Determination of Total Inorganic Arsenic in Fruit Juice Using High-Pressure Capillary Ion Chromatography

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1 etermination of Total Inorganic rsenic in Fruit Juice Using High-Pressure apillary Ion hromatography Hua Yang, Terri hristison, Linda Lopez Thermo Fisher Scientific, Sunnyvale,, US Technical Note 5 Key Words onductivity etection, Food and everage, High Resolution, Total Inorganic rsenic, 4 µm olumn Goal emonstrate the determinations of total inorganic arsenic in fruit juice using high-pressure capillary Ion hromatography (I). Introduction Growing interest around arsenic (s) determinations in fruit juices has been triggered by media claims of total arsenic concentrations above acceptable limits in apple juice products. lthough the F has been testing and monitoring fruit juices for arsenic content for more than 0 years and has found that total inorganic arsenic levels in juice are typically low, more recently there has been heightened scrutiny of arsenic in apple juice., The U.S. EP has set the total arsenic standard for drinking water at 0.0 parts per million (ppm). 4 However, total arsenic determinations can be misleading because inorganic arsenic compounds (arsenate s(v) and arsenite s(iii)) are highly toxic, whereas organic arsenic compounds have much lower toxicity. 5,6 The established analytical method for the various arsenic species is separation by I followed by detection using Inductively oupled Plasma Mass Spectrometry (IP-MS). 7,8 I with suppressed conductivity detection () is a well established, complimentary method used by multiple industries for ionic determinations. 9 This method has been demonstrated to be an excellent way to characterize fruit juices and wine., The recently introduced high-pressure capable capillary I systems combined with 4 μm particle ion-exchange columns have reduced eluent consumption and further improved separation efficiency. This study presents the detection and quantification of total inorganic arsenic (rsenate s(v) and rsenite s(iii)) in fruit juices separated on a high-resolution 4 µm particle anion exchange column using a high-pressure capillary I system. Equipment Thermo Scientific ionex IS HPI high-pressure capillary I system: Thermo Scientific ionex IS etector/hromatography module with high-pressure degas cartridge Thermo Scientific ionex I ube Thermo Scientific ionex IS P ual Pump module with high-pressure capillary pumps Thermo Scientific ionex IS EG Eluent Generator module Thermo Scientific ionex S-P utosampler Thermo Scientific ionex hromeleon 7. hromatography ata system (S) software

2 Reagents and Standards Stock standards: 00 mg/l of individual anion stock standards were prepared by dissolving acids or salts in 8 MW-cm resistivity deionized water. Reagent needed to prepare L of anion stock are listed in Table Mixed working standard (mixed S): working standard solution was prepared by mixing the stock standards to the concentrations indicated in Table with deionized water rsenate calibration standards: The arsenate calibration standards were prepared by diluting the arsenate stock solution with deionized water. 0., 0.5,.0, 4.0, 5.0,, 5, 50, and 0 mg/l arsenate standards were used ll S grade reagents were purchased from Fisher Scientific The amounts of compounds used to prepare L of 00 mg/l anion stock standards and the anion concentrations in mixed working standard are described below (Table ). Sample Preparation ommercial juice samples were filtered with a syringe filter (0.0 µm), and then diluted 50-fold with deionized water. Fifty-fold diluted juice samples were spiked with 0.9 and 0.50 mg/l arsenate. Note: It is important to use 8 MW-cm resistivity, deionized water for standard, eluent, and autosampler flush solutions to avoid system contamination, decreased sensitivity, and poor calibration. egassing the deionized water by vacuum filtration prior to use is a good practice. onditions Ion hromatography Instrument: ionex IS HPI system olumn: Thermo Scientific ionex IonPac S-H-4µm column ( mm) olumn Temp.: I ube Temp.: 5 Eluent Source: Thermo Scientific ionex EG KOH artridge (apillary) Gradient: Flow Rate:.5 mm KOH (- 0 