ANALYTICAL SCIENCES JULY 2018, VOL. 34 831 2018 © The Japan Society for Analytical Chemistry

Determination of in Grape and Apricot Samples Using High-resolution Continuum Source Electrothermal Molecular Absorption Spectrometry

· Yasin ARSLAN,* J. A. C. BROEKAERT,** and Ibrahim KULA***†

*Department of Nanoscience and Nanotechnology, Faculty of Arts and Science, Mehmet Akif Ersoy University, 15100, Burdur, Turkey **Institute of Inorganic and Applied Chemistry, University of Hamburg, Hamburg, Germany ***Department of Chemistry, Faculty of Science, Mug˘la Sıtkı Koçman University, 48000, Mug˘la, Turkey

The determination of sulfur in apricot and grape samples was performed by using high-resolution continuum source electrothermal molecular absorption spectrometry based on vaporization of the monosulfide (CS) . CS forms in the gas phase without the addition of any molecule-forming element, since graphite cuvette contains plenty of carbon as well as food samples. A mixture of 15 μg Pd + 10 μg Mg was used in solution as the chemical modifier. The best sensitivity was obtained at 900°C of the pyrolysis temperature with a K2SO4 calibration solution. The calibration plot drew a linear path between 50 and 1600 ng of sulfur, and the limit of detection was found to be 23 ng. The accuracy of the method was confirmed with the use of a standard reference material (Rice Flour, NIST SRM 1568a). The sulfur content in chemically dried apricot samples (1987 ± 45 mg/kg) was determined to be higher than that of apricot samples dried under sunshine.

Keywords Sulfur, molecular absorption spectrometry, inductively coupled plasma optic emission spectrometry, electrothermal vaporization

(Received December 7, 2017; Accepted March 8, 2018; Published July 10, 2018)

