo Fisher Scientific Each application had low and high quality control (QC) samples. QC samples were http://www.poolwizard.net/problems/chloramines.htm [Online] carcinogenic trichloromethane (chloroform), mono-, di- and tri-chloroacetic acids, or 1.00incubation, % 1.00 % 0.83 % 0.83 % mixturemethod same calibration for TRC: KI, 1 min calibration for FRC Finland R&D laboratory using the Gallery discrete analyzer. In this evaluation, a series of measured by both the Gallery analyzer Residual Chlorine applications and the manual 7.(Accessed Krans, B. May Why 5, peeing 2015). in the pool is chemical warfare, March 31, 2104, Healthline trichloramines, and highly toxic cyanogen chloride which are formed when chlorine is calibration for TRC Quality control samples for this study were prepared from sodium hypochlorite solution Gallery Applications Chlorine Ref FRC and TRC (37°C) incubation and TRC samples were measured against a manual DPD-spectrophotometric method (Chlorine spectrophotometric reference method (Chlorine Ref). Results are shown in Table 2. News, http://www.healthline.com/health-news/peeing-in-the-pool-is-chemical- combined with uric acid. (free chlorine), which was verified the same day by sodium thiosulphate titration. Bias Ref) based on EPA 330.5 TRC measurement. The major difference is the EPA method Sample\ Analyte Result, (Methods) warfare-033114.html [Online] (Accessed May 5, 2015). 515 nm 510 nm 510 nm 510 nm Recovery Bias Result Recovery Bias The intended purpose of chlorination is to kill the microorganisms and bacteria that are In the WavelengthGallery TRC applications (TRC Low (0.1 to 0.5 mg/L) and TRC High (0.5 to doesReference not measure Method free Used chlorine. for theThis Study manual reference method is similar to SFS-EN ISO Avg. % Combined chlorine in the water of swimming pools is often a symptom of an inadequate Table 2. QC sample results with% Gallerymg/L applications mg/L and %Chlorine mg/L Ref 2. 8. Chloramines- Combined Chlorine Problems, 2011, Pool Wizard, harmful to people. However, it may also create some undesired byproducts, such as 3 mg/L)), 6 µL of the phosphate buffer (RC R1) and 6 µl of the DPD indicator reagent 7393-2:2000 which determines both total and free residual chlorine. A Thermo Scientific mg/L amount of free chlorine. This may cause unwanted effects, such as skin irritation, KI (%) in reaction Evaluation of the Residual Chlorine methods was done in the Thermo Fisher Scientific http://www.poolwizard.net/problems/chloramines.htm [Online] carcinogenic trichloromethane (chloroform), mono-, di- and tri-chloroacetic acids, or (RC R2) were automatically1.00 added % to a disposable1.00 % cuvette. This0.83 was % followed by0.83 an % Multiskan™ GO Spectrophotometer was used for the manual measurements at a breathing difficulties, and a strong odor. Therefore, it is preferred that the amount of Finland R&D laboratory using the Gallery discrete analyzer. In this evaluation, a series of QC 0.1 mg/l FRC Low 0.08 82 % -0.02 0.08 82 % -0.02 1 % (Accessed May 5, 2015). trichloramines, and highly toxic cyanogen chloride which are formed when chlorine is mixture wavelength of 510 nm. Gallery Applications Chlorine Ref combined chlorine is as low as possible. automatic addition of 120 µL of sample and potassium iodide solution (RC R3). In the samples were measured against a manual DPD-spectrophotometric method (Chlorine combined with uric acid. TRC Low application, the sample was introduced first and RC R3 next. In the TRC High QC 0.5 mg/l FRC Low 0.46 92 % -0.04 0.51 102 % 0.01 -9 Bias% Ref) based on EPA 330.5 TRC measurement. The major difference is the EPA method Sample\ Analyte Result, (Methods) application, this was done in the reverse order. An incubation for 60 seconds at 37°C Recovery Bias Result Recovery Bias To achieve sufficient disinfection and to minimize any undesired byproducts, it is In the Gallery TRC applications (TRC Low (0.1 to 0.5 mg/L) and TRC High (0.5 to does not measure free chlorine. This manual reference method is similar to SFS-EN ISO QC 0.1 mg/l TRC Low 0.09Avg. 92 % -0.01 0.09 90 % -0.01 1 %% Combined chlorine in the water of swimming pools is often a symptom of an inadequate occurred after the last reaction component was added. Due to the higher temperature % mg/L mg/L % mg/L essential to monitor both free and combined residual chlorine concentrations in the water. 3 mg/L)), 6 µL of the phosphate buffer (RC R1) and 6 µl of the DPD indicator reagent Results7393-2:2000 whichand determines Discussion both total and free residual chlorine. A Thermo Scientific mg/L amount of free chlorine. This may cause unwanted effects, such as skin irritation, utilized, the incubation time is shorter compared to the standard methods. Finally, QC 0.5 mg/l TRC Low 0.48 97 % -0.02 0.49 99 % -0.01 -2 % (RC R2) were automatically added to a disposable cuvette. This was followed by an MethodMultiskan Comparison™ GO Spectrophotometer Studies was used for the manual measurements at a breathing difficulties, and a strong odor. Therefore, it is preferred that the amount of absorbance of the reaction mixture was measured at 510 nm. QCQC 0.5 0.1 mg/l mg/l FRCFRC High Low 0.460.08 93 82% % -0.04-0.02 0.510.08 10282 % % 0.01-0.02 -9 %1 % Rapid Analysis Using the Gallery Analyzer STAT-Protocol automatic addition of 120 µL of sample and potassium iodide solution (RC R3). In the wavelength of 510 nm. combined chlorine is as low as possible. The Gallery analyzer FRC low and high concentration applications were compared to FRCTRC applications Low application, (FRC Low the samplean FRC wasHigh) introduced are similar first to andTRC RC applications, R3 next. In but the without TRC High QCQC 1.0 0.5 mg/l mg/l FRCFRC High Low 0.970.46 97 92% % -0.03-0.04 1.010.51 101102 % % 0.010.01 -5 %-9 % The unstable nature of residual chlorine in water samples requires a rapid analysis the similar manual spectrophotometric analysis applications and the results are shown theapplication, addition of this potassium was done iodide in the and reverse the incubation order. An step. incubation for 60 seconds at 37°C method.To achieve Thermo sufficient Scientific™ disinfection Gallery™ and discreteto minimize analyzer any undesired offers a STATbyproducts,-Protocol it isthat below in Figures 2 and 3. QCQC 2.5 0.1 mg/l mg/l FRCTRC High Low 2.460.09 98 92% % -0.04-0.01 2.680.09 10790 % % 0.18-0.01 -8 %1 % occurred after the last reaction component was added. Due to the higher temperature Results and Discussion minimizesessential the to monitorexposure both of samplesfree and tocombined the atmosphere. residual chlorineIn many concentrationswater laboratories in the water. Combined residual chlorine (CRC) applications (CRC Low and CRC High) are QC 0.5 mg/l TRC Low 0.48 97 % -0.02 0.49 99 % -0.01 -2 % utilized, the incubation time is shorter compared to the standard methods. Finally, QC 1.0 mg/l TRC High 0.98 98 % -0.02 1.05 105 % 0.05 -6 % the discrete analyzer runs non-stop, performing multiple analyses for various types of applications that subtract the FRC results from the TRC results. These calculations Method Comparison Studies absorbance of the reaction mixture was measured at 510 nm. FIGURES 2-3. Method correlation of Gallery analyzer vs. manual DPD-photometric QC 0.5 mg/l FRC High 0.46 93 % -0.04 0.51 102 % 0.01 -9 % waterRapid samples Analysis simultaneously. Using the Gallery When analyzingAnalyzer residualSTAT-Protocol chlorine, it is recommended can be automatically performed with the Gallery analyzer. QC 2.5 mg/l TRC High 2.65 106 % 0.15 2.70 108 % 0.20 -2 % methodsThe Gallery using analyzer FRC Low FRC and low FRC and Highhigh concentration applications. applications were compared to that the time a sample is in contact with the atmosphere is minimized. When using a FRC applications (FRC Low an FRC High) are similar to TRC applications, but without QC 1.0 mg/l FRC High 0.97 97 % -0.03 1.01 101 % 0.01 -5 % Easy and Rapid Application for ResidualThe unstable nature ofChlorine residual chlorine in water Analysissamples requires a rapid analysisin WaterContamination Samples from other sample matrixes or reagents was not studied, therefore the similar manual spectrophotometric analysis applications and the results are shown Gallery discrete analyzer, a free residual chlorine analysis can be requested using the the addition of potassium iodide and the incubation step. method. Thermo Scientific™ Gallery™ discrete analyzer offers a STAT-Protocol that BothQC methods2.5 mg/l FRC showed High fairlygood2.46 to98 good% recoveries-0.04 from2.68 the QC107 %samples 0.18 between -8 % STAT-Protocol. As a result, the analysis will be performed immediately after inserting analyzing chlorine samples using the STAT-Protocol or by inserting samples one at a below inMethod Figures Correlation: 2 and 3. FRC Low Method Correlation: FRC High minimizes the exposure of samples to the atmosphere. In many water laboratories timeCombined is recommended. residual chlorine A laboratory (CRC) can applications also validate (CRC the Low method and CRCfor mixed High) runs. are 0.5QC to 1.0 2.5 mg/l mg/L. TRC Recoveries High 0.98 were from98 % 92 to -0.0298% for FRC1.05 and 105from % 97 to0.05 106% -6 % Easy and Rapid Application for Residualthe sample into the analyzer. Chlorine Analysis in Water Samples 0.6 3.0 Marita Jokinen and Annu Suoniemi-Kähärä the* discrete analyzer runs non-stop, performing multiple analyses for various types of applications that subtract the FRC results from the TRC results. These calculations for TRC. The smallest QC (0.1 mg/L) was close to the quantitation limit and showed FIGURES 2-3. Method correlation of Gallery analyzer2.5 vs. manual DPD-photometric A hypochlorite wash is usually done as part of the discrete analyzer’s daily routine. If this , mg/L QC 2.5 mg/l TRC High 2.65 106 % 0.15 2.70 108 % 0.20 -2 % Thiswater paper samples compares simultaneously. the Residual When Chlorine analyzing method residual used by chlorine, the Gallery it is recommended analyzer to the can be automatically performed with the Gallery analyzer. 0.4 recoveries of 82% for FRC and 92% for TRC. Results for the reference method were protocol is used, re-flushing the tubing is recommended. A zero concentration sample methods using FRC Low and FRC High applications.2.0 Thermo Fisher Scientific, Vantaa, Finland manualthat the method time abased sample on isEPA in contact 330.5 and with SFS the -atmosphereEN ISO 7393 is- 2:2000.minimized. When using a 1.5 82% and 90%, respectively. Low recoveries are thought to be the result of evaporation PO71657 -EN 06/15S Marita Jokinen and Annu Suoniemi-Kähärä * canContamination also be measured from otherbefore sample sample matrixes analysis or to reagents ensure that was all not residual studied, analyte therefore is fully 0.2 y = 0.946x – 0.009 y = 1. 005x – 0.025 Gallery discrete analyzer, a free residual chlorine analysis can be requested using the 1.0 of the analyte. r² = 0.992 r² = 0.998 Both methods showed fairlygood to good recoveries from the QC samples between STAT-Protocol. As a result, the analysis will be performed immediately after inserting removedanalyzing from chlorine the instrument. samples using the STAT-Protocol or by inserting samples one at a Method Correlation: FRC Low 0.5 Method Correlation: FRC High