min);.5 mm KOH (0 min); 8 mm ( min); 8 8 mm ( 5 min); 8 5 mm (5 min); 5 65 mm ( 4 min); 65 mm (4 8 min) 0.05 ml/min etection: System ackpressure: ~00 psi Suppressed conductivity, utosuppression Thermo Scientific ionex ES 0 nion apillary Electrolytic Suppressor, recycle mode, m Part numbers of the consumables used in this document are listed in Table. Table. Standard preparation table. nion Reagent Weight* (g) Mixed S (mg/l) Quinate Quinic acid Fluoride Sodium fluoride.. Lactate Lithium lactate cetate Sodium acetate, trihydrate.5.4 Glycolate Glycolic acid.000 Propionate Sodium propionate Formate Sodium formate.5.4 utyrate Sodium butyrate Pyruvate Pyruvic acid Valerate Valeric acid.000 Galacturonate -Galacturonic acid, monohydrate.000. romate Sodium bromate hloride Sodium chloride Nitrite Sodium nitrite romide Sodium bromide.88. Nitrate Sodium nitrate.7.5 Glutarate Glutaric acid.000. nion Reagent Weight* (g) Mixed S (mg/l) Succinate Sodium succinate.96. Malate L-Malic acid.000 Malonate Malonic acid Tartrate Sodium tartrate. Maleate Maleic acid Sulfate Sodium sulfate Oxalate Sodium oxalate Fumarate Fumaric acid Phosphate Potassium phosphate, monobasic.4 9. itrate itric acid Isocitrate Isocitric acid, trisodium dihydrate cis-conitate cis-conitic acid trans-conitate trans-conitic acid rsenate Sodium arsenate, dibasic heptahydrate rsenite Sodium meta-arsenite.5 * Reagent needed to prepare L of 00 mg/l anion stock.

3 Table. onsumables list. Product Name ionex EG-KOH cartridge (apillary) Thermo Scientific ionex R-T ontinuously Regenerating nion Trap olumn (apillary) ionex IonPac S-H-4µm column Thermo Scientific ionex R 80 arbonate Removal evice (apillary) ionex ES 0 nion apillary Electrolytic Suppressor ionex HP fittings (blue) EG egas HP cartridge ionex S-P utosampler vials ionex IonPac T-500 column escription Eluent Generator cartridge Electrolytic capillary trap column Part Number Separation column 0780 arbonate removal device cartridge Suppressor cartridge 0705 olts/ferrules High-pressure degas cartridge, up to 5000 psi Package of 0, ml polystyrene vials, caps, blue septa / nion trap column Instrument Setup and Installation To achieve the best chromatography with capillary I, it is important to minimize void volumes in each connection by using precision cut tubing, high pressure connectors and fittings (blue color), and seating the ferrule > mm above the end of the tubing. Extra care should be used to prevent air in all consumables or tubing by observing steady liquid flow before installing the next device in line. thorough discussion can be found in Thermo Scientific Technical Note (TN) : Practical Guidance for apillary I. ionex S-P utosampler Fresh 8 MΩ-cm Resistivity eionized Water Syringe Tray arousel Figure. Flow diagram. Figure. ionex I ube. Needle * High-Pressure up to 5000 psi ** Green line is the flow path diagram for Regen and dashed line flows through the back of the I ube R 80 ES Suppressor olumns ES Suppressor Internal Sample Loop ionex IS HPI apillary System Regen** egas Module artridge* Regen** Regen** R 80 R-T* Waste Guard and Separation olumns 4-Port Injection Valve EG* T* EG egas HP artridge Fresh 8 MΩ-cm Resistivity eionized Water Pump* Side view of ionex ES Suppressor Figure shows the flow diagram of this application. EG egas HP, ionex arbonate Removal evice, and ionex ES suppressor cartridges and both columns are installed in the ionex I ube (Figure ). Prior to use, the ionex ES suppressor and ionex R-T trap column should be hydrated, and the ionex EG cartridge and ionex IonPac columns should be conditioned. The instructions can be found in section.8 of the ionex IS HPI system installation manual. 5 etailed instructions are also described in Thermo Scientific TN : onfiguring High-Pressure apillary I on the Modular I System, the product manuals, and the instrument installation and operator s manuals. 9

