EN 14627-2005 en Foodstuffs - Determination of trace elements - Determination of total arsenic and selenium by hydride generation atomic absorption spectrometry (HGAAS) after press.pdf

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1、BRITISH STANDARD BS EN 14627:2005 Foodstuffs Determination of trace elements Determination of total arsenic and selenium by hydride generation atomic absorption spectrometry (HGAAS) after pressure digestion The European Standard EN 14627:2005 has the status of a British Standard ICS 67.050 BS EN 146

2、27:2005 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 13 May 2005 BSI 13 May 2005 ISBN 0 580 46012 6 National foreword This British Standard is the official English language version of EN 14627:2005. The UK participation in its preparation

3、was entrusted to Technical Committee AW/-/3, Food analysis Horizontal methods, 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 or European publicat

4、ions 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 necess

5、ary 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 interp

6、retation, 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 EN title page, pages 2 to 15 and a back cover. The BSI copy

7、right notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEANSTANDARD NORMEEUROPENNE EUROPISCHENORM EN14627 April2005 ICS67.050 Englishversion FoodstuffsDeterminationoftraceelementsDeterminationof totalarsenica

8、ndseleniumbyhydridegenerationatomic absorptionspectrometry(HGAAS)afterpressuredigestion ProduitsalimentairesDosagedeslmentstraces Dosagedelarsenictotaletduslniumparspectromtrie parabsorptionatomiquepargnrationdhydrures (SAAGH)aprsdigestionsouspression LebensmittelBestimmungvonElementspuren Bestimmun

9、gvonGesamtarsenundSelenmit AtomabsorptionsspektrometrieHydridtechnik(HGAAS) nachDruckaufschluss ThisEuropeanStandardwasapprovedbyCENon15March2005. CENmembersareboundtocomplywiththeCEN/CENELECInternalRegulationswhichstipulatetheconditionsforgivingthisEurope an Standardthestatusofanationalstandardwith

10、outanyalteration.Uptodatelistsandbibliographicalreferencesconcernings uchnational standardsmaybeobtainedonapplicationtotheCentralSecretariatortoanyCENmember. ThisEuropeanStandardexistsinthreeofficialversions(English,French,German).Aversioninanyotherlanguagemadebytra nslation undertheresponsibilityof

11、aCENmemberintoitsownlanguageandnotifiedtotheCentralSecretariathasthesamestatusast heofficial versions. CENmembersarethenationalstandardsbodiesofAustria,Belgium,Cyprus,CzechRepublic,Denmark,Estonia,Finland,France, Germany,Greece,Hungary,Iceland,Ireland,Italy,Latvia,Lithuania,Luxembourg,Malta,Netherla

12、nds,Norway,Poland,Portugal, Slovakia, Slovenia,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2005CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwidef

13、orCENnationalMembers. Ref.No.EN14627:2005:EEN 14627:2005 (E) 2 Contents Foreword 3 1 Scope .4 2 Normative references .4 3 Principle.4 4 Reagents5 5 Apparatus and equipment8 6 Procedure 8 7 Calculation.10 8 Limit of quantification.10 9 Precision11 10 Test report .12 Annex A (informative) Results of t

14、he inter-laboratory tests13 Bibliography.15 EN 14627:2005 (E) 3 Foreword This document (EN 14627:2005) 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 given the status of a national sta

15、ndard, either by publication of an identical text or by endorsement, at the latest by October 2005, and conflicting national standards shall be withdrawn at the latest by October 2005. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries

16、are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland a

17、nd United Kingdom. EN 14627:2005 (E) 4 1 Scope This European Standard specifies two methods: one method for the determination of total arsenic and another method for the determination of selenium in foodstuffs by hydride generation atomic absorption spectrometry (HGAAS) after pressure digestion. Spe

18、cific foodstuffs for which European Standards exist are excluded from the scope of this horizontal European Standard. It is the task of the analyst to review if vertical standards exist. For the determination of total arsenic in high concentration in e.g. seafood, the method specified in EN 14332 ca

19、n be used. 2 Normative references The following referenced documents are indispensable for the application of this 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 Foodst

20、uffs Determination of trace elements Performance criteria, general considerations and sample preparation. EN 13805 Foodstuffs Determination of trace elements Pressure digestion. 3 Principle 3.1 General Determination of the element to be determined in the test solution by HGAAS after pressure digesti

21、on according to EN 13805. WARNING The use of this standard may involve hazardous materials, operations and equipment. This standard does not purport to address all the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate health and s

22、afety practices and determine the applicability or regulatory limitations prior to use. 3.2 Determination of total arsenic Arsenic ions are converted to arsenic hydride by sodium borohydride in an acid solution. Arsenic hydride is transferred by a gas stream into a heated measurement cell and decomp

23、osed. Arsenic is determined at 193,7 nm. Since arsenic (III) and arsenic (V) show a different sensitivity with the hydride technique, it is necessary to reduce arsenic (V) to arsenic (III) in order to avoid incorrect measurements. A digestion temperature up to 320 C may be necessary in order to enab

24、le the hydridisation of the arsenic compounds and in order to determine all different arsenic species in the foodstuff. NOTE This known fact in the case of materials of marine origin was additionally observed for Rice powder and Kidney powder during the inter-laboratory tests for this procedure. 3.3

25、 Determination of selenium Selenium ions are converted to selenium hydride by sodium borohydride in an acid solution. This selenium hydride is transferred by a gas stream into a heated measurement cell and decomposed. Selenium is determined at 196,0 nm. EN 14627:2005 (E) 5 Selenium (VI) is not deter