indispensable for many fields, and that they are also found Introduction naturally in different organic phases at trace levels, their sensitive determination has gained utmost importance. Sulfur is naturally found in the earth and it is a significant In order to determine the concentrations of sulfur and its essential element for living creatures, since various proteins and compounds in the real samples, various analytical detection enzymes include sulfur and/or its compounds.1 On the other techniques have been employed, such as the gravimetric,10,11 12 hand, some sulfur compounds, such as SO2, are highly toxic and UV-Vis spectrometry, inductively coupled plasma–optical cause respiratory diseases, acid rain, and layer depletion.2,3 emission spectrometry (ICP-OES),13,14 inductively coupled 15–17 According to World Health Organization (WHO), SO2 blocks plasma–mass spectrometry (ICP-MS), gas chromatography specific nerve signals, reduces lung performance and creates (GC),18,19 X-ray fluorescence (XRF),20,21 and laser-induced 4,5 22 allergen effects. However, SO2 has been widely used to breakdown spectrometry. Each technique has different prevent the growth of microorganisms due to its antioxidant and drawbacks, such as high cost, time consumption, and poor antimicrobial properties. It has also been used to protect the precision, accuracy and selectivity. None of them is free from color and flavor of dried fruits, such as apricot, apples, plums interferences. Molecular absorption spectrometry (MAS) with etc.6–8 Furthermore, sulfur compounds are also exploited in continuum source has been widely used to determine non- different fields, such as fertilizer, alloying agent, disintegration metals, such as sulfur and the halogens, since the 1970s. On the agent and car batteries.9 There are some limitations for the other hand, a high-resolution continuum source MAS technique sulfur amount consumed in different application areas. For was started to be used for the determination of non-metals since example, according to CODEX General Standard for Food 2000s23 owing to its simplicity, lower analysis cost, more Additives (CODEX STAN 192-1995), the maximum sulfur rapidness, precision and accuracy properties.1 amount in dried apricot and raisin samples should be 2000 and Gunduz and Akman4 used a solid sampling high-resolution 1500 mg/kg, respectively. Furthermore, European Directive continuum source electrothermal atomic absorption spectrometry 95/2/EC (1995) on food additives reported that the maximum (SS HR-CS ETAAS) to determine sulfur at 258.056 nm in 6 SO2 on dried fruit samples should not exceed 2000 mg/kg. spinach, leek, lettuce, radish, Brussels sprouts, zucchini and Because of the fact that sulfur and/or its compounds are chard samples. In this study, a Pd/citric acid mixture was used as a chemical modifier. The optimum pyrolysis and evaporation † To whom correspondence should be addressed. temperatures for CS were found to be 1000 and E-mail: [email protected] 2400°C, respectively. The accuracy of this method was tested 832 ANALYTICAL SCIENCES JULY 2018, VOL. 34 using different vegetal certified reference materials, and the Table 1 Operating conditions for apricot and grape samples in results were found in good agreement with certified values. The the microwave digestion system limit of detection (LOD) and characteristic mass were found to Step Temperature/°C Time/min Power/W be 7.5 and 8.7 ng, respectively. In another study,6 sulfur was determined at both 257.959 and 1 50 2 250 258.056 nm in some nuts and dried-fruits samples by using a 2 50 6 250 HR-CS ETAAS. Thiourea was used as calibration standard for 3 170 5 400 sulfur. The mixture of Pd/citric acid was used as a chemical 4 210 8 600 modifier. The optimum pyrolysis and vaporization temperatures were found to be 800 and 2200°C, respectively. The certified reference spinach, milk powder and tea samples were used to check the accuracy of the method. The LOD was found to be Experimental 21.6 ng S using the optimum experimental conditions. Camera et al.24 reported a method for S determination at Instrumentation 258.0330 nm based on a carbon monosulfide (CS) molecule in HR-CS-ETMAS (ContrAA 700 Analytik Jena, Germany) petroleum green coke samples by HR-CS MAS. The equipped with a 300-W xenon short-arc lamp (XBO 301, GLE, experimental conditions were tested to obtain better accuracy, Berlin, Germany) was used for all of the measurements. precision, linearity, limits of detection and quantification, (99.99%) was used as a purge gas. Pyrolytic graphite tubes sensitivity, selectivity, robustness, and measurement uncertainty were employed for S determination among all experimental values. The optimum pyrolysis and vaporization temperatures studies. The absorbance of CS molecules obtained by three were found to be 1000 and 2600°C, respectively. Using the pixels was measured at 257.958 nm. A microwave-oven optimum conditions, the sulfur contents of samples were found digestion system (Cem, Mars 5 Model) was used to digest the to be between 6.20 and 9.40 mg/g. Furthermore, the limit of grape and apricot samples and the standard reference material detection (LOD) and the quantitation (LOQ) values were (Rice Flour, NIST SRM 1568a). calculated by the Weighted Least-Squares (WLS) method. Özbek and Baysal25 applied HR-CS ETAAS to determine Standards, reagents and samples sulfur at 258.056 nm in hair samples of autistic and age-match All of the reagents used were of analytical grade. Furthermore, control group children. Firstly, hair samples were digested by a acids were purified by sub-boiling distillation in a quartz microwave digestion method, and then extraction with HCI apparatus. An 18 MΩ cm–1 deionized -purification system hydroxylation was carried out for the determination of the total (Millipore, Bedford, MA, USA) was used in all experiments. protein and albumin based on the incubation condition at 110°C. The stock aqueous solution of sulfur (1000 mg/L) was prepared The accuracy of this method was confirmed with the use of a by dissolving thiourea, sodium sulfate and potassium sulfate standard reference material (hair, NCS ZC 81002b) based on supplied from Merck in deionized water. A working solution of molecule formation curves of CS. Additionally, the relevance of sulfur was also prepared from the above-mentioned stock the sulfur levels of autistic children’s hairs with their total solution by necessary dilution. protein and albumin levels were also investigated. Three apricot samples (yellow apricot sample-chemically Huber et al.26 performed a study for sulfur determination in dried; brown apricot sample-chemically dried; and apricot diesel fuel samples using HR-CS ETAAS. A mixture of Pd and sample-dried under sun shine) were supplied from Malatya, Mg was used as a chemical modifier, and L-cysteine was used as Turkey. This province leads apricot production, and exports a sulfur standard. The method was applied for four diesel apricots worldwide. One grape sample chemically dried was samples, such as two S10 and two S500 samples. The accuracy supplied from Manisa, Turkey. Manisa is the second-biggest of the method was confirmed with the use of a certified reference grape producer city worldwide. The samples were exposed to