*author, [email protected] 0.0 All trademarks are the property of Thermo Fisher Scientific and its subsidiaries. Thermo Fisher Scientific, Vantaa, Finland time is recommended. A laboratory can also validate the method for mixed runs. 0.0 In 0.5general, to 2.5 Gallery mg/L. Recoveries analyzer applications were from showed92 to 98% lower for FRCresults and than from the 97 reference to 106% the sample into the analyzer. 0.6 3.0 Gallery Results, mg/L 0.0 0.2 0.4 0.6 Gallery Results Gallery 0.0 1.0 2.0 3.0 method,for TRC. Chlorine The smallest Ref. QC (0.1 mg/L) was close to the quantitation limit and showed This information is not intended to encourage use of these products in any manners that might infringe the Reference Method, mg/L 2.5 A hypochlorite wash is usually done as part of the discrete analyzer’s daily routine. If this , mg/L This paper compares the Residual Chlorine method used by the Gallery analyzer to the 0.4 Reference Method, mg/L recoveries of 82% for FRC and 92% for TRC. Results for the reference method were intellectual property rights of others. *author, [email protected] protocol is used, re-flushing the tubing is recommended. A zero concentration sample 2.0 manual method based on EPA 330.5 and SFS-EN ISO 7393-2:2000. 1.5 82% and 90%, respectively. Low recoveries are thought to be the result of evaporation PO71657-EN 06/15S can also be measured before sample analysis to ensure that all residual analyte is fully 0.2 y = 0.946x – 0.009 y = 1. 005x – 0.025 Reagent Preparation for Gallery Analyzer The Gallery analyzer TRC low and r²high = 0.992 concentration 1.0 applications were comparedr² = to 0.998 of the analyte. Introduction Materials and Methods removed from the instrument. the similar manual spectrophotometric analysis applications0.5 and the results are shown Conclusion 0.0 In general, Gallery analyzer applications showed lower results than the reference All trademarks are the property of Thermo Fisher Scientific and its subsidiaries. Reagents RC R1, RC R2, and RC R3 were inserted into the analyzer approximately 30 below in Figures 4 and 5. 0.0 Chlorine is commonly used for disinfection in a wide range of applications. For Gallery Results, mg/L 0.0 0.2 0.4 0.6 This study shows that TRC can be measured using the discrete analyzer, and the Method Principle minutes before the required analysis to ensure adequate stabilization of the reagents. The Gallery analyzer TRC low and high concentration Results Gallery 0.0 applications 1.0 were compared2.0 to 3.0 method, Chlorine Ref. This information is not intended to encourage use of these products in any manners that might infringe the sanitizing the water in swimming pools, chlorine is added in the form of sodium or Reagent Preparation for Gallery Analyzer Reference Method, mg/L Gallery method correlates very well with the EPA 330.5 and SFS-EN ISO 7393-2:2000 Introduction Materials and Methods Reagents in the analyzer vials were replaced each day. Reagents RC R1 and RC R2 the similar manual spectrophotometric analysis applications andReference the results Method, are mg/L shown Conclusion intellectual property rights of others. potassium hypochlorite or chlorine gas. Free residual chlorine (FRC) reacts instantly with the N,N-diphenyl-p-phenylene diamine Reagents RC R1, RC R2, and RC R3 were inserted into the analyzer approximately 30 FIGURES 4-5. Method correlation of Gallery analyzer vs. manual DPD-photometric manual methods. Quality control sample recoveries varied from 92 to 106%. The water Chlorine is commonly used for disinfection in a wide range of applications. For were refrigerated, and the reagent RC R2 was protected from light. Reagent RC R2 below in Figures 4 and 5. This study shows that TRC can be measured using the discrete analyzer, and the (DPD)Method indicator Principle to produce a red color in a pH range of 6.2 to 6.5. Absorbance is minutes before the required analysis to ensure adequate stabilization of the reagents. methods using TRC Low and TRC High applications. samples tested originated from several swimming pools and their concentrations were Immediatelysanitizing the after water its addition in swimming to water, pools, a part chlorine of the is chlorine added in reacts the form with of manganese, sodium or showed no visible sign of aging (a pink color) during the two weeks of storage. Reagent Gallery method correlates very well with the EPA 330.5 and SFS-EN ISO 7393-2:2000 measured at a wavelength of 510 nm. Reagents in the analyzer vials were replaced each day. Reagents RC R1 and RC R2 between 0.11 to 2.89 mg/L, including the spiked samples. Gallery applications are sulfides,potassium or other hypochlorite organic orcompounds chlorine gas. and is unavailable for disinfection. This part is Free residual chlorine (FRC) reacts instantly with the N,N-diphenyl-p-phenylene diamine RC R3 was prepared daily. FIGURES 4-5. Method correlation of Gallery analyzer vs. manual DPD-photometric manual methods. Quality control sample recoveries varied from 92 to 106%. The water In(DPD) the total indicator residual to chlorineproduce (TRC) a red colormethod, in a chlorine pH range liberates of 6.2 to iodine 6.5. Absorbance from potassium is were refrigerated, and the reagent RC R2 was protected from light. Reagent RC R2 Method Correlation: TRC Low Method Correlation: TRC High designed for concentration areas of 0.1 to 0.5 mg/L (low range) and 0.5 to 3.0 mg/L called the “chlorine demand of water” as shown in Figure 1. methods using TRC Low and TRC High applications. samples tested originated from several swimming pools and their concentrations were Immediately after its addition to water, a part of the chlorine reacts with manganese, Preliminaryshowed no tests visible using sign frozen of aging reagents (a pink showed color) during identical the results two weeks when of compared storage. Reagent to 0.7 3.5 (high range). iodidemeasured when atan a excess wavelength amount of 510of iodine nm. is present. The liberated iodine reacts with DPD between 0.11 to 2.89 mg/L, including the spiked samples. Gallery applications are The portion remaining is called “active chlorine” or “total active chlorine.” Part of this refrigerated reagents. 0.6 3.0 sulfides, or other organic compounds and is unavailable for disinfection. This part is to produce a red-colored solution. Absorbance is measured at a wavelength of 510 nm. RC R3 was prepared daily. The FRC method also correlates well with SFS-EN ISO 7393-2:2000 manual methods. total chlorine can react with certain nitrogenous compounds, mostly from sweat and In the total residual chlorine (TRC) method, chlorine liberates iodine from potassium 0.5 Method Correlation: TRC Low , mg/L 2.5 Method Correlation: TRC High designed for concentration areas of 0.1 to 0.5 mg/L (low range) and 0.5 to 3.0 mg/L

called the “chlorine demand of water” as shown in Figure 1. 0.02 M KMnO4 Calibrator Stock Solution 0.7 3.5 Tested samples varied in concentration from 0.12 to 2.94 mg/L, including the spiked urine, forming ammonium chlorides. This group of compounds is called “combined Oxidizingiodide when agents an interfereexcess amount with the of method iodine isand present. these Theare usuallyliberated present iodine in reacts very lowwith DPD Preliminary tests using frozen reagents showed identical results when compared to 0.4 2.0 (high range). 0.6 3.0 samples. However the unstable nature of FRC offers a challenge which was The portion remaining is called “active chlorine” or “total active chlorine.” Part of this concentrations compared to the residual chlorine concentrations. However, sunlight, refrigerated reagents. 0.3 1.5 chlorine” and it is not as effective a disinfectant as the “free chlorine” fraction, which to produce a red-colored solution. Absorbance is measured at a wavelength of 510 nm. The 0.02 M potassium permanganate (KMnO4) calibrator stock solution is 3547 mg/L as y = 1.034x – 0.014 Results The FRC method also correlates well with SFS-EN ISO 7393-2:2000 manual methods. total chlorine can react with certain nitrogenous compounds, mostly from sweat and exposure to air, and agitation of the sample may critically effect the outcome. Therefore, 0.20.5 r² = 0.986 , mg/L 2.5 y = 1.049x - 0.034 demonstrated in the low concentration area. From the QC sample of 0.1 mg/L, an consists of hypochlorite ions, hypochlorous acid, and chlorine gas. equivalent to Chlorine.4 The solution was prepared from a commercial concentrate. 1.0 Tested samples varied in concentration from 0.12 to 2.94 mg/L, including the spiked Oxidizing agents interfere with the method and these are usually present in very low 0.02 M KMnO Calibrator Stock Solution 0.4 2.0 r² = 0.997 82% recovery was also shown with the reference method. Other QC samples showed urine, forming ammonium chlorides. This group of compounds is called “combined a quick analysis of the free residual chlorine is essential. Turbidity and color may also 0.1 0.5

