BS-ISO-17239-2004.pdf

BRITISH STANDARD BS ISO 17239:2004 Fruits, vegetables and derived products Determination of arsenic content Method using hydride generation atomic absorption spectrometry ICS 67.080.01 ? Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS ISO 17239:2004 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 18 October 2004 © BSI 18 October 2004 ISBN 0 580 44618 2 National foreword This British Standard reproduces verbatim ISO 17239:2004 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee AW/100, Agriculture and food, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to iv, pages 1 to 10, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Reference number ISO 17239:2004(E) © OSI 4002 INTERNATIONAL STANDARD ISO 17239 First edition 2004-10-15 Fruits, vegetables and derived products Determination of arsenic content Method using hydride generation atomic absorption spectrometry Fruits, légumes et produit dérivés Détermination de la teneur en arsenic Méthode par spectrométrie d'absorption atomique à génération de hydrure BS ISO 17239:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 17239:2004(E) DPlcsid Fremia ihTs PDF file may ctnoian emdebt dedyfepcaes. 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In tlnu ehikletneve y ttah lborp aem leratign to it is f,dnuo lpsaee inform ttneC ehlar Secrteiraat ta the serddaig sleb nevwo. © ISO 4002 Athgir lls serevr.de selnUs towrehise specfidei, trap on fo thsi ilbupctanoi may cudorper ebtu ro dezilina ni dey fomr yb ro nam y,snae lecetrinoc ro mecinahcal, inclidung tohpcoiypodna gn micrfoilm, wittuoh repmissii non writign from eitI rehSa Ot tsserdda eh ebolw or IS'Os memreb i ydobn the cnuotrfo y ttseuqer ehe.r ISO cirypothg fofice saCe tsopale 65 eneG 1121-HC 02 av leT. 4 + 10 947 22 1 11 xaF0 947 22 14 + 9 74 E-mail coirypthgiso.o gr We bwww.is.o gro Pulbisdehi n Switlrez dna ii © ISO 4002 Allr ithgsr esedevr BS ISO 17239:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:93271 O4002(E) I ©SO 4002 All irthgs ersedevr iii Contents Page Forewordiv 1 Scope 1 2 Principle. 1 3 Reagents 1 4 Apparatus 2 5 Sample 3 6 Procedure 3 7 Calculation. 5 8 Precision 5 9 Test report . 6 Annex A (normative) Apparatus . 7 Annex B (informative) Results of the interlaboratory test 9 Bibliography . 10 BS ISO 17239:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:93271 O4002(E) iv I ©SO 4002 All irthgs ersedevr Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. International Standard ISO 17239 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 3, Fruit and vegetable products. BS ISO 17239:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI INTENRATIONAL TSANDADR IS:93271 O4002(E) I ©SO 4002 All irthgs ersedevr 1 Fruits, vegetables and derived products Determination of arsenic content Method using hydride generation atomic absorption spectrometry 1 Scope This International Standard specifies a hydride generation atomic absorption spectrometric method for the determination of the arsenic content of fruits, vegetables and derived products. NOTE The method of arsenic determination in fruit, vegetables and derived products is based on AOAC Official Methods for Analysis (see Reference 1). 2 Principle Organic matter is decomposed by digestion with HNO3 in a closed system. Arsenic(V) is reduced to arsenic(III) with potassium iodide, and hydrides of arsenic are generated by the action of sodium borohydride prior to atomization in a flame-heated quartz cell. Measurement is by atomic absorption spectrometry. 3 Reagents Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or demineralized water or water of equivalent purity. 3.1 Nitric acid, concentrated, (20 = 1,38 g/ml). 3.2 Hydrochloric acid, 8 mol/l solution. Place 66 ml of concentrated hydrochloric acid (20 = 1,19 g/ml) in a 100 ml one-mark volumetric flask and make up to the mark with water. Mix. 3.3 Hydrochloric acid, diluted 1 + 1, by volume. Mix one volume of concentrated hydrochloric acid (20 = 1,19 g/ml) with one volume of water. 3.4 Magnesium chloride, 37,5 mg/ml solution. Dissolve, in a 100 ml one-mark volumetric flask, 3,75 g of magnesium oxide by gradually adding approximately 20 ml of hydrochloric acid solution (3.2) and make up to the mark with water. Mix. 3.5 Magnesium nitrate, 75 mg/ml solution. Dissolve, in a 50 ml one-mark volumetric flask, 3,75 g of magnesium oxide with approximately 30 ml of water. Slowly add approximately 10 ml of nitric acid (3.1) and mix. Make up to the mark with water. BS ISO 17239:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ISO 17239:2004(E) 2 I ©SO 4002 All irthgs ersedevr 3.6 Sodium borohydride, 4 % solution. Dissolve, in a 100 ml one-mark volumetric flask, 4 g of NaBH4 in 4 % sodium hydroxide. Mix and make up to the mark with 4 % sodium hydroxide. 3.7 Potassium iodide, 20 % solution. Dissolve, in a 100 ml one-mark volumetric flask, 20 g of potassium iodide in water. Mix and make up to the mark with water. Prepare just before use. 3.8 Arsenic, standard solution corresponding to 1,0 mg of arsenic per millilitre. 4 Apparatus Rinse all glassware before using with a nitric acid solution (diluted 1 + 1), followed by a thorough rinse with water. Decontaminate the digestion vessels by digesting with reagents to be used in digestion. Rinse thoroughly with water. Usual laboratory apparatus and, in particular, the following. 4.1 Mechanical grinder, the inside and blades of which are coated with polytetrafluoroethylene (PTFE). 4.2 Atomic absorption spectrometer, provided with an air/acetylene burner (10 cm) and hydrogen- nitrogen-entrained air flames, suitable for measurement at a wavelength of 193,7 nm and equipped with a deuterium-arc background correction. 