S material (diesel fuel, NIST 2724b) after diluting with propan- SO2 gas for drying. SO2 gas was obtained by the burning of 1-ol. The characteristic mass, LOD and LOQ values were found elemental sulfur. to be 17 ± 3 ng, 1.4 mg/kg and 4.7 mg/kg, respectively. Pd(NO3)2 (Sigma-Aldrich), Mg(NO3)2 (Merck, Germany), The aim of this study was to evaluate the sulfur content via Ca(NO3)2 (Riedel-de-Haen, Switzerland), (NH4)3PO4 (Merck, carbon mono sulfide molecular absorption in apricot samples Germany) and, Pd(NO3)2 + Mg(NO3)2, prepared in HNO3, were dried both chemically and under sunshine and grape samples investigated at 5% (v/v) concentration to determine the best dried chemically. A S determination at 257.958 nm in apricot modifier. samples (yellow apricot-chemically dried, brown apricot- chemically dried and apricot-dried under sun shine) and Procedure chemically dried grape samples was done by using HR-CS- Supplied samples were cut into small pieces and then dried at ETMAS based on the vaporization of CS molecules. Various 130°C in an air-ventilated oven for 3 h. Afterwards, all samples analytical parameters, such as chemical modifiers, calibration were cooled and crushed in a ceramic mortar and stored in solutions, pyrolysis, evaporation temperatures and absorption tightly closed folding polyethylene cups. The 0.250 g for each lines for CS molecules, were optimized to obtain better accuracy, sample was separately placed into a teflon container, and then precision, linearity, LOD, LOQ, sensitivity and selectivity. The 3 mL of concentrated HNO3 (Suprapure, Merck) and 0.5 mL of sulfur amounts in the samples were determined by both the HR- concentrated H2O2 (Suprapure, Merck) were added. The CS-ETMAS and ICP-OES techniques. Additionally, scanning container was sealed tightly, and then positioned in the carousel electron microscopy (SEM) with energy-dispersive X-ray of a microwave oven. The digestion program is given in Table 1. fluorescence spectrometry (EDX) images of both the surface The standard reference material (Rice Flour, NIST SRM 1568a) shell and inner regions of yellow apricot, brown apricot and was also digested by a microwave oven digestion system that grape samples were obtained to investigate the accumulation employed the same program. After the cooling process region of sulfur into the samples. terminated, dissolved samples were transported to a 50-mL flask and filled by 18 MΩ cm–1 deionized water up to 50 mL. ANALYTICAL SCIENCES JULY 2018, VOL. 34 833

Table 2 Temperature program for the determination of sulfur via CS molecule with potassium sulfate as calibration solution

Stage T/°C Ramp/°C s–1 Hold time/s Ar flow rate/L min–1

Drying 110 5 15 2.0 Pyrolysis 900 50 10 2.0 Auto-zero 900 — 5 0 Evaporation 2500 1000 5 0 Cleaning 2650 1000 5 2.0

