DIN EN 15517-2008 Foodstuffs - Determination of trace elements - Determination of inorganic arsenic in seaweed by hydride generation atomic absorption spectrometry (HGAAS) after ac.pdf

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1、September 2008DEUTSCHE NORM English price group 10No part of this standard may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 67.050; 71.040.50!$Q

2、o“1467693www.din.deDDIN EN 15517Foodstuffs Determination of trace elements Determination of inorganic arsenic in seaweed by hydride generationatomic absorption spectrometry (HGAAS) after acid extractionEnglish version of DIN EN 15517:2008-09Lebensmittel Bestimmung von Elementspuren Bestimmung von an

3、organischem Arsen in Meeresalgen mitAtomabsorptionsspektrometrie-Hydridtechnik (HGAAS) nach SureextraktionEnglische Fassung DIN EN 15517:2008-09SupersedesDIN EN 15517:2008-06www.beuth.deDocument comprises 16 pagesDIN EN 15517:2008-09 2 National foreword This standard has been prepared by Technical C

4、ommittee CEN/TC 275 “Food analysis Horizontal methods” (Secretariat: DIN, Germany). The responsible German body is the Normenausschuss Lebensmittel und landwirtschaftliche Produkte (Food and Agricultural Products Standards Committee), Technical Committee Schwermetalle (Elementspuren). The DIN Standa

5、rd corresponding to the International Standard referred to in this document is as follows: ISO 5725-1 DIN ISO 5725-1 Amendments Compared with DIN EN 15517:2008-06, the following amendment has been made to the German version only and does not affect the English text: a) The subclauses of clause 4 hav

6、e been renumbered. Previous editions DIN EN 15517: 2008-06 National Annex NA (informative) Bibliography DIN ISO 5725-1, Accuracy (trueness and precision) of measurement methods and results Part 1: General principles and definitions EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN 15517March 2008ICS

7、 67.050English VersionFoodstuffs - Determination of trace elements - Determination ofinorganic arsenic in seaweed by hydride generation atomicabsorption spectrometry (HGAAS) after acid extractionProduits alimentaires - Dosage des lments traces -Dosage de larsenic inorganique dans les algues marinesp

8、ar spectromtrie dabsorption atomique par gnrationdhydrures (SAAGH) aprs extraction acideLebensmittel - Bestimmung von Elementspuren -Bestimmung von anorganischem Arsen in Meeresalgen mitAtomabsorptionsspektrometrie-Hydridtechnik (HGAAS)nach SureextraktionThis European Standard was approved by CEN on

9、 7 February 2008.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may b

10、e obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Ma

11、nagement Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Nor

12、way, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2008 CEN All rights of exploitation in any form an

13、d by any means reservedworldwide for CEN national Members.Ref. No. EN 15517:2008: EEN 15517:2008 (E) 2 Contents Page Foreword3 1 Scope 4 2 Normative references 4 3 Principle4 4 Reagents.5 5 Apparatus and equipment 6 6 Procedure .7 7 Calculation9 8 Precision.9 9 Test report 10 Bibliography 14 DIN EN

14、15517:2008-09 Annex A (informative) Results of the inter-laboratory tests .11 EN 15517:2008 (E) 3 Foreword This document (EN 15517:2008) has been prepared by Technical Committee CEN/TC 275 “Food analysis - Horizontal methods”, the secretariat of which is held by DIN. This European Standard shall be

15、given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by September 2008, and conflicting national standards shall be withdrawn at the latest by September 2008. Attention is drawn to the possibility that some of the elements of this docum

16、ent may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: A

17、ustria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. DIN EN

18、 15517:2008-09EN 15517:2008 (E) 4 1 Scope This document specifies a procedure for the determination of hydrochloric acid (gastric acid concentration) extractable inorganic arsenic in seaweed. Collaborative studies have been carried out (Annex A). The method is suitable for the determination of inorg

19、anic arsenic not less than 1 mg/kg and below 100 mg/kg on a dry weight basis. The amount of inorganic arsenic is considered to be that part determined by the procedure described in this document. 2 Normative references The following referenced documents are indispensable for the application of this

20、document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 13804, Foodstuffs Determination of trace elements Performance criteria, general considerations and sample preparation 3 Princip