4 4 Results and iscussion The ionex IonPac S-H columns are well known for their ability to separate a large variety of anions, including organic and inorganic acids in fruit juices and wine., The newly introduced 4 µm resin particle technology has further increased chromatographic efficiency and improved resolution with higher operating pressures. ionex IS HPI system, capable of handling pressures up to 5000 psi, and a ionex IonPac S-H-4μm capillary column were selected for this study. Ion chromatography with suppressed conductivity detection has been demonstrated to be an excellent way to characterize fruit juices and wine. With minimum modification, such as adding shallow gradients at the beginning to increase resolution of early eluting peaks and between 8 to 5 minutes to achieve a baseline resolution of arsenate and citrate, a less than minute method was developed for arsenic analysis. The chromatogram in Figure is a mixed working standard for fruit juice analysis. This shows the separation of 7 organic and inorganic acids in a single injection. However, some critical pairs, such as glycolate/acetate, valerate/galacturonate, succinate/malate, and malonate/ tartrate, cannot be separated without adding an organic modifier. oelutions were proved by injection of individual acid standard and their mixture. cetate, galacturonate, succinate and tartrate were selected for inclusion in the standard mix due to their likelihood to be in juices. With this method, arsenate eluted at.9 minutes (Peak ) and was well resolved from citrate (Peak 4) indicating that the parameters used are appropriate for arsenate analysis in fruit juices. olumn: ionex IonPac S-H-4µm column, mm Instrument: ionex IS HPI system Eluent Source: ionex EG-KOH cartridge (apillary) Gradient (KOH):.5 mm (- min), 8 mm ( min), 5 65 mm ( 4 min), 65 mm (4 8 min) olumn Temp.: I ube Temp.: 5 etection: Suppressed conductivity, ionex ES 0 Suppressor, utosuppression, recycle mode Quinate Glutarate.. Fluoride.. Malate/Succinate.. Lactate.7 7. Malonate/Tartrate cetate.4 8. Maleate Propionate Sulfate.0 6. Formate.4 0. Oxalate utyrate 9.4. Fumarate Pyruvate.8. Phosphate Galacturonate.. rsenate 9.4. romate itrate 5.4. hloride Isocitrate 9.5. Nitrite cis-conitate.4. romide. 7. trans-conitate.8. Nitrate Figure. Mixed working standard.

5 5 To evaluate the linearity response to concentration, a calibration curve for arsenate was generated using replicate injections of 0. to 0 mg/l arsenate (Figure 4). ased on the signal to noise ratio (S/N), the arsenate LO is 0.06 mg/l (S/N =, n = 5) and LOQ is mg/l (S/N =, n = 5). The LO and LOQ for total arsenic (s) is 0.0 and mg/l respectively. These LOs/LOQs values approximate the EP arsenic limit for drinking water of 0.0 ppm and well below the reported Lowest-Observed-dverse-Effect Level (LOEL) of 0.7 mg/l. 4,5.0 r = %RS =.67 olumn: ionex IonPac S-H-4µm column, mm Instrument: ionex IS HPI system Eluent Source: ionex EG-KOH cartridge (apillary) Gradient (KOH):.5 mm (- min), 8 mm ( min), 5 65 mm ( 4 min), 65 mm (4 8 min). olumn Temp.: I ube Temp.: 5 etection: Suppressed conductivity, ionex ES 0 Suppressor, utosuppression, recycle mode Samples etected rsenate (mg/l) : Water blank : mg/l arsenate.0 mg/l arsenite : Sample at ph =. : Sample at ph = 7.0 E: Sample at ph =.0 rea (*min) *min Peak : Unknown : rsenate : Unknown rsenate (mg/l) Figure 4. alibration curve of arsenate from 0. to 0 mg/l E uring these experiments, a separate arsenite peak was not detected with this method. Interestingly, a corresponding concentration of arsenate was detected whenever arsenite was injected. To evaluate this hypothesis, mg/l arsenate, mg/l arsenite standards were tested neet (without treatment) and adjusted to ph and ph. Figure 5 shows that freshly prepared arsenite samples were converted during the analysis to arsenate under acidic, neutral or basic conditions. 0 5 Figure 5. rsenite detected as arsenate. 5 Researchers previously reported the conversion of s(iii) to s(v), and vice versa. 0 study by Segura et al., had shown that s(iii) in wastewater is transformed into s(v) at most phs. More recently, another researcher reported that almost 0% of s(iii) is converted to s(v) in tetramethylammonium hydroxide under basic conditions. The eluent for this method, KOH, is also a strong base, which converts arsenite to arsenate during the analysis. ecause both arsenite and arsenate are measured as arsenate, this is a suitable alternative method for total inorganic arsenic determinations.