Then, 50 μL portions of the samples were put onto the graphite cuvette, into which 15 μL (15 μg) from a 1000 μg/mL of Pd(NO3)2 standard solution and 10 μL (10 μg) from a 1000 μg/mL of Mg(NO3)2 standard solution were injected onto the sample as chemical modifiers. The sulfur amounts in the samples were determined by HR-CS-ETMAS. The calibration plot was drawn so as to be linear between 50 and 1600 ng of sulfur (N = 3). Fig. 1 Effect of different chemical modifiers on the CS signal Because of the higher sulfur content of yellow apricot sample- (257.958 nm wavelength). chemically dried, this sample was diluted 5 times with deionized water after the digestion procedure. Thus, all samples could be analyzed in the working range of the calibration plot. Under the optimum experimental conditions, potassium sulfate the volatilization process can be carried out without any was selected as the most appropriate working solution for sulfur, interferences. During the experiment, the amount of excess based on the better accuracy, precision, LOD, LOQ and working reagent/modifier may be put into the sample and/or atomizer so range. The temperature program for potassium sulfate is shown that the analyte was transferred into less-volatile compounds in Table 2. and/or the matrix was transferred into more-volatile compounds. In addition, a modification may also provide an interactive relation between the sample and the graphite surface.29 Results and Discussion In this study, different chemical modifiers of 40 μg of Pd, Mg, Ca and phosphate absolute were investigated for both alone and Wavelength selection for carbon monosulfide their combination prepared from 1000 μg/mL standard solutions The method was based on the formation of of Pd(NO3)2, Mg(NO3)2, Ca(NO3)2, and (NH4)3PO4, respectively. monosulfide molecules in the gas phase. The measurement of The preliminary results showed that the sensitivity was increased absorption was done for one of its finely structural rotational when a standard solution of thiourea including 800 ng sulfur lines. The amount of CS molecule and sulfur in the samples was used in combination with these modifiers. As shown in was observed to be proportional to each other. There were Fig. 1, the optimum modifier amounts were found as a several absorption lines, which were reported to be the most combination with 15 μg of Pd prepared from Pd(NO3)2 and sensitive lines (257.593; 257.958; 258.056) for sulfur 10 μg of Mg prepared from Mg(NO3)2, respectively. Matrix determination.27 Dittrich et al.28 determined sulfur at 469.413 nm modification was shown to have great importance for graphite using the normal atmospheric argon-a microwave-induced furnace studies. Optimization of the chemical modifier was plasma method, and at 383.73 nm (S2 molecular band) using a repeated with sodium sulfate and potassium sulfate as working glow discharge in the furnace nonthermal excitation solutions for sulfur. The best CS molecular absorption signals spectrometry/molecular nonthermal excitation spectrometry were received by using the same modifier. + method based on the emissions of S atoms, S ions, S2 and CS molecules using sulfate. Pyrolysis and evaporation temperatures In this study, the CS signal was obtained in all of the above Two important parameters, which are pyrolysis and evaporation wavelengths, except for 469.413 and 383.73 nm. The most temperatures for CS molecules, play a significant role for the sensitive signal was obtained at the lines of both 258.056 and MAS method to determine sulfur because of elimination of the 257.958 nm. The wavelength at 258.056 nm was not used sample matrix.30 because of the fact that a potential overlap was reported with the Several heating stages should be optimized in the graphite Fe lines.27 Therefore, 257.958 nm was applied in the all apricot furnace method to dry the sample, to remove the sample matrix and grape samples. (pyrolysis) and to volatilize the analyte atoms. The cleaning stage is also an important optimization stage for this method to Selection of chemical modifier remove any residual material for further analysis. Therefore, In general, the chemical modifier may attract sulfur and permit the optimizations of pyrolysis and evaporation temperatures a more sufficient stabilization of the sulfur species until it is should be performed to obtain better sensitivity and more released under graphite furnace conditions. This situation accurate results. Several compounds containing sulfur, such as improved the formation efficiency of CS molecules. Otherwise, thiourea, Na2SO4 and K2SO4, were investigated to find the best sulfur species in direct contact with the graphite surface may be working solution, in which the sulfur concentration was 800 ng, trapped in its porous (layered) structure, and turn into the more and the combination of 15 μg of Pd and 10 μg of Mg was used volatile forms instead of CS molecules.27 The purpose of the as a chemical modifier. The best sensitivity was obtained at a modifiers was to encourage the intended chemical reaction to 900°C pyrolysis temperature with a K2SO4 calibration solution increase the separation of the matrix and analyte. Consequently, (Fig. 2). At the pyrolysis stage, the decomposition of sample 834 ANALYTICAL SCIENCES JULY 2018, VOL. 34

Table 3 Results (mg kg–1) obtained for the determination of sulfur via CS molecule in samples by HR-CS-ETMAS and ICP- OES (calibration with potassium sulfate standard, N = 3)

HR-CS-ETMAS/ ICP-OES/ Sample S mg kg–1 S mg kg–1

Yellow apricot-chemically dried 1987 ± 45 2000 ± 23 Brown apricot-chemically dried 200 ± 10 208 ± 17 Apricot-dried under the sun shine