Gallery Gallery Results, mg/L samples. However the unstable nature of FRC offers a challenge which was concentrations compared to the residual chlorine concentrations. However, sunlight, 4 0.3 Gallery 1.5 good recoveries ranging from 92% to 98%. chlorine” and it is not as effective a disinfectant as the “free chlorine” fraction, which A TheKMnO 0.02 solution M potassium is often permanganate used in calibrating (KMnO the4) residualcalibrator chlorine stock solution method is because 3547 mg/L it is as y = 1.034x – 0.014 Results interfere with colorimetric analysis and this can be avoided by application design. A high 0.0 0.0 demonstrated in the low concentration area. From the QC sample of 0.1 mg/L, an FIGUREconsists 1. of Chemical hypochlorite reactions ions, hypochlorous in water chlorination. acid, and chlorine gas. exposure to air, and agitation of the sample may critically effect the outcome. Therefore, moreequivalent stable thanto Chlorine. an active The chlorine solution solution. was prepared The permanganate from a commercial ion oxidizes concentrate. the DPD 0.20.0 0.2 0.4 r² 0.6= 0.986 1.0 y = 1.049x - 0.034 concentration of monochloramine can interfere with free chlorine determination. With 0.0 1.0 2.0 r² = 0.9973.0 82% recovery was also shown with the reference method. Other QC samples showed a quick analysis of the free residual chlorine is essential. Turbidity and color may also molecule in the same way as any active chlorine compound. 0.1 Reference Method, mg/L 0.5 these samples; the application can be redesigned to avoid this by stopping the reaction Gallery Results, mg/L Reference Method, mg/L A KMnO4 solution is often used in calibrating the residual chlorine method because it is Gallery good recoveries ranging from 92% to 98%. withinterfere arsenite with or colorimetric thioacetamide analysis. and this can be avoided by application design. A high 0.0 0.0 References FIGURE 1. Chemical reactions in water chlorination. concentration of monochloramine can interfere with free chlorine determination. With Thismore solution stable is than stable an activefor up tochlorine 12 months solution. if tightly The sealedpermanganate and refrigerated ion oxidizes in an the amber DPD 0.0 0.2 0.4 0.6 0.0 1.0 2.0 3.0 Reference Method, mg/L 1. US EPA, Methods for Chemical Analysis of Water and Wastes, Method 330.5 Equipmenthese samples;t the application can be redesigned to avoid this by stopping the reaction bottlemolecule in the in dark. the sameKMnO way4 is lightas any sensitive active chlorineand degrades compound. over time (especially at low According to these method comparison studies, all TRC methodsReference correlated Method, well mg/L with each concentrations). other with no significant systematic error as shown in Figures 4 and 5. The average bias in ReferencesChlorine, Total Residual (Spectrophotometric, DPD), 1978: 330 5-1. A withThermo arsenite Scientific or thioacetamide Gallery, Gallery. Plus, or Aquakem™ analyzer can be used. The This solution is stable for up to 12 months if tightly sealed and refrigerated in an amber this evaluation was 2.1 % for the lower concentration area (0.1 to 0.5 mg/L) and 4.9 % for 2.1. StandardUS EPA, Methods Methods for for the Chemical Examination Analysis of Water of Water and and Wastewater, Wastes, Method Rice, E.W.; 330.5 method in this paper was performed with the Gallery analyzer measured at a wavelength Thebottle calibration in the dark. may KMnO be performed4 is light sensitiveby separate and calibrators degrades whenover time the dilution(especially is done at low According to these method comparison studies, all TRC methods correlated well with each Equipment the higher concentration area (0.5 to 3.0 mg/L). Baird, R.B.; Eaton, A.D., Eds. 4500-CL (A) Introduction, American Public Health of 510 nm. manually,concentrations or by serial). calibration when the dilution series is done automatically by the other with no significant systematic error as shown in Figures 4 and 5. The average bias in Chlorine, Total Residual (Spectrophotometric, DPD), 1978: 330 5-1. A Thermo Scientific Gallery, Gallery Plus, or Aquakem™ analyzer can be used. The Association, 22nd Edition, 2012. Gallery or Aquakem analyzer. Analysisthis evaluation of low concentration was 2.1 % for FRC the lowermethods concentration in this study area was (0.1 fairly to good0.5 mg/L) as shown and 4.9 in % for 2. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; Gallery Application The calibration may be performed by separate calibrators when the dilution is done method in this paper was performed with the Gallery analyzer measured at a wavelength Figuresthe higher 2 and concentration 3. The average area bias (0.5 was to 3.0 -5.4 mg/L). % for the low range and 0.5 % for the high 3. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; Workingmanually, KMnO or by4 -serialsolutions calibration when the dilution series is done automatically by the Baird, R.B.; Eaton, A.D., Eds. 4500-CL (A) Introduction, American Public Health Galleryof 510 applications nm. are based on EPA 330.5 for the TRC measurement. This method is range. However, some of the individual results deviated significantly, as much as -26 % Baird, R.B.; Eaton, A.D., Eds. 4500-CL (F) DPD Ferrous Titrimetric Method, Gallery or Aquakem analyzer. Analysis of low concentration FRC methods in this study was fairly good as shown in Association, 22nd Edition, 2012. similar to SFS-EN ISO 7393-2:2000 for both TRC and FRC. Differences in the official A 12 mg/L equivalent Chlorine standard was prepared for High Range calibration from the reference results. This may be due to the nature of the analyte or delays in the American Public Health Association, 22nd Edition, 2012. Gallery Application Figures 2 and 3. The average bias was -5.4 % for the low range and 0.5 % for the high 3. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; methods and the Gallery applications are shown in Table 1. (0.5Working to 3 mg/L) KMnO and4- solutionsa 1.5 mg/L equivalent Chlorine standard for Low Range analysis of samples. Therefore, inserting the FRC samples one at a time or using the Gallery applications are based on EPA 330.5 for the TRC measurement. This method is (0.1 to 0.5 mg/L) calibration. STATrange.-Protocol However, is recommended. some of the individual results deviated significantly, as much as -26 % 4. StandardBaird, R.B.; Methods Eaton, for A.D., the ExaminationEds. 4500-CL of (F) Water DPD and Ferrous Wastewater, Titrimetric Rice, Method, E.W.; similar to SFS-EN ISO 7393-2:2000 for both TRC and FRC. Differences in the official A 12 mg/L equivalent Chlorine standard was prepared for High Range calibration from the reference results. This may be due to the nature of the analyte or delays in the Baird,American R.B.; PublicEaton, Health A.D., Eds. Association, 4500-CL 22nd (G) DPD Edition, Colorimetric 2012. Method, American Table 1. Comparison of residual chlorine methods. methods and the Gallery applications are shown in Table 1. Sample(0.5 to Analysis3 mg/L) and and a Sample1.5 mg/L types equivalent Chlorine standard for Low Range Duringanalysis the of analysis samples. of freeTherefore, residual inserting chlorine, the it wasFRC noticed samples that one the at highest a time orevaporation using the (%) Public Health Association, 22nd Edition, 2012. was detected from low concentration samples. Therefore, for future analysis, analyte 4. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; Samples(0.1 to 0.5 were mg/L) taken calibration. from several public swimming pools. Sample concentrations were STAT-Protocol is recommended. SFS-EN ISO Gallery Chlorine Ref evaporation from the samples should be minimized by using 10 mL test tubes which are 5. WendelkenBaird, R.B.;, S.C.; Eaton, Losh A.D.,, D.E.; Eds. Fair, 4500 P.S.-CL Method (G) DPD 334.0: Colorimetric Determination Method, of AmericanResidual Table 1. ComparisonEPA of 330.5residual chlorine methods. from 0.12 to 0.58 mg/L for FRC and 0.11 to 0.89 mg/L for TRC. To cover the whole 7393-2:2000 Application (TFS R&D) Sample Analysis and Sample types filledDuring to 1/3 the of analysis their full of volume. free residual chlorine, it was noticed that the highest evaporation (%) ChlorinePublic Health in Drinking Association, Water using 22nd an Edition, On-line 2012 Chlorine. Analyzer, Version 1.0; concentration range of the calibration (0.1 to 3.0 mg/L), spike samples were prepared. was detected from low concentration samples. Therefore, for future analysis, analyte Office of Ground Water and Drinking Water, US EPA: Cincinnati, OH, 2009. potassium potassium iodate + potassium potassium Samples were taken from several public swimming pools. Sample concentrations were 5. Wendelken, S.C.; Losh, D.E.; Fair, P.S. Method 334.0: Determination of Residual Calibrator SFS-EN ISO Gallery Chlorine Ref Small volumes of potassium hypochlorite solution were added to a series of pool water . evaporation from the samples should be minimized by using 10 mL test tubes which are permanganateEPA 330.5 KI permanganate permanganate from 0.12 to 0.58 mg/L for FRC and 0.11 to 0.89 mg/L for TRC. To cover the whole 6. Leasca, S. Peeing in the Pool: So Wrong—and Bad for our Health, Study Says, 7393-2:2000 Application (TFS R&D) samples and the concentrations of the spiked samples were analyzed in the method filled to 1/3 of their full volume. Chlorine in Drinking Water using an On-line Chlorine Analyzer, Version 1.0; comparisonconcentration study. range Spiked of the sample calibration concentrations (0.1 to 3.0 included mg/L), spike 0.12 samplesto 2.94 mg/L were for prepared. FRC Quality Control Samples MarchOffice 11, of 2014,Ground LA Water Times, and http://www.latimes.com/nation/la/sh/pee Drinking Water, US EPA: Cincinnati, OH,-in- the2009-pool. - potassium potassiumKI in calibrator, iodate + FRC:potassium No KI, no Nopotassium KI, no Calibrator no KI, no Small volumes of potassium hypochlorite solution were added to a series of pool water . 20140311-story.html [Online] (Accessed May 5, 2015). Calibration permanganate incubationKI 2 min, permanganateincubation incubation,permanganate same and 0.11 to 2.89 mg/L for TRC. Each application had low and high quality control (QC) samples. QC samples were 6. Leasca, S. Peeing in the Pool: So Wrong—and Bad for our Health, Study Says, incubation, samples and the concentrations of the spiked samples were analyzed in the method method same calibration for TRC: KI, 1 min calibration for FRC measured by both the Gallery analyzer Residual Chlorine applications and the manual 7. Krans, B. Why peeing in the pool is chemical warfare, March 31, 2104, Healthline calibration for TRC Qualitycomparison control study. samples Spiked for thissample study concentrations were prepared included from sodium 0.12 to hypochlorite 2.94 mg/L forsolution FRC Quality Control Samples March 11, 2014, LA Times, http://www.latimes.com/nation/la/sh/pee-in-the-pool- FRCKI in and calibrator, TRC (37FRC:°C) incubation No KI, no andNo TRC KI, no spectrophotometric reference method (Chlorine Ref). Results are shown in Table 2. News, http://www.healthline.com/health-news/peeing-in-the-pool-is-chemical- no KI, no (free chlorine), which was verified the same day by sodium thiosulphate titration. 20140311-story.html [Online] (Accessed May 5, 2015). Calibration incubation 2 min, incubation incubation, same and 0.11 to 2.89 mg/L for TRC. Each application had low and high quality control (QC) samples. QC samples were incubation, warfare-033114.html [Online] (Accessed May 5, 2015). method same calibration for TRC: KI, 1 min calibration for FRC measured by both the Gallery analyzer Residual Chlorine applications and the manual 7. Krans, B. Why peeing in the pool is chemical warfare, March 31, 2104, Healthline The intended purpose of chlorination is to kill the microorganisms and bacteria that are Wavelength calibration515 nm for TRC 510 nm 510 nm 510 nm ReferenceQuality control Method samples Used for for this the study Study were prepared from sodium hypochlorite solution ° harmful to people. However, it may also create some undesired byproducts, such as FRC and TRC (37 C) incubation and TRC Tablespectrophotometric 2. QC sample resultsreference with method Gallery (Chlorine applications Ref). Results and Chlorine are shown Ref in 2. Table 2. 8. ChloraminesNews, http://www.healthline.com/health- Combined Chlorine Problems,-news/peeing 2011, Pool-in Wizard,-the-pool -is-chemical- Evaluation(free chlorine), of the which Residual was Chlorine verified themethods same wasday doneby sodium in the thiosulphate Thermo Fisher titration. Scientific carcinogenic trichloromethane (chloroform), mono-, di- and tri-chloroacetic acids, or KI (%) in reaction http://www.poolwizard.net/problems/chloramines.htmwarfare-033114.html [Online] (Accessed May 5, 2015). [Online] Wavelength 1.00515 % nm 1.00510 % nm 0.83510 % nm 0.83510 % nm Finland R&D laboratory using the Gallery discrete analyzer. In this evaluation, a series of trichloraminesThe intended, andpurpose highly of toxicchlorination cyanogen is to chloride kill the whichmicroorganisms are formed and when bacteria chlorine that is are mixture Reference Method Used for the Study Gallery Applications Chlorine Ref (Accessed May 5, 2015). samples were measured against a manual DPD-spectrophotometric method (Chlorine Table 2. QC sample results with Gallery applications and Chlorine Ref 2. 8. Chloramines- Combined Chlorine Problems, 2011, Pool Wizard, combinedharmful to with people. uric acid. However, it may also create some undesired byproducts, such as Bias KI (%) in reaction Evaluation of the Residual Chlorine methods was done in the Thermo Fisher Scientific http://www.poolwizard.net/problems/chloramines.htm [Online] carcinogenic trichloromethane (chloroform), mono-, di- and tri-chloroacetic acids, or 1.00 % 1.00 % 0.83 % 0.83 % Ref) based on EPA 330.5 TRC measurement. The major difference is the EPA method Sample\ Analyte Result, (Methods) mixture Finland R&D laboratory using the Gallery discrete analyzer. In this evaluation, a series of Recovery Bias Result Recovery Bias (Accessed May 5, 2015). trichloramines, and highly toxic cyanogen chloride which are formed when chlorine is In the Gallery TRC applications (TRC Low (0.1 to 0.5 mg/L) and TRC High (0.5 to does not measure free chlorine. This manual reference method is similar to SFS-EN ISO GalleryAvg. Applications Chlorine Ref % Combined chlorine in the water of swimming pools is often a symptom of an inadequate samples were measured against a manual DPD-spectrophotometric method (Chlorine % mg/L mg/L % mg/L combined with uric acid. 3 mg/L)), 6 µL of the phosphate buffer (RC R1) and 6 µl of the DPD indicator reagent 7393-2:2000 which determines both total and free residual chlorine. A Thermo Scientific mg/L Bias amount of free chlorine. This may cause unwanted effects, such as skin irritation, Ref) based on EPA 330.5 TRC measurement. The major difference is the EPA method Result, (RC R2) were automatically added to a disposable cuvette. This was followed by an Multiskan™ GO Spectrophotometer was used for the manual measurements at a Sample\ Analyte Recovery Bias Result Recovery Bias (Methods) breathing difficulties, and a strong odor. Therefore, it is preferred that the amount of does not measure free chlorine. This manual reference method is similar to SFS-EN ISO QC 0.1 mg/l FRC Low 0.08Avg. 82 % -0.02 0.08 82 % -0.02 1 %% Combined chlorine in the water of swimming pools is often a symptom of an inadequate automaticIn the Gallery addition TRC of applications 120 µL of sample (TRC Lowand potassium(0.1 to 0.5 iodidemg/L) solutionand TRC (RC High R3). (0.5 In to the wavelength of 510 nm. % mg/L mg/L % mg/L combined chlorine is as low as possible. 7393-2:2000 which determines both total and free residual chlorine. A Thermo Scientific mg/L amount of free chlorine. This may cause unwanted effects, such as skin irritation, TRC3 mg/L)), Low application, 6 µL of the phosphatethe sample buffer was introduced (RC R1) and first 6 and µl of RC the R3 DPD next. indicator In the TRCreagent High QC 0.5 mg/l FRC Low 0.46 92 % -0.04 0.51 102 % 0.01 -9 % (RC R2) were automatically added to a disposable cuvette. This was followed by an Multiskan™ GO Spectrophotometer was used for the manual measurements at a breathing difficulties, and a strong odor. Therefore, it is preferred that the amount of application, this was done in the reverse order. An incubation for 60 seconds at 37°C QC 0.1 mg/l FRC Low 0.08 82 % -0.02 0.08 82 % -0.02 1 % To achieve sufficient disinfection and to minimize any undesired byproducts, it is wavelength of 510 nm. QC 0.1 mg/l TRC Low 0.09 92 % -0.01 0.09 90 % -0.01 1 % combined chlorine is as low as possible. occurredautomatic after addition the last of reaction120 µL of component sample and was potassium added. Due iodide to thesolution higher (RC temperature R3). In the essential to monitor both free and combined residual chlorine concentrations in the water. Results and Discussion QC 0.5 mg/l FRC Low 0.46 92 % -0.04 0.51 102 % 0.01 -9 % utilized,TRC Low the application,incubation time the issample shorter was compared introduced to the first standard and RC methods.R3 next. In Finally, the TRC High QC 0.5 mg/l TRC Low 0.48 97 % -0.02 0.49 99 % -0.01 -2 % application, this was done in the reverse order. An incubation for 60 seconds at 37°C Method Comparison Studies To achieve sufficient disinfection and to minimize any undesired byproducts, it is absorbance of the reaction mixture was measured at 510 nm. QCQC 0.5 0.1 mg/l mg/l FRCTRC High Low 0.460.09 9392 % % -0.04-0.01 0.510.09 10290 % % 0.01-0.01 -9 1% % Rapid Analysis Using the Gallery Analyzer STAT-Protocol essential to monitor both free and combined residual chlorine concentrations in the water. occurred after the last reaction component was added. Due to the higher temperature TheResults Gallery analyzer and FRC Discussionlow and high concentration applications were compared to FRC applications (FRC Low an FRC High) are similar to TRC applications, but without QCQC 1.0 0.5 mg/l mg/l FRCTRC High Low 0.970.48 9797 % % -0.03-0.02 1.010.49 10199 % % 0.01-0.01 -5 -%2 % The unstable nature of residual chlorine in water samples requires a rapid analysis utilized, the incubation time is shorter compared to the standard methods. Finally, the similar manual spectrophotometric analysis applications and the results are shown the addition of potassium iodide and the incubation step. Method Comparison Studies method.Rapid AnalysisThermo Scientific™ Using the Gallery™Gallery Analyzer discrete STATanalyzer-Protocol offers a STAT-Protocol that absorbance of the reaction mixture was measured at 510 nm. below in Figures 2 and 3. QCQC 2.5 0.5 mg/l mg/l FRCFRC High High 2.460.46 9893 % % -0.04-0.04 2.680.51 107102 % % 0.180.01 -8 -%9 % The Gallery analyzer FRC low and high concentration applications were compared to minimizes the exposure of samples to the atmosphere. In many water laboratories CombinedFRC applications residual (FRCchlorine Low (CRC) an FRC applications High) are (CRC similar Low to TRCand CRCapplications, High) are but without QCQC 1.0 1.0 mg/l mg/l TRCFRC High High 0.980.97 9897 % % -0.02-0.03 1.051.01 105101 % % 0.050.01 -6 -%5 % The unstable nature of residual chlorine in water samples requires a rapid analysis the similar manual spectrophotometric analysis applications and the results are shown the discrete analyzer runs non-stop, performing multiple analyses for various types of applicationsthe addition that of potassiumsubtract the iodide FRC and results the fromincubation the TRC step. results. These calculations FIGURES 2-3. Method correlation of Gallery analyzer vs. manual DPD-photometric method. Thermo Scientific™ Gallery™ discrete analyzer offers a STAT-Protocol that below in Figures 2 and 3. QCQC 2.5 2.5 mg/l mg/l TRCFRC High High 2.652.46 10698 % % 0.15-0.04 2.702.68 108107 % % 0.200.18 -2 -%8 % water samples simultaneously. When analyzing residual chlorine, it is recommended can be automatically performed with the Gallery analyzer. methods using FRC Low and FRC High applications. minimizes the exposure of samples to the atmosphere. In many water laboratories Combined residual chlorine (CRC) applications (CRC Low and CRC High) are that the time a sample is in contact with the atmosphere is minimized. When using a QC 1.0 mg/l TRC High 0.98 98 % -0.02 1.05 105 % 0.05 -6 % the discrete analyzer runs non-stop, performing multiple analyses for various types of Contamination from other sample matrixes or reagents was not studied, therefore Gallery discrete analyzer, a free residual chlorine analysis can be requested using the applications that subtract the FRC results from the TRC results. These calculations FIGURES 2-3. Method correlation of Gallery analyzer vs. manual DPD-photometric BothQC 2.5methods mg/l TRC showed High fairlygood2.65 106to good% recoveries0.15 2.70from the 108QC % samples 0.20 between -2 % STATwater-Protocol. samples As simultaneously. a result, the analysis When analyzing will be performed residual immediatelychlorine, it is after recommended inserting analyzingcan be automatically chlorine samples performed using withthe STAT the Gallery-Protocol analyzer. or by inserting samples one at a methodsMethod using Correlation: FRC Low and FRC FRC Low High applications.Method Correlation: FRC High