6 6 Sample nalysis The method was applied to six juice samples (grape, mango, cranberry juice cocktail) and three brands of apple juices. Figures 6 show the chromatograms of juice samples over-laid with water blank and arsenate spiked juice samples. The chromatograms show that only the apple juice samples had a peak at the arsenate retention time. s demonstrated in these chromatograms, this method can characterize and quantify the organic acids, as well as, total inorganic arsenic in juices. ecause the method detects most of the acids present in fruit juice, it can not only be used to detect low levels of inorganic arsenic, it can also be used to obtain an acid profile that is characteristic of a particular juice or wine., These chromatograms demonstrate the differences in composition between the various fruit juice samples. For example, apple juice contains 9 anions with succinate (or malate), galacturonate, and quinate being present at the highest concentrations (Figure 6). olumn: ionex IonPac S-H-4µm column, mm Instrument: ionex IS HPI system Eluent Source: ionex EG-KOH cartridge (apillary) Gradient (KOH):.5 mm (- min), 8 mm ( min), 5 65 mm ( 4 min), 65 mm (4 8 min) olumn Temp.: I ube Temp.: 5 etection: Suppressed conductivity, ionex ES 0 Suppressor, utosuppression, recycle mode Samples: : Water : 50-fold dilution of apple juice Sample : 0. mg/l arsenate spiked Sample : 0.5 mg/l arsenate spiked Sample. Quinate 6.. Malate/Succinate 7.5. Fluoride.0. Sulfate.5. Lactate.. Oxalate. 4. cetate/glycolate.7. Phosphate.9 5. Formate.6 5. Unknown 6. Pyruvate 0.4. rsenate* 7. Galacturonate itrate hloride Isocitrate Nitrate. 9. trans-conitate 0.. Glutarate Unknown Figure 6. Inorganic anions, organic acids, and arsenate in a diluted apple juice sample.

7 7 Grape juice contains 8 anions with galacturonate, malonate (or tartrate), and succinate (or malate) being present at the highest concentrations (Figure 7). The mango juice sample in Figure 8, shows predominantly citrate with minor concentrations of other organic acids. olumn: ionex IonPac S-H-4µm column, mm Instrument: ionex IS HPI system Eluent Source: ionex EG-KOH cartridge (apillary) Gradient (KOH):.5 mm (- min), 8 mm ( min), 5 65 mm ( 4 min), 65 mm (4 8 min) olumn Temp.: I ube Temp.: 5 etection: Suppressed conductivity, ionex ES 0 Suppressor, utosuppression, recycle mode Samples: : Water : 50-fold dilution of a grape juice sample : 0. mg/l arsenate spiked Sample : 0.5 mg/l arsenate spiked Sample 5. Quinate.8. Malate/Succinate 9.7. Lactate.. Malonate/Tartrate 6.6. cetate.9. Sulfate Formate.6. Oxalate.5 5. Pyruvate 0.4. Phosphate Galacturonate Unknow na 7. hloride.4. rsenate* 8. Nitrate.0 7. itrate.9 9. Glutarate na 8. Isocitrate trans-conitate na 0.7 olumn: ionex IonPac S-H-4µm column, mm Instrument: ionex IS HPI system Eluent Source: ionex EG-KOH cartridge (apillary) Gradient (KOH):.5 mm (- min), 8 mm ( min), 5 65 mm ( 4 min), 65 mm (4 8 min) olumn Temp.: I ube Temp.: 5 etection: Suppressed conductivity, ionex ES 0 Suppressor, utosuppression, recycle mode Samples: : Water : 50-fold dilution of a mango juice sample : 0. mg/l arsenate spiked into Sample : 0.5 mg/l arsenate spiked into Sample. Quinate.. Maleate 0.. Lactate.. Sulfate 0.6. cetate.. Oxalate Formate 0.5. Phosphate.0 5. Galacturonate 0.6. rsenate* 6. hloride itrate Nitrate 0.7. Isocitrate Malate/Succinate. 9. Malonate/Tartrate Figure 7. Inorganic anions, organic acids, and arsenate in a diluted grape juice sample Figure 8. Inorganic anions, organic acids, and arsenate in a diluted mango juice sample.

