BS EN 14546-2005 Foodstuffs - Determination of trace elements - Determination of total arsenic by hydride generation atomic absorption spectrometry (HGAAS) after dry ashing《食品 痕量元素.pdf

1、BRITISH STANDARD BS EN 14546:2005 Foodstuffs Determination of trace elements Determination of total arsenic by hydride generation atomic absorption spectrometry (HGAAS) after dry ashing The European Standard EN 14546:2005 has the status of a British Standard ICS 67.050 BS EN 14546:2005 This British

2、Standard was published under the authority of the Standards Policy and Strategy Committee on 16 May 2005 BSI 16 May 2005 ISBN 0 580 46011 8 National foreword This British Standard is the official English language version of EN 14546:2005. The UK participation in its preparation was entrusted to Tech

3、nical 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 publications referred to in t

4、his 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 c

5、ontract. 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 proposal

6、s 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 12, an inside back cover and a back cover. The BSI cop

7、yright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsEUROPEANSTANDARD NORMEEUROPENNE EUROPISCHENORM EN14546 April2005 ICS67.050 Englishversion FoodstuffsDeterminationoftraceelementsDeterminationof totalarsenic

8、byhydridegenerationatomicabsorption spectrometry(HGAAS)afterdryashing ProduitsalimentairesDterminationdeslmentstraces Dterminationdelarsenictotalparspectromtrie dabsorptionatomiquepargnrationdhydrures(SAAGH) aprscalcinationparvoiesche LebensmittelBestimmungvonElementspuren BestimmungvonGesamtarsenmi

9、t AtomabsorptionsspektrometrieHydridtechnik(HGAAS) nachTrockenveraschung ThisEuropeanStandardwasapprovedbyCENon15March2005. CENmembersareboundtocomplywiththeCEN/CENELECInternalRegulationswhichstipulatetheconditionsforgivingthisEurope an Standardthestatusofanationalstandardwithoutanyalteration.Uptoda

10、telistsandbibliographicalreferencesconcernings uchnational standardsmaybeobtainedonapplicationtotheCentralSecretariatortoanyCENmember. ThisEuropeanStandardexistsinthreeofficialversions(English,French,German).Aversioninanyotherlanguagemadebytra nslation undertheresponsibilityofaCENmemberintoitsownlan

11、guageandnotifiedtotheCentralSecretariathasthesamestatusast heofficial versions. CENmembersarethenationalstandardsbodiesofAustria,Belgium,Cyprus,CzechRepublic,Denmark,Estonia,Finland,France, Germany,Greece,Hungary,Iceland,Ireland,Italy,Latvia,Lithuania,Luxembourg,Malta,Netherlands,Norway,Poland,Portu

12、gal, Slovakia, Slovenia,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEANCOMMITTEEFORSTANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2005CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwideforCENnationalMembers. R

13、ef.No.EN14546:2005:EEN 14546:2005 (E) 2 Contents page Foreword 3 1 Scope .4 2 Normative references .4 3 Principle.4 4 Reagents4 5 Apparatus and equipment6 6 Procedure 6 7 Calculation.8 8 Precision8 9 Test report .9 Annex A (informative) Results of the inter-laboratory test10 Bibliography.12 EN 14546

14、:2005 (E) 3 Foreword This document (EN 14546:2005) 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 standard, either by publication of an identical text or

15、 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 are bound to implement this European Standard: Austr

16、ia, 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 and United Kingdom. EN 14546:2005 (E) 4 1 Scope This

17、European Standard specifies a method for the determination of total arsenic in foodstuffs by hydride generation atomic absorption spectrometry (HGAAS) after dry ashing. Specific foodstuffs for which European Standards exist are excluded from the scope of this horizontal European Standard. It is the

18、task of the analyst to review if vertical standards exist. 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 (in

19、cluding any amendments) applies. EN 13804, Foodstuffs Determination of trace elements Performance criteria, general considerations and sample preparation. 3 Principle The samples treated with nitric acid and ashing aid are evaporated to dryness and then mineralized at 425 C with a gradual increase i

20、n temperature. The ash is dissolved in hydrochloric acid and arsenic is quantified by HGAAS-procedure at the arsenic line at 193,7 nm 1. WARNING The use of this standard may involve hazardous materials, operations and equipment. This standard does not purport to address all the safety problems assoc