0.5 to 2.5 mg/L. Recoveries were from 92 to 98% for FRC and from 97 to 106% thethat sample the time into a the sample analyzer. is in contact with the atmosphere is minimized. When using a time is recommended. A laboratory can also validate the method for mixed runs. 0.6 Gallery discrete analyzer, a free residual chlorine analysis can be requested using the Contamination from other sample matrixes or reagents was not studied, therefore 3.0 for TRC. The smallest QC (0.1 mg/L) was close to the quantitation limit and showed 2.5 A hypochlorite wash is usually done as part of the discrete analyzer’s daily routine. If this , mg/L Both methods showed fairlygood to good recoveries from the QC samples between ThisSTAT paper-Protocol. compares As a theresult, Residual the analysis Chlorine will method be performed used by immediately the Gallery afteranalyzer inserting to the analyzing chlorine samples using the STAT-Protocol or by inserting samples one at a 0.4 Method Correlation: FRC Low Method Correlation: FRC High recoveries of 82% for FRC and 92% for TRC. Results for the reference method were protocol time is is recommended. used, re-flushing A laboratory the tubing can is recommended. also validate the A zeromethod concentration for mixed runs. sample 2.0 0.5 to 2.5 mg/L. Recoveries were from 92 to 98% for FRC and from 97 to 106% manualthe sample method into based the analyzer. on EPA 330.5 and SFS-EN ISO 7393-2:2000. 0.6 1.53.0 82% and 90%, respectively. Low recoveries are thought to be the result of evaporation PO71657 -EN 06/15S can also be measured before sample analysis to ensure that all residual analyte is fully 0.2 y = 0.946x – 0.009 y = 1. 005x – 0.025 for TRC. The smallest QC (0.1 mg/L) was close to the quantitation limit and showed r² = 0.992 1.02.5 of the analyte. This paper compares the Residual Chlorine method used by the Gallery analyzer to the A hypochlorite wash is usually done as part of the discrete analyzer’s daily routine. If this , mg/L r² = 0.998 removed from the instrument. 0.4 0.52.0 recoveries of 82% for FRC and 92% for TRC. Results for the reference method were protocol is used, re-flushing the tubing is recommended. A zero concentration sample 0.0 In general, Gallery analyzer applications showed lower results than the reference All trademarks are the property of Thermo Fisher Scientific and its subsidiaries. manual method based on EPA 330.5 and SFS-EN ISO 7393-2:2000. 0.01.5 82% and 90%, respectively. Low recoveries are thought to be the result of evaporation PO71657-EN 06/15S