Table 4 SEM-EDX results for all samples Fig. 2 Pyrolysis curves obtained 800 ng of sulfur introduced in Sample Element Weigh, % Atomic, % several compounds containing sulfur when monitoring the 257.958 nm CS molecular line in the presence of 15 μg Pd + 10 μg Mg modifier. Yellow apricot in shell O K 94.56 97.65 S K 0.29 0.15 Cl K 0.55 0.26 K K 4.60 1.94

Yellow apricot in inner region O K 93.34 97.17 K K 6.66 2.83 Brown apricot in shell O K 92.13 96.54 P K 0.76 0.41 K K 7.10 3.04 Brown apricot in inner region O K 93.11 96.99 P K 0.66 0.35 K K 6.23 2.66 Grape sample in shell O K 80.68 92.49 Si K 1.57 1.02 S K 2.06 1.18 K K 3.02 1.42 Ca K 0.80 0.37 Ti K 1.09 0.42 Cu L 10.77 3.11 Fig. 3 Evaporation curves obtained 800 ng of sulfur introduced in Grape samples in inner region O K 97.66 99.03 several compounds containing sulfur when monitoring the 257.958 nm K K 2.34 0.97 CS molecular line in the presence of 15 μg Pd + 10 μg Mg modifier.

Analytical results matrix to gaseous products occurs. Pyrolysis curves drew a The 4 food samples, which were 3 dried apricots samples and plateau shape in some cases. Leaping of the signal can also be 1 dried grape sample, were analyzed using HR-CS-ETMAS. seen.27 This difference was attributed to the temperature The sulfur amount in these samples were determined by ICP- required for destruction of the sample matrix. When the OES for comparing the two methods. The experimental results pyrolysis temperature change interval was narrow, a sudden rise were found to be in good agreement with both methods based in the CS signal was observed. Additionally, inorganic species on t-test calculations for the sulfur concentration at a 95% are less volatile: the boiling points of potassium sulfate and confidence level, as shown in Table 3. When fresh apricot was sodium sulfate are 1689 and 1429°C, respectively. On the other dried, about a 74.7% of weight loss was detected. Therefore, hand, thiourea decomposes at 182°C. As shown in Fig. 2, the the sulfur concentration in dried samples should be divided by sensitivity was higher with inorganic species. This standard was 4. For example, as the sulfur concentration in the dried yellow chosen for the working solution for sulfur in further studies. apricot sample was found to be just about 2000 mg/kg, it was The evaporation temperature for CS molecules has also been about 500 mg/kg in the fresh apricot sample for an estimation. optimized with the same working solution and conditions. Broad transient signals were obtained at lower evaporation SEM-EDX results temperatures, while signals were sharper and higher (less A scanning electron microscope (SEM) was used to observe tailing) at higher evaporation temperatures. The best sensitivity both the surface shell and the inner region of the yellow apricot, and linearity was obtained at a 2500°C evaporation temperature brown apricot and grape samples. In addition to SEM, energy- with K2SO4, as shown in Fig. 3. The sensitivity was not good in dispersive X-ray fluorescence spectrometry (EDX) was also the case of using thiourea for the working solution because of used to observe the accumulation of sulfur in the samples. Two the fact that it was more volatile and decomposed at lower measurements were performed from the surface shell and the temperatures. After using 2200°C for the evaporation inner region for all samples (Table 4). Sulfur was observed in temperature, a more broad and tailing signal was obtained with the surface of the shell for yellow apricot and grape samples. thiourea. But, the signal was not observed in a brown apricot sample in both the surface of the shell and the inner region because of the fact that the sulfur amount for brown apricot was lower than that ANALYTICAL SCIENCES JULY 2018, VOL. 34 835

Fig. 4 Result of SEM-EDX for yellow apricot. A, In shell; B, inner region. Fig. 6 Result of SEM-EDX for grape. A, In shell; B, inner region.

Table 5 Results obtained for the determination of sulfur in standard reference material via carbon mono sulfide molecular absorption using HR-CS-ETMAS with Pd + Mg modifier

Certified value, Found valuea, Standard reference material % (m/m) % (m/m)

NIST SRM 1568a Rice Flour 0.120 ± 0.002 0.117 ± 0.002

Calibration with potassium sulfate; pyrolysis temperature 900°C, evaporation temperature 2500°C; all values in (m/m) % (N = 5). a. All results expressed as mean and confidence interval at 95% level.

five replicates, and were compared to the certified value. The values obtained for the standard reference material was consistent with the certificate values at a 95% of the confidence level.