8 8 ranberry cocktail juice also contains 8 anions, but the anions at the highest concentration are quinate, succinate (or malate) and citrate (Figure 9). olumn: ionex IonPac S-H-4µm column, mm Instrument: ionex IS HPI system Eluent Source: ionex EG-KOH cartridge (apillary) Gradient (KOH):.5 mm (- min), 8 mm ( min), 5 65 mm ( 4 min), 65 mm (4 8 min) olumn Temp.: I ube Temp.: 5 etection: Suppressed conductivity, ionex ES 0 Suppressor, utosuppression, recycle mode Samples: : Water : 50-fold dilution of a cranberry cocktail juice sample : 0. mg/l arsenate spiked into Sample : 0.5 mg/l arsenate spiked into Sample Quinate 8.8. Malate/Succinate 4.4. Fluoride 0.. Maleate 0.8. Lactate 0.4. Sulfate cetate 0.6. Oxalate 5. Formate 0.. Phosphate Pyruvate Unknown na 7. Galacturonate 7.5. rsenate* 8. hloride itrate Nitrate Isocitrate trans-conitate Figure 9. Inorganic anions, organic acids, and arsenate in a diluted cranberry cocktail juice. The profile of juices can be used to assess whether an expensive juice has been illegally adulterated with a lower cost juice such as cranberry with apple juice (Figure ). ecause the peak ratio of malate/succinate to quinate is high for apple juice (about to ) and low for cranberry juice (about to ), adding apple juice into cranberry juice is easily identified with this peak ratio. olumn: ionex IonPac S-H-4µm column, mm Instrument: ionex IS HPI system Eluent Source: ionex EG-KOH cartridge (apillary) Gradient (KOH):.5 mm (- min), 8 mm ( min), 5 65 mm ( 4 min), 65 mm (4 8 min). olumn Temp.: I ube Temp.: 5 etection: Suppressed conductivity, ionex ES 0 Suppressor, utosuppression, recycle mode Samples: : Water : mg/l arsenate in water : 50-fold dilution of apple juice Sample : 0.50 mg/l arsenate spiked Sample E: 50-fold dilution of apple juice Sample F: 50-fold dilution of apple juice Sample 0 0 F E F E Figure. Inorganic anions, organic acids, and arsenate in a diluted apple juice samples.