Gallery Results, mg/L 0.0 0.2 0.4 y = 0.946x – 0.0090.6 can also be measured before sample analysis to ensure that all residual analyte is fully 2 Easy0.2 and Rapid Application for Residual Chlorine Results Gallery 0.0 Analysis1.0 in Water2.0 ySamples = 1. 005x –3.0 0.025 method, Chlorine Ref. This information is not intended to encourage use of these products in any manners that might infringe the Reference Method, mg/L r² = 0.992 1.0 r² = 0.998 of the analyte. removed from the instrument. 0.5 Reference Method, mg/L intellectual property rights of others. 0.0 In general, Gallery analyzer applications showed lower results than the reference All trademarks are the property of Thermo Fisher Scientific and its subsidiaries. 0.0

Gallery Results, mg/L 0.0 0.2 0.4 0.6 Results Gallery 0.0 1.0 2.0 3.0 method, Chlorine Ref. This information is not intended to encourage use of these products in any manners that might infringe the Reference Method, mg/L Reference Method, mg/L intellectual property rights of others.

Easy and Rapid Application for Residual Chlorine Analysis in Water Samples Marita Jokinen and Annu Suoniemi-Kähärä * Thermo Fisher Scientific, Vantaa, Finland *author, [email protected]

Reagent Preparation for Gallery Analyzer The Gallery analyzer TRC low and high concentration applications were compared to Introduction Materials and Methods the similar manual spectrophotometric analysis applications and the results are shown Conclusion Reagents RC R1, RC R2, and RC R3 were inserted into the analyzer approximately 30 Chlorine is commonly used for disinfection in a wide range of applications. For below in Figures 4 and 5. This study shows that TRC can be measured using the discrete analyzer, and the Method Principle minutes before the required analysis to ensure adequate stabilization of the reagents. sanitizing the water in swimming pools, chlorine is added in the form of sodium or Gallery method correlates very well with the EPA 330.5 and SFS-EN ISO 7393-2:2000 Reagents in the analyzer vials were replaced each day. Reagents RC R1 and RC R2 potassium hypochlorite or chlorine gas. Free residual chlorine (FRC) reacts instantly with the N,N-diphenyl-p-phenylene diamine FIGURES 4-5. Method correlation of Gallery analyzer vs. manual DPD-photometric manual methods. Quality control sample recoveries varied from 92 to 106%. The water were refrigerated, and the reagent RC R2 was protected from light. Reagent RC R2 (DPD) indicator to produce a red color in a pH range of 6.2 to 6.5. Absorbance is methods using TRC Low and TRC High applications. samples tested originated from several swimming pools and their concentrations were Immediately after its addition to water, a part of the chlorine reacts with manganese, showed no visible sign of aging (a pink color) during the two weeks of storage. Reagent measured at a wavelength of 510 nm. between 0.11 to 2.89 mg/L, including the spiked samples. Gallery applications are sulfides, or other organic compounds and is unavailable for disinfection. This part is RC R3 was prepared daily. In the total residual chlorine (TRC) method, chlorine liberates iodine from potassium Method Correlation: TRC Low Method Correlation: TRC High designed for concentration areas of 0.1 to 0.5 mg/L (low range) and 0.5 to 3.0 mg/L