26、mined by the hydridisation as described here. It is therefore necessary to adjust the digestion conditions to yield only selenium (IV). Digestion temperatures greater than 280 C can lead to increased formation of selenium (VI). 4 Reagents 4.1 General The concentration of the element to be determined

27、 in the reagents and water used shall be low enough not to affect the results of the determination. Commercially available stock standard solutions should preferably be accompanied by a certificate (see 4.2.8 and 4.3.6). 4.2 Reagents for the determination of arsenic 4.2.1 Hydrochloric acid, 30 %, (m

28、ass concentration), (HCl) = 1,15 g/ml. 4.2.2 Nitric acid, at least 65 %, of approximately (HNO 3 ) = 1,4 g/ml. 4.2.3 Diluted nitric acid, mix nitric acid (4.2.2) and water in a proportion of 1 + 1 parts by volume. 4.2.4 Sodium borohydride solution, e.g. substance concentration c = 2 g/l (if, for exa

29、mple, the flow injection procedure is used, see 6.3.1 (3). Dissolve 2 g of sodium hydroxide pellets in water, add 2 g of sodium borohydride and dilute to 1000 ml with water. A fresh solution shall be prepared daily and filtered before use. The concentration by mass of the sodium borohydride solution

30、 may vary with the system and the instructions of the relevant manufacturer shall therefore be observed. 4.2.5 Diluted hydrochloric acid, e.g. mass fraction w = about 3 % (carrier solution, only for use in the flow injection procedure). Dilute approximately 90 ml of hydrochloric acid (4.2.1) to 1000

31、 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. 4.2.6 Potassium iodide/ascorbic acid solution Dissolve 3 g of potassium iodide and 5 g of ascorbic acid in water and dilute to 100

32、 ml. Prepare a fresh solution daily. The concentrations of the potassium iodide and ascorbic acid may vary slightly with the system and the instructions of the relevant manufacturer shall therefore be observed. 4.2.7 Hydroxyl ammonium chloride solution Dissolve 10 g of hydroxyl ammonium chloride in

33、100 ml of water. 4.2.8 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 diarsenic trioxide (As 2 O 3 ) in 25 ml of potassium hydroxide solution (c= 20 g/100 ml), neutralize with 20 % (mas

34、s fraction) sulfuric acid with EN 14627:2005 (E) 6 phenolphthalein as indicator and dilute to 1000 ml with 1 % (mass fraction) sulfuric acid. 4.2.9 Arsenic standard solutions Dilute the arsenic stock solution (4.2.8) in several steps. The arsenic standard solutions shall contain an adequate amount o

35、f hydrochloric acid, e.g. 2 ml of hydrochloric acid (4.2.1) 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 arsenic in 0,6 % (mass concentration) hydrochloric acid is stable for at least one week. 4.2.10 Arsenic calibration

36、 solutions Prepare five calibration solutions in the required calibration range from the standard solution of 0,1 mg/l (4.2.9), ensuring that the concentrations of the calibration solutions are not outside the linear range of the calibration function and are also in the expected sample content range

37、. 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 g/l 100 / 1010 g/l The calibration solutions may also be prepared from the appropriately diluted sta

38、ndard solution in the measurement vessel itself by adding the reagents for the pre-reduction (see 6.1.2). Prepare fresh calibration solutions daily. The following procedure is recommended for the preparation of standard and calibration solutions. Pour some water into the volumetric flask and add the

39、 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. 4.2.11 Zero member compensation solution, containing water and acid in a concentration equal to that in the sample solution. 4.3 Reagents for the determ

40、ination of selenium 4.3.1 Hydrochloric acid, 25 % (mass concentration), (HCl) = 1,13 g/ml. 4.3.2 Nitric acid, see 4.2.2. EN 14627:2005 (E) 7 4.3.3 Diluted nitric acid, see 4.2.3. 4.3.4 Sodium borohydride solution, see 4.2.4. The concentration by mass of the sodium borohydride solution may vary with

41、the system. The instructions of the relevant manufacturer shall therefore be observed. 4.3.5 Diluted hydrochloric acid, e.g. w = about 3 % (carrier solution, only for use in the flow injection procedure). Dilute approximately 110 ml of hydrochloric acid (4.3.1) to 1000 ml with water. The concentrati

42、on by mass of the carrier solution may vary with the system. The instructions of the relevant manufacturer shall therefore be observed. 4.3.6 Selenium stock solution, with a selenium concentration of 1000 mg/l. If commercial stock solutions are not available, proceed as follows: Dissolve 1,405 g of

43、selenium dioxide (SeO 2 ) and 2 g of sodium hydroxide in approximately 50 ml water, and dilute to 1000 ml with water. 4.3.7 Selenium standard solution Dilute the stock solution (4.3.6) in several steps. The solutions shall contain an adequate amount of hydrochloric acid, e.g. 2 ml of hydrochloric ac

44、id (4.3.1) 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 selenium in 0,5 % (mass fraction) hydrochloric acid is stable for at least one week. 4.3.8 Selenium calibration solutions Prepare five calibration solutions in the

45、required calibration range from the standard solution of 0,1 mg/l (4.3.7), ensuring that the concentrations of the calibration solutions are 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 soluti

46、ons 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 g/l 100 / 1010 g/l Prepare fresh calibration solutions daily. The following procedure is recommended for the preparation of standard and calibration solu

47、tions. 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. EN 14627:2005 (E) 8 4.3.9 Zero member compensation solution, see 4.2.11. 5 Apparatus and equ

48、ipment 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. 5.2 Atomic absorption spectrometer, with a measurement recording system and accessories for the hydride generation procedure. 5.3 Element-specific lamp for arsenic/sel