9 onclusion The high-pressure ionex IS HPI I system and the newly introduced Thermo Scientific ionex IS-00 capillary HPI system provide a solution for simple juice analysis. This technical note demonstrates that: High-pressure capillary I with suppressed conductivity detection () provides a sensitive method to detect and quantify arsenite (s(iii)) and arsenate (s(v)) as total inorganic arsenic, as well as characterizing organic acids With an arsenate LO of 0.06 mg/l and LOQ of mg/l, this method can be used to estimate the total inorganic arsenic (s) in juice at a LO of 0.0 mg/l and LOQ of mg/l, which is well below the EP reported LOEL of 0.7 mg/l References. Letters from the F to the r.oz Show Regarding pple juice and rsenic. [Online] gov/food/resourcesforyou/onsumers/ucm7746. htm (accessed Feb., 0).. rsenic in pple Juice. [Online] Food/FoodborneIllnessontaminants/Metals/ ucm8009.htm (accessed Feb., 0).. F Widens Look at rsenic in pple Juice. [Online] ucm85.htm (accessed Feb., 0). 4. rsenic in rinking Water. [Online] epa.gov/lawsregs/rulesregs/sdwa/arsenic/index.cfm (accessed Feb., 0). 5. rsenic, inorganic (SRN74-8-). [Online] (accessed Feb., 0). 6. rsenic. [Online] securit/chem-chim/environ/arsenic-eng.php (accessed Feb., 0). 7. EP-85-R-00-0, nalytical Methods Support ocument For rsenic In rinking Water [Online] methods.pdf (accessed Feb., 0). 8. Thermo Fisher Scientific. pplication Note 499, I-IP-MS speciation analysis of s in apple juice using the Thermo Scientific ip Q IP-MS, N499_E 0/, Sunnyvale,, Thermo Fisher Scientific, pplication Update 54, U 54 etermination of Inorganic nions in Wastewater in Environmental Waters Using a Hydroxide-Selective olumn, LPN 59, Sunnyvale,, 00.. Thermo Fisher Scientific, pplication Note, N Quantification of nions in Pharmaceuticals, LPN 094, Sunnyvale,, 00.. Thermo Fisher Scientific, pplication Note 5, N 5 Monitoring for Trace nion ontamination in the Extracts of Electronic omponents, LPN 57, Sunnyvale,, 00.. Thermo Fisher Scientific, pplication Note, N etermination of Organic cids in Fruit Juices, LPN 5, Sunnyvale,, 00.. Thermo Fisher Scientific, pplication Note 7, N 7 Higher Resolution Separation of Organic cids and ommon Inorganic nions in Wine, LPN 77, Sunnyvale,, 0.. Thermo Fisher Scientific. Technical Note, TN Practical Guidance for Using apillary nion hromatography, LPN 4, Sunnyvale,, Thermo Fisher Scientific. ionex IS Installation Manual, oc No , Sunnyvale,, 0.. Thermo Fisher Scientific. Technical Note, TN onfiguring High-Pressure apillary I on the Modular I System, ocument No. TN705_E /S, Sunnyvale,, Thermo Fisher Scientific. Product Manual for the ontinuously Regenerated Trap olumn (R-T), oc No. 09, Sunnyvale,, Thermo Fisher Scientific. Product Manual for ES 0 Suppressors, oc No , Sunnyvale,, Thermo Fisher Scientific. ionex S-P Operator s Manual, oc No. 0656, Sunnyvale,, K.. Francesconi,. Kuehnelt, nalyst, 004, 9, M. Segura, J. Munoz, Y. Madrid and. amara, nal. ioanal. hem., 00, 74, omparison of rsenic Speciation Methods for iological Tissues. [Online] docs/0/presentations/monpm-metallic- Ugrai-8-6-.pdf (accessed Feb., 0). Technical Note Thermo Fisher Scientific Inc. ll rights reserved. ll trademarks are the property of Thermo Fisher Scientific and its subsidiaries. This information is presented as an example of the capabilities of Thermo Fisher Scientific products. It is not intended to encourage use of these products in any manners that might infringe the intellectual property rights of others. Specifications, terms and pricing are subject to change. Not all products are available in all countries. Please consult your local sales representative for details. frica ustralia ustria elgium razil anada hina (free call domestic) TN7088_E 09/M enmark Europe-Other Finland France Germany India Italy Japan Korea Latin merica Middle East Netherlands New Zealand Norway Russia/IS Singapore Sweden Switzerland Taiwan UK/Ireland US