called the “chlorine demand of water” as shown in Figure 1. iodide when an excess amount of iodine is present. The liberated iodine reacts with DPD Preliminary tests using frozen reagents showed identical results when compared to 0.7 3.5 (high range). The portion remaining is called “active chlorine” or “total active chlorine.” Part of this refrigerated reagents. 0.6 3.0 to produce a red-colored solution. Absorbance is measured at a wavelength of 510 nm. The FRC method also correlates well with SFS-EN ISO 7393-2:2000 manual methods. total chlorine can react with certain nitrogenous compounds, mostly from sweat and 0.5 , mg/L 2.5 0.02 M KMnO4 Calibrator Stock Solution Tested samples varied in concentration from 0.12 to 2.94 mg/L, including the spiked urine, forming ammonium chlorides. This group of compounds is called “combined Oxidizing agents interfere with the method and these are usually present in very low 0.4 2.0 samples. However the unstable nature of FRC offers a challenge which was concentrations compared to the residual chlorine concentrations. However, sunlight, 0.3 1.5 chlorine” and it is not as effective a disinfectant as the “free chlorine” fraction, which The 0.02 M potassium permanganate (KMnO4) calibrator stock solution is 3547 mg/L as y = 1.034x – 0.014 Results demonstrated in the low concentration area. From the QC sample of 0.1 mg/L, an consists of hypochlorite ions, hypochlorous acid, and chlorine gas. exposure to air, and agitation of the sample may critically effect the outcome. Therefore, equivalent to Chlorine. The solution was prepared from a commercial concentrate. 0.2 r² = 0.986 1.0 y = 1.049x - 0.034 r² = 0.997 82% recovery was also shown with the reference method. Other QC samples showed a quick analysis of the free residual chlorine is essential. Turbidity and color may also 0.1 0.5 Gallery Gallery Results, mg/L A KMnO4 solution is often used in calibrating the residual chlorine method because it is Gallery good recoveries ranging from 92% to 98%. interfere with colorimetric analysis and this can be avoided by application design. A high 0.0 0.0 FIGURE 1. Chemical reactions in water chlorination. concentration of monochloramine can interfere with free chlorine determination. With more stable than an active chlorine solution. The permanganate ion oxidizes the DPD 0.0 0.2 0.4 0.6 0.0 1.0 2.0 3.0 Reference Method, mg/L these samples; the application can be redesigned to avoid this by stopping the reaction molecule in the same way as any active chlorine compound. Reference Method, mg/L References with arsenite or thioacetamide. This solution is stable for up to 12 months if tightly sealed and refrigerated in an amber 1. US EPA, Methods for Chemical Analysis of Water and Wastes, Method 330.5 Equipment bottle in the dark. KMnO4 is light sensitive and degrades over time (especially at low According to these method comparison studies, all TRC methods correlated well with each concentrations). other with no significant systematic error as shown in Figures 4 and 5. The average bias in Chlorine, Total Residual (Spectrophotometric, DPD), 1978: 330 5-1. A Thermo Scientific Gallery, Gallery Plus, or Aquakem™ analyzer can be used. The this evaluation was 2.1 % for the lower concentration area (0.1 to 0.5 mg/L) and 4.9 % for 2. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; method in this paper was performed with the Gallery analyzer measured at a wavelength The calibration may be performed by separate calibrators when the dilution is done the higher concentration area (0.5 to 3.0 mg/L). Baird, R.B.; Eaton, A.D., Eds. 4500-CL (A) Introduction, American Public Health of 510 nm. manually, or by serial calibration when the dilution series is done automatically by the Gallery or Aquakem analyzer. Analysis of low concentration FRC methods in this study was fairly good as shown in Association, 22nd Edition, 2012. Gallery Application Figures 2 and 3. The average bias was -5.4 % for the low range and 0.5 % for the high 3. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; Working KMnO4-solutions Gallery applications are based on EPA 330.5 for the TRC measurement. This method is range. However, some of the individual results deviated significantly, as much as -26 % Baird, R.B.; Eaton, A.D., Eds. 4500-CL (F) DPD Ferrous Titrimetric Method, similar to SFS-EN ISO 7393-2:2000 for both TRC and FRC. Differences in the official A 12 mg/L equivalent Chlorine standard was prepared for High Range calibration from the reference results. This may be due to the nature of the analyte or delays in the American Public Health Association, 22nd Edition, 2012. methods and the Gallery applications are shown in Table 1. (0.5 to 3 mg/L) and a 1.5 mg/L equivalent Chlorine standard for Low Range analysis of samples. Therefore, inserting the FRC samples one at a time or using the (0.1 to 0.5 mg/L) calibration. STAT-Protocol is recommended. 4. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; Baird, R.B.; Eaton, A.D., Eds. 4500-CL (G) DPD Colorimetric Method, American Table 1. Comparison of residual chlorine methods. Sample Analysis and Sample types During the analysis of free residual chlorine, it was noticed that the highest evaporation (%) Public Health Association, 22nd Edition, 2012. was detected from low concentration samples. Therefore, for future analysis, analyte Samples were taken from several public swimming pools. Sample concentrations were SFS-EN ISO Gallery Chlorine Ref evaporation from the samples should be minimized by using 10 mL test tubes which are 5. Wendelken, S.C.; Losh, D.E.; Fair, P.S. Method 334.0: Determination of Residual EPA 330.5 from 0.12 to 0.58 mg/L for FRC and 0.11 to 0.89 mg/L for TRC. To cover the whole 7393-2:2000 Application (TFS R&D) filled to 1/3 of their full volume. Chlorine in Drinking Water using an On-line Chlorine Analyzer, Version 1.0; concentration range of the calibration (0.1 to 3.0 mg/L), spike samples were prepared. Office of Ground Water and Drinking Water, US EPA: Cincinnati, OH, 2009. potassium potassium iodate + potassium potassium Calibrator Small volumes of potassium hypochlorite solution were added to a series of pool water . permanganate KI permanganate permanganate samples and the concentrations of the spiked samples were analyzed in the method 6. Leasca, S. Peeing in the Pool: So Wrong—and Bad for our Health, Study Says, comparison study. Spiked sample concentrations included 0.12 to 2.94 mg/L for FRC Quality Control Samples March 11, 2014, LA Times, http://www.latimes.com/nation/la/sh/pee-in-the-pool- KI in calibrator, FRC: No KI, no No KI, no no KI, no 20140311-story.html [Online] (Accessed May 5, 2015). Calibration incubation 2 min, incubation incubation, same and 0.11 to 2.89 mg/L for TRC. Each application had low and high quality control (QC) samples. QC samples were incubation, method same calibration for TRC: KI, 1 min calibration for FRC measured by both the Gallery analyzer Residual Chlorine applications and the manual 7. Krans, B. Why peeing in the pool is chemical warfare, March 31, 2104, Healthline calibration for TRC Quality control samples for this study were prepared from sodium hypochlorite solution FRC and TRC (37°C) incubation and TRC spectrophotometric reference method (Chlorine Ref). Results are shown in Table 2. News, http://www.healthline.com/health-news/peeing-in-the-pool-is-chemical- (free chlorine), which was verified the same day by sodium thiosulphate titration. warfare-033114.html [Online] (Accessed May 5, 2015). The intended purpose of chlorination is to kill the microorganisms and bacteria that are Wavelength 515 nm 510 nm 510 nm 510 nm Reference Method Used for the Study harmful to people. However, it may also create some undesired byproducts, such as Table 2. QC sample results with Gallery applications and Chlorine Ref 2. 8. Chloramines- Combined Chlorine Problems, 2011, Pool Wizard, Evaluation of the Residual Chlorine methods was done in the Thermo Fisher Scientific carcinogenic trichloromethane (chloroform), mono-, di- and tri-chloroacetic acids, or KI (%) in reaction http://www.poolwizard.net/problems/chloramines.htm [Online] 1.00 % 1.00 % 0.83 % 0.83 % Finland R&D laboratory using the Gallery discrete analyzer. In this evaluation, a series of trichloramines, and highly toxic cyanogen chloride which are formed when chlorine is mixture Gallery Applications Chlorine Ref (Accessed May 5, 2015). samples were measured against a manual DPD-spectrophotometric method (Chlorine combined with uric acid. Bias Ref) based on EPA 330.5 TRC measurement. The major difference is the EPA method Result, Sample\ Analyte Recovery Bias Result Recovery Bias (Methods) does not measure free chlorine. This manual reference method is similar to SFS-EN ISO Avg. % Combined chlorine in the water of swimming pools is often a symptom of an inadequate In the Gallery TRC applications (TRC Low (0.1 to 0.5 mg/L) and TRC High (0.5 to % mg/L mg/L % mg/L 7393-2:2000 which determines both total and free residual chlorine. A Thermo Scientific mg/L amount of free chlorine. This may cause unwanted effects, such as skin irritation, 3 mg/L)), 6 µL of the phosphate buffer (RC R1) and 6 µl of the DPD indicator reagent Multiskan™ GO Spectrophotometer was used for the manual measurements at a breathing difficulties, and a strong odor. Therefore, it is preferred that the amount of (RC R2) were automatically added to a disposable cuvette. This was followed by an wavelength of 510 nm. QC 0.1 mg/l FRC Low 0.08 82 % -0.02 0.08 82 % -0.02 1 % combined chlorine is as low as possible. automatic addition of 120 µL of sample and potassium iodide solution (RC R3). In the QC 0.5 mg/l FRC Low 0.46 92 % -0.04 0.51 102 % 0.01 -9 % TRC Low application, the sample was introduced first and RC R3 next. In the TRC High To achieve sufficient disinfection and to minimize any undesired byproducts, it is application, this was done in the reverse order. An incubation for 60 seconds at 37°C QC 0.1 mg/l TRC Low 0.09 92 % -0.01 0.09 90 % -0.01 1 % essential to monitor both free and combined residual chlorine concentrations in the water. occurred after the last reaction component was added. Due to the higher temperature Results and Discussion utilized, the incubation time is shorter compared to the standard methods. Finally, QC 0.5 mg/l TRC Low 0.48 97 % -0.02 0.49 99 % -0.01 -2 % Method Comparison Studies Rapid Analysis Using the Gallery Analyzer STAT-Protocol absorbance of the reaction mixture was measured at 510 nm. QC 0.5 mg/l FRC High 0.46 93 % -0.04 0.51 102 % 0.01 -9 % The Gallery analyzer FRC low and high concentration applications were compared to FRC applications (FRC Low an FRC High) are similar to TRC applications, but without QC 1.0 mg/l FRC High 0.97 97 % -0.03 1.01 101 % 0.01 -5 % The unstable nature of residual chlorine in water samples requires a rapid analysis the similar manual spectrophotometric analysis applications and the results are shown the addition of potassium iodide and the incubation step. method. Thermo Scientific™ Gallery™ discrete analyzer offers a STAT-Protocol that below in Figures 2 and 3. QC 2.5 mg/l FRC High 2.46 98 % -0.04 2.68 107 % 0.18 -8 % minimizes the exposure of samples to the atmosphere. In many water laboratories Combined residual chlorine (CRC) applications (CRC Low and CRC High) are QC 1.0 mg/l TRC High 0.98 98 % -0.02 1.05 105 % 0.05 -6 % the discrete analyzer runs non-stop, performing multiple analyses for various types of applications that subtract the FRC results from the TRC results. These calculations FIGURES 2-3. Method correlation of Gallery analyzer vs. manual DPD-photometric QC 2.5 mg/l TRC High 2.65 106 % 0.15 2.70 108 % 0.20 -2 % water samples simultaneously. When analyzing residual chlorine, it is recommended can be automatically performed with the Gallery analyzer. methods using FRC Low and FRC High applications. Easy and Rapid Application for Residualthat the time a sample isChlorine in contact with the atmosphere Analysis is minimized. When usingin a Water Samples Gallery discrete analyzer, a free residual chlorine analysis can be requested using the Contamination from other sample matrixes or reagents was not studied, therefore Both methods showed fairlygood to good recoveries from the QC samples between STAT-Protocol. As a result, the analysis will be performed immediately after inserting analyzing chlorine samples using the STAT-Protocol or by inserting samples one at a Method Correlation: FRC Low Method Correlation: FRC High