4.3 Decomposition vessel, 70 ml (see Figure A.1), consisting of a stainless steel body supporting a polytetrafluoroethylene (PTFE) crucible having a screw-cap with a PTFE liner to provide a PTFE sealing surface. A PTFE spout is snapped on outside the rim to permit a quantitative transfer of the contents without contacting the metal parts. 4.4 Oven, capable of maintaining a temperature of 150 °C. 4.5 Furnace, capable of maintaining a temperature of 450 °C. 4.6 Hydride generator, (see Figure A.2), constructed from the following: 4.6.1 Flat-bottom flask, borosilicate glass, 50 ml capacity. 4.6.2 Stoppers, two-hole (one through the centre), No 9 rubber stopper, with a gas-outlet tube of polyethylene tubing, 100 mm long with a 3,2 mm id, fitted through the centre hole. 4.6.3 Reagent-cup assembly, consisting of the bottom 25 mm of a polyethylene test tube with a hole in the bottom, through which the lower end of a gas-outlet tube is placed so that 3 mm of a tube protrudes below the lower edge of the test tube. Connect the other end of the outlet tubing to the atomic absorption spectrometer (4.2) with 500 mm Tygon1) tubing by cutting the auxiliary line approximately 75 mm from the mixing chamber and attaching the tubing. 1) Tygon is the trade name of a product. This information is only given for the convenience of users of this International Standard and does not constitute an endorsement by ISO of this product. BS ISO 17239:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:93271 O4002(E) I ©SO 4002 All irthgs ersedevr 3 4.6.4 N2 inlet tube, made by sealing the bottom end of a segment of polyethylene tubing, 75 mm long with a 3,2 mm id, with a burner and then punching several holes in the sealed end with a 21-gauge needle which is inserted through the second hole of the stopper. Alternatively, prepare a segment of polyethylene tubing 500 mm long with a 1,6 mm id in a similar manner which is secured in place in the stopper with a hole-through septum. 4.6.5 Generator mount (optional), consisting of a segment of pipe, 64 mm long with a 1,3 mm id, secured to a laboratory ring stand by means of a clamp holder. Insert an extension clamp into the pipe and attach another clamp to the back of clamp to hold clamp in place and to serve as a handle. The clamp is now free to rotate 180°. Attach the rubber stopper of the hydride generator to the extension clamp with a stiff wire and position just at the level of the clamp jaws. In operation, place the flask of the generator between the jaws of the extension clamp, insert the stopper firmly into the neck of the flask, then tighten the clamp jaws around neck of the flask. The unit can be rapidly and uniformly inverted by rotating the handle on extension clamp, thus allowing the sample and the sodium borohydride to mix rapidly and reproducibly. 4.7 Pipettes, of appropriate capacities. 4.8 One-mark volumetric flasks, 10 ml, 50 ml and 200 ml capacity. 4.9 Analytical balance. 5 Sample It is important that the laboratory receive a sample that is truly representative and that has not been damaged or changed during transport or storage. 6 Procedure 6.1 Preparation of test sample Thoroughly mix the laboratory sample. If necessary, first remove any seeds, stalks and hard seed-cavity walls, and then grind in the mechanical grinder (4.1). Frozen or deep-frozen products shall be previously thawed in a closed vessel, and the liquid formed during this process shall be added to the product before mixing. 6.2 Test portion Weigh, to the nearest 0,01 g, 0,3 g (dry basis) of the test sample (6.1) into the decomposition vessel (4.3). 6.3 Decomposition CAUTION Do not exceed manufacturers' specification of 0,3 g of solids in a 70 ml vessel. Proceed cautiously with new or untried applications. Let such sample stand with nitric acid (3.1) overnight or heat on a hot plate cautiously until any vigorous reaction subsides. Then proceed with the closed vessel digestion. Open the vessel in a hood since nitrogen oxides are released. If the test portion contains ethanol, remove the ethanol by evaporation. Add 5 ml of nitric acid (3.1), close the vessel with a lid, and heat at 150 °C in the oven (4.4) for 2 h. Cool in a hood, remove the vessel from the jacket, and transfer the contents to a 10 ml volumetric flask (4.8). BS ISO 17239:2004 Licensed Copy: sheffieldun sheffieldun, na, Mon Nov 27 03:40:23 GMT+00:00 2006, Uncontrolled Copy, (c) BSI IS:93271 O4002(E) 4 I ©SO 4002 All irthgs ersedevr Add 4 ml of water to the vessel, cover with the lid, and while holding the lid tightly against the rim, invert several times, and add rinse to the flask. Dilute to the volume mark with water and mix. 6.4 Blank test Prepare a blank solution using the same decomposition procedure (6.3), but replacing the test portion (6.2) with 1 ml of water. 6.5 Determination 6.5.1 Preparation of calibration graph Dilute the standard arsenic solution (3.8) with water to obtain five solutions with an arsenic concentration of 1 µg/ml, 2 µg/ml, 3 µg/ml, 4 µg/ml, or 5 µg/ml. Add 2,0 ml of magnesium chloride solution (3.4) to each of a series of six 50 ml one-mark volumetric flasks (4.8). Add 50 µl of one of the standard solutions with an arsenic concentration of 1 µg/ml, 2 µg/ml, 3 µg/ml, 4 µg/ml, or 5 µg/ml to flasks two to six. These six flasks now contain 0 µg, 0,05 µg, 0,10 µg, 0,15 µg, 0,20 µg, or 0,25 µg of arsenic. Other amounts of arsenic may be used depending on sensitivity of a system. Add 0,1 ml of potassium iodide solution (3.7) to each flask, mix, and