Figures of merit The linear range was found between 50 and 1600 ng of sulfur in HR-CS-ETMAS with a potassium sulfate working solution. The determination of sulfur was carried out at a wavelength of 257.958 nm with correlation coefficients ≥0.999. The LOD (3s, Fig. 5 Result of SEM-EDX for brown apricot. A, In shell; B, inner N = 13) and LOQ (10s, N = 13) were found to be 23 and 50 ng region. with the blank measurements, respectively. The analytical performance of the method is comparable with other methods reported in the literature review, as shown in Table 6. of yellow apricot and grape samples. The sulfur was not found in the inner region of yellow, brown and grape samples, as shown in Table 4. This result revealed that the sulfur was not Conclusions diffused to the inner region of the samples. SEM images and EDX analyses are given in Figs. 4 – 6 for the shells and inner The developed method for the determination of sulfur via CS regions of yellow apricot, brown apricot and grape, respectively. molecules by HR-CS-ETMAS was successfully performed in all food samples. Additionally, this method was very simple Analysis of standard reference material and accurate for sulfur determination in grape and apricot The accuracy of method was confirmed by the determination samples. The pyrolysis and volatilization temperatures were of sulfur via carbon monosulfide molecules in the standard optimized, and found to be 900 and 2500°C. In turn, the limit reference material (Rice Flour, NIST SRM 1568a) by using HR- of detection was found to be 23 ng. The experimental findings CS-ETMAS (Table 5). The measurements involved the mean of revealed that the sulfur amount in any samples can be easily 836 ANALYTICAL SCIENCES JULY 2018, VOL. 34

Table 6 Comparison of analytical figures of merit for the reported and literature methods Pyrolysis LOD Sample matrix Method Linear range for S Reference temperature/°C

0.01% Coal HR-CS-FAAS 0.005 – 20% — 1 5.8 ng Crude oil HR-CS-GFMAS 15 – 1000 ng 600 2 7.5 ng Various vegetables SS-HR-CS-ETAAS 7.5 – 1500 ng 1000 4 21.6 ng Some nuts and dried foods HR-CS-ETAAS 21.6 – 2500 ng 800 6 3.0 ng Solid samples HR-CS-ETAAS 50 – 2500 ng 1000 27 3.5 ng Onion and garlic SS-HR-CS-ETAAS 0.01 – 10 µg 1000 31 0.03 mg/g Food materials HR-CS-FAAS — — 33 23 ng Apricot and grape HR-CS-ETMAS 50 – 1600 ng 900 This study