Marita Jokinen and Annu Suoniemi-Kähärä * 0.5 to 2.5 mg/L. Recoveries were from 92 to 98% for FRC and from 97 to 106% the sample into the analyzer. time is recommended. A laboratory can also validate the method for mixed runs. 0.6 3.0 for TRC. The smallest QC (0.1 mg/L) was close to the quantitation limit and showed 2.5 A hypochlorite wash is usually done as part of the discrete analyzer’s daily routine. If this , mg/L Thermo Fisher Scientific, Vantaa, Finland This paper compares the Residual Chlorine method used by the Gallery analyzer to the 0.4 recoveries of 82% for FRC and 92% for TRC. Results for the reference method were protocol is used, re-flushing the tubing is recommended. A zero concentration sample 2.0 manual method based on EPA 330.5 and SFS-EN ISO 7393-2:2000. 1.5 82% and 90%, respectively. Low recoveries are thought to be the result of evaporation PO71657-EN 06/15S can also be measured before sample analysis to ensure that all residual analyte is fully 0.2 y = 0.946x – 0.009 y = 1. 005x – 0.025 *author, [email protected] r² = 0.992 1.0 r² = 0.998 of the analyte. removed from the instrument. 0.5 0.0 In general, Gallery analyzer applications showed lower results than the reference All trademarks are the property of Thermo Fisher Scientific and its subsidiaries. 0.0

Gallery Results, mg/L 0.0 0.2 0.4 0.6 Gallery Results Gallery 0.0 1.0 2.0 3.0 method, Chlorine Ref. This information is not intended to encourage use of these products in any manners that might infringe the Reference Method, mg/L Reference Method, mg/L intellectual property rights of others. The Gallery analyzer TRC low and high concentration applications were compared to Reagent Preparation for Gallery Analyzer Introduction Materials and Methods the similar manual spectrophotometric analysis applications and the results are shown Conclusion Reagents RC R1, RC R2, and RC R3 were inserted into the analyzer approximately 30 Chlorine is commonly used for disinfection in a wide range of applications. For below in Figures 4 and 5. This study shows that TRC can be measured using the discrete analyzer, and the Method Principle minutes before the required analysis to ensure adequate stabilization of the reagents. sanitizing the water in swimming pools, chlorine is added in the form of sodium or Gallery method correlates very well with the EPA 330.5 and SFS-EN ISO 7393-2:2000 Reagents in the analyzer vials were replaced each day. Reagents RC R1 and RC R2 potassium hypochlorite or chlorine gas. Free residual chlorine (FRC) reacts instantly with the N,N-diphenyl-p-phenylene diamine FIGURES 4-5. Method correlation of Gallery analyzer vs. manual DPD-photometric manual methods. Quality control sample recoveries varied from 92 to 106%. The water were refrigerated, and the reagent RC R2 was protected from light. Reagent RC R2 (DPD) indicator to produce a red color in a pH range of 6.2 to 6.5. Absorbance is methods using TRC Low and TRC High applications. samples tested originated from several swimming pools and their concentrations were Immediately after its addition to water, a part of the chlorine reacts with manganese, showed no visible sign of aging (a pink color) during the two weeks of storage. Reagent measured at a wavelength of 510 nm. between 0.11 to 2.89 mg/L, including the spiked samples. Gallery applications are sulfides, or other organic compounds and is unavailable for disinfection. This part is RC R3 was prepared daily. In the total residual chlorine (TRC) method, chlorine liberates iodine from potassium Method Correlation: TRC Low Method Correlation: TRC High designed for concentration areas of 0.1 to 0.5 mg/L (low range) and 0.5 to 3.0 mg/L