21、le Arsenic compounds are extracted from the sample by diluted hydrochloric acid (in accordance with EN 71-3 5) and the arsenic in the extract is determined by hydride generation AAS. In acidic media inorganic compounds of arsenic(III) and arsenic(V) as well as the monomethylarsonic acid (MMA) and di

22、methylarsinic (cacodylic) acid (DMA) form a volatile hydride with sodium borohydride. There is no reaction of the stable organic arsenic compounds like arsenosugar, arseno-betaine and arseno-choline under these conditions. The gaseous hydride is transferred into a heated measuring cell (cuvette) by

23、means of a carrier gas stream and decomposed. The absorption at 193,7 nm (arsenic line) serves as a measure of arsenic concentration. The hydride signal sensitivity of DMA reaches generally low rates as compared to As(III). The contribution of MMA in the hydride signal can be neglected, since MMA oc

24、curs in seaweed only in small amounts. The hydride generation AAS in combination with this hydrochloric acid extraction may be used as nearly selective method of determination for inorganic arsenic. Generation of arsine from As(III) is much faster and gives greater sensitivity than generation from A

25、s(V) and is also less subject to interference. Arsenic(V) shall be reduced to arsenic(III) (pre-reduction) in order to avoid incorrect measurements. DIN EN 15517:2008-09 EN 15517:2008 (E) 5 4 Reagents 4.1 General The concentration of arsenic in the reagents and water used shall be low enough not to

26、affect the results of the determination. 4.2 Hydrochloric acid, mass fraction w = 30 %, mass concentration (HCl) = 1,15 g/ml. 4.3 Hydrochloric acid solution, substance concentration c = (0,07 0,005) mol/l. 4.4 Hydrochloric acid, approximately c = 2 mol/l. 4.5 Sodium borohydride, w 96 % 4.6 Sodium hy

27、droxide, w 98 % 4.7 Sodium borohydride solution, e.g. substance concentration c = 2 g/l (example for using the flow injection procedure described under 6.2.1 (b). Dissolve 2 g of sodium hydroxide pellets in water, add 2 g of sodium borohydride and dilute to 1 000 ml with water. A fresh solution shal

28、l be prepared daily and filtered before use. The concentration by mass of the sodium borohydride solution may vary with the system and the instructions of the relevant manufacturer shall therefore be observed. 4.8 Diluted hydrochloric acid, e.g. mass fraction w 3 % (carrier solution, only for use in

29、 the flow injection procedure). Dilute approximately 90 ml of hydrochloric acid (4.2) to 1 000 ml with water. The concentration by mass of the carrier solution may vary with the system and the instructions of the relevant manufacturer shall therefore be observed. 4.9 L-Ascorbic acid, w(C6H8O6) 99,7

30、% 4.10 Potassium iodide, w(KI) 99,5 % 4.11 Potassium iodide/ascorbic acid solution Dissolve 3 g of potassium iodide and 5 g of ascorbic acid in water and dilute to 100 ml. Prepare a fresh solution daily. The concentrations of the potassium iodide and ascorbic acid may vary slightly with the system a

31、nd the instructions of the relevant manufacturer shall therefore be observed. 4.12 Diarsenic trioxide (As2O3), w(As2O3) 99,5 % 4.13 Arsenic stock solution, with an arsenic mass concentration of 1000 mg/l. If commercial stock solutions are not available, proceed as follows: dissolve 1,320 g of diarse

32、nic trioxide DIN EN 15517:2008-09 EN 15517:2008 (E) 6 (4.12) in 25 ml of potassium hydroxide solution ( = 20 g/100 ml), neutralize with 20 % (mass fraction) sulfuric acid with phenolphthalein as indicator and dilute to 1 000 ml with 1 % (mass fraction) sulfuric acid. 4.14 Arsenic standard solutions

33、Dilute the arsenic stock solution (4.13) in several steps. The arsenic standard solutions shall contain an adequate amount of hydrochloric acid, e.g. 2 ml of hydrochloric acid (4.2) per 100 ml. Example of a dilution series: 1000 mg/l 100/550 mg/l 50/55 mg/l 50/10,1 mg/l A standard solution of 5 mg/l

34、 arsenic in 0,6 % (mass fraction) hydrochloric acid is stable for at least one week. 4.15 Arsenic calibration solutions Prepare five calibration solutions in the required calibration range from the standard solution of 0,1 mg/l (4.14), ensuring that the concentrations of the calibration solutions ar

