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Lc-Ms/Ms Analysis of Acidic Herbicides in Water Using Direct Injection

LC-MS/MS ANALYSIS OF ACIDIC IN WATER USING DIRECT INJECTION

Authors: Renata Jandova, Euan Ross, Simon Hird, Marijn Van Hulle Waters Corporation, Stamford Av., Altrincham Road, SK9 4AX Wilmslow UK

INTRODUCTION The presence of pesticides in surface and ground waters is of concern globally because of the impact on aquatic ecology but also the potential to contaminate drinking water supplies. Presence of pesticides in European waters is regulated through different directives. The Drinking Water Directive1 sets a maximum limit of 0.1 μg/l for individual pesticide residues present in a sample (0.5 μg/l for total pesticides). The Water Framework Directive (WFD)2 deals with surface waters, coastal waters, and groundwater. Member States must identify River Basin Specific Pollutants and set their own national environmental quality standards (EQS) for these substances (e.g. 2,4-D: 0.1 µg/l in France and Germany). In the USA, drinking water is regulated under the Safe Drinking Water Act.3 Through this regulation, EPA established National Primary Drinking Water Regulations (NPDWRs) that set mandatory Maximum Contaminant Levels (MCL) for drinking water (e.g. 2,4-D: 70 µg/l). Some states have set guidance values at lower concentrations (e.g. 2,4-D: 30 µg/l in Minnosota). Surface and ground waters are regulated under the Clean Water Act4, which establishes Water Quality Standards (WQS) but these don’t include any acidic herbicides. Although regulations vary from country to country, many look to guidelines established by EU, USA or the WHO.5 Therefore, there is a need for reliable analytical methods for monitoring acidic herbicides in various types of water. This work describes a rapid and sensitive method for the determination of 20 acidic herbicides in a variety of different types of water sample, with minimal sample preparation. The method is suitable for checking compliance with regulatory limits in many parts of the world. METHODS Aliquots of surface water samples (10 ml) were centrifuged and passed through syringe PVDF filter (0.2 µm). Aliquots (1.5 ml) from each water sample were then transferred to deactivated glass vials and acidified (30 µl of 5 % formic acid) prior to analysis. The accuracy (trueness and precision) of the method was assessed by analysis of water samples. Two different samples of drinking and surface waters, previously shown to be blank, were spiked with the compounds of interest at 0.02 and 0.1 µg/l three times; n=6 for each water type at each concentration.

UPLC conditions and gradient Compound RT (min) Polarity MRM Cone (V) CE (eV) Compound RT (min) Polarity MRM Cone (V) CE (eV) MS parameters Clopyralid 2.91 ESI+ 192 > 110 30 30 Ioxynil 7.29 ESI- 370 > 127 30 32 Parameter Setting Parameter Setting 192 > 146 30 20 370 > 215 30 30 UPLC System ACQUITY UPLC® I-Class 4.19 ESI+ 262 > 149 30 25 7.66 ESI- 233 > 161 30 13 MS instrument Xevo® TQ-XS Column HSS T3 column (1.8µm, 2.1×150 mm) 262 > 202 30 22 233 > 125 30 25 Source Electrospray 5.45 ESI- 175 > 145 20 5 7.49 ESI- 256 > 198 20 12 Column Temp. 40 °C 219 > 175 20 5 254 > 196 20 12 Polarity ESI-/ESI+ switching Mobile phase A 0.02 % formic acid (aq.) 5.79 ESI- 253 > 233 30 8 7.74 ESI+ 328 > 282 30 16 Capillary voltage 1 kV ESI-/ 2kV ESI+ Mobile phase B Methanol (LC-MS grade) 253 > 175 30 22 328 > 254 30 25 Desolvation temperature 300 °C Bentazone 5.99 ESI- 239 > 132 30 25 7.76 ESI- 213 > 141 30 10 Flow rate 0.4 mL/min 239 > 175 30 20 213 > 71 30 15 Desolvation gas flow 1000 L/Hr Injection volume 250 µL Bromacil 6.17 ESI- 259 > 203 30 18 2,4,5-T 7.77 ESI- 253 > 195 30 15 Source temperature 120 °C 259 > 160 30 18 253 > 159 30 25 Time (min) %A %B Imazaquin 6.31 ESI+ 312 > 267 30 20 2,4-DB 8.13 ESI- 161 > 125 30 10 Cone gas flow 150 L/Hr Initial 80 20 312 > 199 30 25 247 > 161 30 15 2,4-D 6.92 ESI- 219 > 161 30 13 MCPB 8.17 ESI- 227 > 141 20 15 9 0 100 219 > 125 30 25 229 > 163 20 15 12 0 100 MCPA 7.12 ESI- 199 > 141 30 13 8.37 ESI- 267 > 195 30 15 201 > 143 30 13 269 > 197 30 15 15 80 20 Haloxyfop 8.64 ESI+ 362 > 288 30 25 362 > 272 30 32

RESULTS AND DISCUSSION Quantification and Accuracy: 6.31 100 Standard solutions, prepared in drinking and surface water at seven concentrations (0.01, 0.02, 0.05, 0.10, 0.20, 0.50 and 1.0 µg/L), were used for bracketed calibration. In all cases, the correlation coefficients (r2) were >0.99 with residuals of <20% The accuracy and precision of the method was determined from the analysis of spiked water samples. Trueness was found to be within the range 88 to 120%. Repeatability was good with RSDs ≤7% at 0.1 µg/L and ≤20% at 0.02 µg/L (n = 6 per each level). Figure 3 shows the results in detail.