detected using this method. The sulfur amount in the chemically 1991, 74, 745. dried samples (yellow apricot, brown apricot and grape samples) 9. G. Baumbach, T. Limburg, and J. W. Einax, Microchem. J., were higher than that of dried under sunlight (brown apricot 2013, 106, 295. sample). The optimized method was confirmed with the use of 10. D. K. A. Padma, Talanta, 1986, 33, 550. the standard reference material (Rice Flour, NIST SRM 1568a) 11. G. A. Norton and R. E. Peters, Fuel, 1993, 72, 1573. at the 95% confidence level. In order to compare the results, the 12. S. S. M. Hassan, M. S. A. Hamza, and A. H. K. Mohamed, samples were also analyzed by ICP-OES. The results were in Anal. Chim. Acta, 2006, 570, 232. good agreement based on t-test calculations at the 95% 13. R. E. Santelli, E. P. Oliveira, M. F. B. Carvalho, M. A. confidence level. The HR-CS-ETMAS was an alternative Bezerra, and A. S. Freire, Spectrochim. Acta, Part B, 2008, method to determine the sulfur concentration in complex 63, 800. matrices, and was a quite challenging instrument that provides a 14. L. Ackerman, J. Rohovec, and O. Šebek, Geostand. bandwidth below 1.6 pm per pixel.31 For this reason, it was Geoanal. Res., 2012, 36, 407. possible to measure spectral interference at a very narrow 15. M. E. Erdman, C. A. Lee, W. Yang, and L. Ingram, wavelength (several picometers) that overlaps with the analytical Geostand. Geoanal. Res., 2013, 38, 51. line of the molecule.31,32 Finally, the determinations of sulfur in 16. R. S. Amais, S. E. Long, J. A. Nóbrega, and S. J. apricot and grape samples were performed successfully by using Christopher, Anal. Chim. Acta, 2014, 806, 91. HR-CS-ETMAS. 17. W. P. O. Filho, D. L. G. Borges, T. D. Saint’Pierre, M. Dupim, F. Vale, B. Marques, and F. R. Medeiros, Fuel, 2017, 202, 227. · Acknowledgements 18. I. Al-Zahrani, C. Basheer, and T. Htun, J. Chromatogr. A, 2014, 1330, 97. The authors wish to thank financial support of the foundation of 19. K. H. McKelvie and K. B. Thurbide, Anal. Methods, 2017, The Council of Higher Education of Turkey (No. 2547/39). 9, 1097. This study was funded by No. 2547/39 20. Y. Kim, J. Lee, H. Yoon, and N. Woo, Microchem. J., 2016, 124, 594. 21. V. Chubarov, T. Aisueva, and A. Finkelshtein, Anal. Lett., Conflict of Interest 2016, 49, 2099. 22. S. Musazzi, E. Golinelli, U. Perini, F. Barberis, and G. A. All authors declare that they have no conflict of interest. This Zanetta, SAS, IEEE, 2012, 1. work did not contain any studies with human participants or 23. D. J. Butcher, Anal. Chim. Acta, 2013, 804, 1. animals performed by any of the authors. 24. A. S. Camera, P. P. Arcênio, W. O. P. Filho, T. A. Maranhão, F. J. S. Oliveira, and V. L. A Frescura, Microchem. J., 2017, 134, 301. References 25. N. Ozbek and A. Baysal, Spectrochim Acta, Part B, 2017, 130, 17. 1. A. Baysal and S. Akman, Talanta, 2011, 85, 2662. 26. C. S. Huber, M. G. R. Vale, B. Welz, J. B. Andrade, and M. 2. H. R. Cadorim, È. R. Pereira, E. Carasek, B. Welz, and J. B. Dessuy, Spectrochim Acta, Part B, 2015, 108, 68. B. Andrade, Talanta, 2016, 146, 203. 27. M. Resano and M. R. Florez, J. Anal. At. Spectrom., 2012, 3. B. Welz, F. G. Lepri, R. G. O. Araujo, S. L. C. Ferreira, M. 27, 401. D. Huang, M. Okruss, and H. Becker Ross, Anal. Chim. 28. K. Dittrich, H. Fuchs, H. Berndt, J. A. C. Broekaert, and G. Acta, 2009, 647, 137. Schaldach, Fresenius J. Anal. Chem., 1990, 336, 303. 4. S. Gunduz and S. Akman, Food Chem., 2015, 172, 213. 29. E. Bulska, “Encyclopedia of Analytical Chemistry”, ed. 5. World Health Organization (WHO), Safety Evaluation of R. A. Meyers, 2009, John Wiley & Sons Ltd., Chichester, UK. Certain Food Additives, WHO Food Additives Series 42, 30. J. S. Gois, S. J. M. Malderen, H. R. Cadorim, B. Welz, and International Pogramme on Chemical Safety, Sulfur F. Vanhaecke, Spectrochim. Acta, Part B, 2017, 132, 50. Dioxide and Sulfites (addendum), 1999. 31. N. Ozbek and S. Akman, J. Agric. Food Chem., 2013, 61, 6. S. Gunduz and S. Akman, Lwt-Food Sci. Technol., 2014, 4816. 59, 718. 32. B. Welz, M. G. R. Vale, S. Florek, M. Okruss, M. D. Huang, 7. D. Mischek and C. Krapfenbauer-Cermak, Food Addit. and H. Becker-Ross, “Encyclopedia of Analytical Contam., 2012, 29, 371. Chemistry”, ed. R. A. Meyers, 2010, Wiley, Hoboken, NJ. 8. E. Papadopoulou-Mourkidou, J. Assoc. Off. Anal. Chem., 33. N. Ozbek and A. Baysal, Food Chem., 2015, 168, 460.