35、e not outside the linear range of the calibration function and are also in the expected sample content range. The concentration of acid in the calibration solutions shall be equal to that in the sample solution. Example for the 1 g/l to 10 g/l range: 0,1 mg/l 100/11 g/l 100/33 g/l 100/55 g/l 100/88

36、g/l 100/1010 g/l The calibration solutions may also be prepared from the appropriately diluted standard solution in the measurement vessel itself by adding the reagents for the pre-reduction (see 6.1.3). Prepare fresh calibration solutions daily. The following procedure is recommended for the prepar

37、ation of standard and calibration solutions: pour some water into the volumetric flask and add the requisite amount of acid. After cooling to room temperature, add the stock or standard solution using a pipette and dilute to the mark with water. 4.16 Zero member compensation solution, containing wat

38、er and acid in a concentration equal to that in the sample solution. 5 Apparatus and equipment 5.1 General To minimise the contamination, all apparatus that come into direct contact with the sample and the solutions shall be carefully pre-treated according to EN 13804. DIN EN 15517:2008-09 EN 15517:

39、2008 (E) 7 5.2 Atomic absorption spectrometer, with measurement recording system and accessories for the hydride generation method. 5.3 Element-specific lamp (hollow-cathode or electrodeless discharge lamp) for arsenic. 5.4 Centrifuge 5.5 Syringe filter (unit), pore size 0,45 m, diameter 25 mm, resi

40、stant to hydrochloric acid (4.4). Membranes of polyester or nylon have been proven suitable. 5.6 Indicator paper 5.7 Device for thermostating, at approximately 37 C. 5.8 Stirrer or shaking machine 6 Procedure 6.1 Sample preparation 6.1.1 General It is possible that extracted arsenic compounds are de

41、composed to inorganic arsenic, even when stored in a refrigerator. Therefore, determination by hydride generation AAS should be conducted as soon as possible, latest within one week. 6.1.2 Hydrochloric acid extraction In imitation of EN 71-3 the well homogenized sample is weighed (minimum weighed po

42、rtion 0,2 g) into a vessel, which is suitable for the extraction and allows sufficient agitation motion. The ratio of weighed portion to extracting agent (extractant) shall be 1:50 (1 part + 49 parts). Add the appropriate amount of hydrochloric acid solution (4.3) of approximately 37 C to the sample

43、 and mix for 1 min. Transfer one drop of this mixture onto indicator paper. If the pH is more than 1,5, add dropwise hydrochloric acid (4.4) while stirring until the pH value lies between 1,0 and 1,5. Continuously agitate (by stirring or shaking) the suspension at a temperature of approximately 37 C

44、 for 1 h and then allow it to stand for 1 h at approximately 37 C. Immediately afterwards solids shall be separated from the solution. First centrifuge for 10 min and then filter through a syringe filter (5.5). The extract shall be free of particles. The concentration of arsenic in the solution shou

45、ld be measured by hydride generation AAS as soon as possible. The extraction solution is stored in a suitable vessel in a refrigerator until measurement. 6.1.3 Pre-reduction Depending on the hydride system used, it may be necessary to use larger or smaller volumes than described below. The ratios sp

46、ecified shall, however, be maintained. Introduce and thoroughly mix 2 ml of calibration solution (4.15) and 2 ml of hydrochloric acid (4.2) into the measurement vessel of the hydride system. Then add 1 ml of potassium iodide/ascorbic acid solution (4.11) and again mix thoroughly. After leaving for 4

47、5 min at room temperature in an open vessel, dilute to 10 ml with water and mix thoroughly to obtain a solution ready for measuring. If the calibration solution is prepared in the measurement vessel itself, use the appropriate quantity of standard solution and dilute to 2 ml with the zero member com

48、pensation solution (4.16), then proceed as described above. Treat the zero member compensation and the sample solutions in the same way. Up to 2 ml hydrochloric acid extract according to 6.1.2 are used for the pre-reduction. If necessary, the dilutions are made with zero member compensation solution

49、 (4.16) prior to the pre-reduction. Compensate using less than 2 ml of sample solution by adding the appropriate amount of zero member compensation solution (4.16). DIN EN 15517:2008-09 EN 15517:2008 (E) 8 The acid and reducing-agent concentrations shall be the same in all the test solutions. Only seal the measurement vessels after diluting with water for the final mixing. Do not analyse yellow-coloured solutions as they give incorrect results (too low or too high). To avoid proble