called the “chlorine demand of water” as shown in Figure 1. iodide when an excess amount of iodine is present. The liberated iodine reacts with DPD Preliminary tests using frozen reagents showed identical results when compared to 0.7 3.5 (high range). The portion remaining is called “active chlorine” or “total active chlorine.” Part of this refrigerated reagents. 0.6 3.0 to produce a red-colored solution. Absorbance is measured at a wavelength of 510 nm. The FRC method also correlates well with SFS-EN ISO 7393-2:2000 manual methods. total chlorine can react with certain nitrogenous compounds, mostly from sweat and 0.5 , mg/L 2.5 0.02 M KMnO4 Calibrator Stock Solution Tested samples varied in concentration from 0.12 to 2.94 mg/L, including the spiked urine, forming ammonium chlorides. This group of compounds is called “combined Oxidizing agents interfere with the method and these are usually present in very low 0.4 2.0 samples. However the unstable nature of FRC offers a challenge which was concentrations compared to the residual chlorine concentrations. However, sunlight, 0.3 1.5 chlorine” and it is not as effective a disinfectant as the “free chlorine” fraction, which The 0.02 M potassium permanganate (KMnO4) calibrator stock solution is 3547 mg/L as y = 1.034x – 0.014 Results demonstrated in the low concentration area. From the QC sample of 0.1 mg/L, an consists of hypochlorite ions, hypochlorous acid, and chlorine gas. exposure to air, and agitation of the sample may critically effect the outcome. Therefore, equivalent to Chlorine. The solution was prepared from a commercial concentrate. 0.2 r² = 0.986 1.0 y = 1.049x - 0.034 r² = 0.997 82% recovery was also shown with the reference method. Other QC samples showed a quick analysis of the free residual chlorine is essential. Turbidity and color may also 0.1 0.5 Gallery Gallery Results, mg/L A KMnO4 solution is often used in calibrating the residual chlorine method because it is Gallery good recoveries ranging from 92% to 98%. interfere with colorimetric analysis and this can be avoided by application design. A high 0.0 0.0 FIGURE 1. Chemical reactions in water chlorination. concentration of monochloramine can interfere with free chlorine determination. With more stable than an active chlorine solution. The permanganate ion oxidizes the DPD 0.0 0.2 0.4 0.6 0.0 1.0 2.0 3.0 Reference Method, mg/L these samples; the application can be redesigned to avoid this by stopping the reaction molecule in the same way as any active chlorine compound. Reference Method, mg/L References with arsenite or thioacetamide. This solution is stable for up to 12 months if tightly sealed and refrigerated in an amber 1. US EPA, Methods for Chemical Analysis of Water and Wastes, Method 330.5 Equipment bottle in the dark. KMnO4 is light sensitive and degrades over time (especially at low According to these method comparison studies, all TRC methods correlated well with each concentrations). other with no significant systematic error as shown in Figures 4 and 5. The average bias in Chlorine, Total Residual (Spectrophotometric, DPD), 1978: 330 5-1. A Thermo Scientific Gallery, Gallery Plus, or Aquakem™ analyzer can be used. The this evaluation was 2.1 % for the lower concentration area (0.1 to 0.5 mg/L) and 4.9 % for 2. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; method in this paper was performed with the Gallery analyzer measured at a wavelength The calibration may be performed by separate calibrators when the dilution is done the higher concentration area (0.5 to 3.0 mg/L). Baird, R.B.; Eaton, A.D., Eds. 4500-CL (A) Introduction, American Public Health of 510 nm. manually, or by serial calibration when the dilution series is done automatically by the Gallery or Aquakem analyzer. Analysis of low concentration FRC methods in this study was fairly good as shown in Association, 22nd Edition, 2012. Gallery Application Figures 2 and 3. The average bias was -5.4 % for the low range and 0.5 % for the high 3. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; Working KMnO4-solutions Gallery applications are based on EPA 330.5 for the TRC measurement. This method is range. However, some of the individual results deviated significantly, as much as -26 % Baird, R.B.; Eaton, A.D., Eds. 4500-CL (F) DPD Ferrous Titrimetric Method, similar to SFS-EN ISO 7393-2:2000 for both TRC and FRC. Differences in the official A 12 mg/L equivalent Chlorine standard was prepared for High Range calibration from the reference results. This may be due to the nature of the analyte or delays in the American Public Health Association, 22nd Edition, 2012. methods and the Gallery applications are shown in Table 1. (0.5 to 3 mg/L) and a 1.5 mg/L equivalent Chlorine standard for Low Range analysis of samples. Therefore, inserting the FRC samples one at a time or using the (0.1 to 0.5 mg/L) calibration. STAT-Protocol is recommended. 4. Standard Methods for the Examination of Water and Wastewater, Rice, E.W.; Baird, R.B.; Eaton, A.D., Eds. 4500-CL (G) DPD Colorimetric Method, American Table 1. Comparison of residual chlorine methods. Sample Analysis and Sample types During the analysis of free residual chlorine, it was noticed that the highest evaporation (%) Public Health Association, 22nd Edition, 2012. was detected from low concentration samples. Therefore, for future analysis, analyte Samples were taken from several public swimming pools. Sample concentrations were SFS-EN ISO Gallery Chlorine Ref evaporation from the samples should be minimized by using 10 mL test tubes which are 5. Wendelken, S.C.; Losh, D.E.; Fair, P.S. Method 334.0: Determination of Residual EPA 330.5 from 0.12 to 0.58 mg/L for FRC and 0.11 to 0.89 mg/L for TRC. To cover the whole 7393-2:2000 Application (TFS R&D) filled to 1/3 of their full volume. Chlorine in Drinking Water using an On-line Chlorine Analyzer, Version 1.0; concentration range of the calibration (0.1 to 3.0 mg/L), spike samples were prepared. Office of Ground Water and Drinking Water, US EPA: Cincinnati, OH, 2009. potassium potassium iodate + potassium potassium Calibrator Small volumes of potassium hypochlorite solution were added to a series of pool water . permanganate KI permanganate permanganate samples and the concentrations of the spiked samples were analyzed in the method 6. Leasca, S. Peeing in the Pool: So Wrong—and Bad for our Health, Study Says, comparison study. Spiked sample concentrations included 0.12 to 2.94 mg/L for FRC Quality Control Samples March 11, 2014, LA Times, http://www.latimes.com/nation/la/sh/pee-in-the-pool- KI in calibrator, FRC: No KI, no No KI, no no KI, no 20140311-story.html [Online] (Accessed May 5, 2015). Calibration incubation 2 min, incubation incubation, same and 0.11 to 2.89 mg/L for TRC. Each application had low and high quality control (QC) samples. QC samples were incubation, method same calibration for TRC: KI, 1 min calibration for FRC measured by both the Gallery analyzer Residual Chlorine applications and the manual 7. Krans, B. Why peeing in the pool is chemical warfare, March 31, 2104, Healthline calibration for TRC Quality control samples for this study were prepared from sodium hypochlorite solution FRC and TRC (37°C) incubation and TRC spectrophotometric reference method (Chlorine Ref). Results are shown in Table 2. News, http://www.healthline.com/health-news/peeing-in-the-pool-is-chemical- (free chlorine), which was verified the same day by sodium thiosulphate titration. warfare-033114.html [Online] (Accessed May 5, 2015). The intended purpose of chlorination is to kill the microorganisms and bacteria that are Wavelength 515 nm 510 nm 510 nm 510 nm Reference Method Used for the Study harmful to people. However, it may also create some undesired byproducts, such as Table 2. QC sample results with Gallery applications and Chlorine Ref 2. 8. Chloramines- Combined Chlorine Problems, 2011, Pool Wizard, Evaluation of the Residual Chlorine methods was done in the Thermo Fisher Scientific carcinogenic trichloromethane (chloroform), mono-, di- and tri-chloroacetic acids, or KI (%) in reaction http://www.poolwizard.net/problems/chloramines.htm [Online] 1.00 % 1.00 % 0.83 % 0.83 % Finland R&D laboratory using the Gallery discrete analyzer. In this evaluation, a series of trichloramines, and highly toxic cyanogen chloride which are formed when chlorine is mixture Gallery Applications Chlorine Ref (Accessed May 5, 2015). samples were measured against a manual DPD-spectrophotometric method (Chlorine combined with uric acid. Bias Ref) based on EPA 330.5 TRC measurement. The major difference is the EPA method Result, Sample\ Analyte Recovery Bias Result Recovery Bias (Methods) does not measure free chlorine. This manual reference method is similar to SFS-EN ISO Avg. % Combined chlorine in the water of swimming pools is often a symptom of an inadequate In the Gallery TRC applications (TRC Low (0.1 to 0.5 mg/L) and TRC High (0.5 to % mg/L mg/L % mg/L 7393-2:2000 which determines both total and free residual chlorine. A Thermo Scientific mg/L amount of free chlorine. This may cause unwanted effects, such as skin irritation, 3 mg/L)), 6 µL of the phosphate buffer (RC R1) and 6 µl of the DPD indicator reagent Multiskan™ GO Spectrophotometer was used for the manual measurements at a breathing difficulties, and a strong odor. Therefore, it is preferred that the amount of (RC R2) were automatically added to a disposable cuvette. This was followed by an wavelength of 510 nm. QC 0.1 mg/l FRC Low 0.08 82 % -0.02 0.08 82 % -0.02 1 % combined chlorine is as low as possible. automatic addition of 120 µL of sample and potassium iodide solution (RC R3). In the QC 0.5 mg/l FRC Low 0.46 92 % -0.04 0.51 102 % 0.01 -9 % TRC Low application, the sample was introduced first and RC R3 next. In the TRC High To achieve sufficient disinfection and to minimize any undesired byproducts, it is application, this was done in the reverse order. An incubation for 60 seconds at 37°C QC 0.1 mg/l TRC Low 0.09 92 % -0.01 0.09 90 % -0.01 1 % essential to monitor both free and combined residual chlorine concentrations in the water. occurred after the last reaction component was added. Due to the higher temperature Results and Discussion utilized, the incubation time is shorter compared to the standard methods. Finally, QC 0.5 mg/l TRC Low 0.48 97 % -0.02 0.49 99 % -0.01 -2 % Method Comparison Studies Rapid Analysis Using the Gallery Analyzer STAT-Protocol absorbance of the reaction mixture was measured at 510 nm. QC 0.5 mg/l FRC High 0.46 93 % -0.04 0.51 102 % 0.01 -9 % The Gallery analyzer FRC low and high concentration applications were compared to FRC applications (FRC Low an FRC High) are similar to TRC applications, but without QC 1.0 mg/l FRC High 0.97 97 % -0.03 1.01 101 % 0.01 -5 % The unstable nature of residual chlorine in water samples requires a rapid analysis the similar manual spectrophotometric analysis applications and the results are shown the addition of potassium iodide and the incubation step. method. Thermo Scientific™ Gallery™ discrete analyzer offers a STAT-Protocol that below in Figures 2 and 3. QC 2.5 mg/l FRC High 2.46 98 % -0.04 2.68 107 % 0.18 -8 % minimizes the exposure of samples to the atmosphere. In many water laboratories Combined residual chlorine (CRC) applications (CRC Low and CRC High) are QC 1.0 mg/l TRC High 0.98 98 % -0.02 1.05 105 % 0.05 -6 % the discrete analyzer runs non-stop, performing multiple analyses for various types of applications that subtract the FRC results from the TRC results. These calculations FIGURES 2-3. Method correlation of Gallery analyzer vs. manual DPD-photometric QC 2.5 mg/l TRC High 2.65 106 % 0.15 2.70 108 % 0.20 -2 % water samples simultaneously. When analyzing residual chlorine, it is recommended can be automatically performed with the Gallery analyzer. methods using FRC Low and FRC High applications. that the time a sample is in contact with the atmosphere is minimized. When using a Gallery discrete analyzer, a free residual chlorine analysis can be requested using the Contamination from other sample matrixes or reagents was not studied, therefore Both methods showed fairlygood to good recoveries from the QC samples between STAT-Protocol. As a result, the analysis will be performed immediately after inserting analyzing chlorine samples using the STAT-Protocol or by inserting samples one at a Method Correlation: FRC Low Method Correlation: FRC High

0.5 to 2.5 mg/L. Recoveries were from 92 to 98% for FRC and from 97 to 106% the sample into the analyzer. time is recommended. A laboratory can also validate the method for mixed runs. 0.6 3.0 for TRC. The smallest QC (0.1 mg/L) was close to the quantitation limit and showed 2.5 A hypochlorite wash is usually done as part of the discrete analyzer’s daily routine. If this , mg/L This paper compares the Residual Chlorine method used by the Gallery analyzer to the 0.4 recoveries of 82% for FRC and 92% for TRC. Results for the reference method were protocol is used, re-flushing the tubing is recommended. A zero concentration sample 2.0 manual method based on EPA 330.5 and SFS-EN ISO 7393-2:2000. 1.5 82% and 90%, respectively. Low recoveries are thought to be the result of evaporation PO71657-EN 06/15S can also be measured before sample analysis to ensure that all residual analyte is fully 0.2 y = 0.946x – 0.009 y = 1. 005x – 0.025 r² = 0.992 1.0 r² = 0.998 of the analyte. www.thermoscientific.com removed from the instrument. 0.5 0.0 In general, Gallery analyzer applications showed lower results than the reference All©2015 trademarks Thermo are Fisher the Scientifiproperty c ofInc. Thermo All rights Fisher reserved. Scientific ISO andis a trademarkits subsidiaries. of the International Standards Organization. 0.0 All other trademarks are the property of Thermo Fisher Scientifi c and its subsidiaries. This information is presented as an

Gallery Results, mg/L 0.0 0.2 0.4 0.6 Gallery Results Gallery 0.0 1.0 2.0 3.0 method, Chlorine Ref. This information is not intended to encourage use of these products in any manners that might infringe the Thermo Fisher Scientifi c, Reference Method, mg/L example of the capabilities of Thermo Fisher Scientifi c products. It is not intended to encourage use of these products in any intellectual property rights of others. Sunnyvale, CA USA is Reference Method, mg/L manners that might infringe the intellectual property rights of others. Specifi cations, terms and pricing are subject to change. ISO 9001Certifi ed. Not all products are available in all countries. Please consult your local sales representative for details.

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