21、iated with its use. It is the responsibility of the user of this standard to establish appropriate health and safety practices and determine the applicability of regulatory limitations prior to use. 4 Reagents 4.1 General The concentration of arsenic in the reagents and water used shall be low enoug

22、h not to affect results of the determination. 4.2 Hydrochloric acid 4.2.1 Hydrochloric acid, not less than 30 % of approximately (HCl) = 1,15 g/ml. 4.2.2 Diluted hydrochloric acid, c ( 6 mol/l). Dilute 500 ml hydrochloric acid (4.2.1) with water in a proportion of 1+1 parts by volume. EN 14546:2005

23、(E) 5 4.3 Nitric acid, not less than 65 % (mass fraction) of approximately p (HNO 3 ) =1,4 g/ml. 4.3.1 Diluted nitric acid 1, w = 32 % 1)To be prepared by mixing mix nitric acid (4.3) and water in a proportion of 1 + 1 parts by volume. 4.3.2 Diluted nitric acid 2, w = 6,5 % 1)Mix nitric acid (4.3) a

24、nd water in a proportion of 1 + 9 parts by volume. 4.3.3 Diluted nitric acid 3, w = 3,3 % 1)Mix nitric acid (4.3) and water in a proportion of 1 + 19 parts by volume. 4.4 Magnesium oxide, w = not less than 90 % 1)4.5 Magnesium nitrate hexahydrate, w = not less than 98 % 1)4.6 Ashing aid Suspend 20 g

25、 of magnesium nitrate hexahydrate (4.5) and 2 g of magnesium oxide (4.4) in 100 ml of water. 4.7 Sodium hydroxide, w = not less than 95 % 1)4.8 Potassium iodide, w = not less than 99,5 % 1)4.9 Ascorbic acid, w =not less than 99,7 % 1)4.10 Pre-reducing solution Dissolve 5 g of potassium iodide (4.8)

26、and 5 g of ascorbic acid (4.9) in 100 ml of water. 4.11 Arsenic stock solution, in nitric acid, with a mass concentration (As (V)=1 000 mg/l The use of a stock solution accompanied by a certificate is advisable. 4.12 Arsenic calibration solutions 4.12.1 Intermediate standard solution Prepare a stand

27、ard of 25 g/l in HCl (4.2.2) from the stock solution (4.11) 4.12.2 Calibration standards Take an aliquot of the intermediate standard (e.g. 3 ml for a final concentration of 3 g/l) and make up to 5 ml with HCl (4.2.2). Add 5 ml of pre-reducing solution (4.10). Wait 30 min and make up to 25 ml with H

28、Cl (4.2.2). Following the same procedure prepare at least three calibration standards at different concentrations plus the zero point of the curve. The concentrations selected shall not exceed the linear range of the calibration curve of arsenic. 1) w is the mass fraction. EN 14546:2005 (E) 6 4.13 S

29、odium borohydride, w = not less than 96% 1)4.14 Sodium hydroxide, w = not less than 98% 1)4.15 Sodium borohydride solution The concentration of this reducing solution may vary according to the system of hydride generation employed and the recommendations given by the manufacturer in the manual for t

30、he equipment. Filter if necessary. This solution shall be prepared daily. 5 Apparatus and equipment 5.1 General To minimize the contamination, all apparatus which come into direct contact with the sample and the solutions shall be carefully pre-treated according to EN 13804. 5.2 Programmable muffle

31、furnace Equipped with a microprocessor or muffle furnace with thermostat. 5.3 Atomic absorption spectrometer Equipped with an electrically heated quartz cell and an accessory for hydride generation with or without flow injection. 5.4 Lamp for arsenic Hollow-cathode or electrodeless discharge lamp. 5

32、.5 Hot plate or sand bath With stepwise heating control. 6 Procedure 6.1 Pre-treatment Homogenise the sample in accordance with EN 13804. 6.2 Test portion Weigh an amount of 250 mg to 1000 mg dry sample or an equivalent quantity of fresh sample into a tall heat resistant glass beaker with a minimum