7.74 Drinking water

5.99 %

7.66 4.19 7.49

7.29 8.37 7.76 8.64 Surface water

7.12 7.77 2.91 6.92 8.17 6.17 8.13 5.45 5.79 0 Time 2.50 3.00 3.50 4.00 4.50 5.00 5.50 6.00 6.50 7.00 7.50 8.00 8.50 Figure 1: 20 acidic herbicides with their retention times (overlay of two MRM transitions). Standard prepared in drinking water at 0.1 µg/L. Sensitivity and selectivity of the method: Excellent sensitivity and selectivity was demonstrated by the response for each compound detected from Figure 3: Trueness (%) and precision (% RSD) from measurements of the analysis of drinking and surface water spiked at 0.02 µg/L, which is well below the maximum limits. spiked water samples (n = 6 per each concentration). Figure 2 shows representative example of two MRM chromatograms for drinking and surface water. Laboratories are expected to provide methods with lower limits of quantification (LLOQ) of at least one Fragile compounds and soft ionization: third of the EQS. The sensitivity observed suggests that detection and quantification of all compounds at 2,4-DB, dicamba, MCPB and triclopyr, exhibited fragmentation within the source region under typical settings. lower concentrations should be possible. Therefore, the temperature of the source block and the desolvation gas was reduced to 120 °C and 300 °C, respectively, which increased the response of the deprotonated molecular ion. These compounds were also 2,4-D 2,4-D acquired in Soft Ionization mode, a function enabled in the MS acquisition file that applies a shallower gradient of 100 A) 100 B) voltages to the StepWave XS™ ion transfer optics to reduce fragmentation during transmission of ions to the first % % 219 > 161 219 > 161 quadrupole. Reducing fragmentation can result in significant improvements in sensitivity as shown in Figure 4. 0 min 0 min

180000 100 100 160000 Normal mode % 219 > 125 % 219 > 125 140000 Soft ionization mode 0 min 0 min [M-H]- 256 > 198 120000

Clopyralid Clopyralid 100000 - 100 100 [M-H] 227 > 141 80000 % 192 > 110 % 192 > 110 60000 - 0 min 0 min [M-H] 219 > 175 40000

- 100 100 20000 [M-H] 247 > 161

% 192 > 146 % 192 > 146 0

0 min 0 min Dicamba MCPB 2,4-DB Triclopyr

Dicamba Dicamba 100 100 100 StepWave XS™ Soft ionization mode % 175 > 145 % 175 > 145

0 min 0 min % 100 100 219 > 175 219 > 175 % % Normal mode 0 min 0 min 3.00 3.50 4.00 4.50 5.00 5.50 6.00 6.50 7.00 3.00 3.50 4.00 4.50 5.00 5.50 6.00 6.50 7.00

0 Time Figure 2: Monitored MRM transitions of selected herbicides in matrix matched standard at 0.02 µg/l 6.00 6.10 6.20 6.30 6.40 6.50 6.60 6.70 in A) drinking water and B) surface water. Quantitative transition is on the top. Figure 4: Enhanced signal for molecular ion of fragile herbicides achieved with Soft Ionization mode to control the StepWave XS™

References CONCLUSION 1. European Commission (1998). Council Directive 98/83/EC of 3  A method for determination of 20 acidic herbicides, in drinking and surface water, using LC-MS/MS, has been November 1998 on the quality of water intended for human consumption. Off. J. Eur. Communities 1998. developed, which is suitable for monitoring waters for compliance with regulatory limits. 2. European Commission (2000). Directive 2000/60/EC of 23 October 2000 establishing a framework for community action in the field of water  This method uses direct injection with no sample preparation so avoids the time, costs and potential losses associated policy as last amended by Commission Directive 2014/101/EU (OJ No L with techniques such as liquid-liquid extraction (LLE) solid-phase extraction (SPE). 311, 31.10.2014, p32). 3. https://www.epa.gov/sdwa. "Safe Drinking Water Act (SDWA)." United  Reducing the temperature in the source and using Soft Ionization mode to optimize StepWave XS™ parameters, States Environmental Protection Agency. Accessed 05 April 201 4. https://www.epa.gov/laws-regulations/summary-clean-water-act. provided significant increases in response for the more “fragile” compounds in the suite of analytes. "Summary of the Clean Water Act, 33 U.S.C. §1251 et seq. (1972)." United States Environmental Protection Agency. Accessed 05 April  In-house validation showed very good linearity and residuals over the concentration range studied and accuracy of the 2018. method was observed to be excellent. 5. World health organisation (2017). Guidelines for drinking-water quality: fourth edition incorporating the first addendum. Geneva. Licence: CC BY -NC-SA 3.0 IGO. TO DOWNLOAD A COPY OF THIS POSTER, VISIT WWW.WATERS.COM/POSTERS ©2018 Waters Corporation

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