33、capacity of 200 ml. 6.3 Dry ashing 6.3.1 Ashing procedure Add 2,5 ml of ashing aid (4.6) per 250 mg of dry sample. In order to avoid precipitation add the ashing aid while shaking the suspension. Then add 5 ml of nitric acid (4.3.1) and evaporate in a sand bath (5.5) to a dry EN 14546:2005 (E) 7 res

34、idue. Increase the temperature gradually and slowly to avoid boiling, the production of foam, and splashing or spattering. Cover the glass beaker with a watch glass and place in the muffle furnace at an initial temperature not higher than 150 C. Increase the temperature to (425 25) C at a maximum ra

35、te of 50 C/h and maintain for 12 h. The rate of increase in temperature shall be maintained at the level recommended to avoid a loss of material. Take the crucible out of the furnace and let it cool. Repeat the ashing procedure until the sample is completely incinerated. For this purpose add 5 ml of

36、 nitric acid (4.3.2), evaporate in the sand bath, and place again the ashes in the muffle furnace, i.e. the ashes should be white/grey or slightly coloured (the number of repetitions necessary varies depending on the type of sample). 6.3.2 Dissolution of the sample ash Add 1 ml of water to wet the a

37、sh and then add 5 ml of hydrochloric acid (4.2.2) to the crucible, ensuring that all the ash comes into contact with the acid. Then add 5 ml of pre-reducing agent (4.10). Wait 30 min and make up to 25 ml with diluted hydrochloric acid (4.2.2). If necessary, filter the samples before diluting to volu

38、me. The filter shall be decontaminated by an initial washing with nitric acid (4.3.3) and two subsequent washings with deionized water. After filtering the samples and in order to avoid losses, wash the filter with hydrochloric acid (4.2.2) and add the washing liquids to the solution before diluting

39、 to volume, as above. Treat three reagent blanks in the same way as the samples. The sample solutions are stable for 24 h at 4 C. 6.4 Hydride generation atomic absorption spectrometry (HGAAS) 6.4.1 Spectrometer conditions Optimize the instrument in accordance with the recommendations described in th

40、e manual provided with the instrument. The readings shall be made at 193,7 nm. 6.4.2 Hydride generation technique 6.4.2.1 General Certain elements (e.g. Co, Cu, Cr, Fe, Mg, Ni, Sb, Sn and Se) may cause interference in hydride generation. This interference is limited, or eliminated, when the sample i

41、s diluted in diluted hydrochloric acid (4.2.2). If the sample requires further dilution, do so with diluted hydrochloric acid (4.2.2). Confirm that there are no matrix effects or inter-element interference by verifying that the differences between the slopes of the calibration curves and the standar

42、d addition curves are not significant. If the matrix effect persists, use the method of standard addition. 6.4.2.2 Standard addition method Determine the linear range of the standard calibration function. It is important that the measurements are made in the linear range when the method of standard

43、addition is used. A standard addition curve should consist of at least three points of which at least two are standard additions. The concentration of the highest standard should be 3 to 5 times the concentration in the sample solution. The concentration of the lower standard should be half of the h

44、ighest standard. Plot a graph of the absorbances obtained in this way against the added concentrations and extrapolate the resulting straight line until it intercepts the concentration axis. EN 14546:2005 (E) 8 7 Calculation Calculate the mass fraction, w, of total arsenic, in milligram per kilogram

45、 of the sample, using equation (1): 1000 = m F V a w (1) where a is the concentration of the element to be determined in the test solution used, in microgram per litre; V is the volume of the sample solution, in millilitre; F is the dilution factor, taking into account the pre-reduction and any furt

46、her dilutions in the case of high element concentrations; m is the initial sample mass, in gram. If the concentration in the blank solutions is below the limit of quantification of the method, it shall not be considered in the calculations. If necessary, subtract the concentration in the blank solut

47、ion from the concentration of the sample solution. 8 Precision 8.1 General Details of an inter-laboratory test are summarised in Annex A. The values derived from this inter-laboratory test may not be applicable to concentration ranges and matrices other than those given. 8.2 Repeatability The absolu

48、te difference between two independent single test results obtained with the same test method on identical test material in the same laboratory by the same operator using the same apparatus within a short time interval will exceed the repeatability limit r given in Table 1 in not more than 5 % of the cases. 8.3 Reproducibility The absolute difference between two single test results obtained with the same test method on identical test material in different laboratories by different operators using different equipment will