BS EN 15505-2008 Foodstuffs - Determination of trace elements - Determination of sodium and magnesium by flame atomic absorption spectrometry (AAS) after microwave digestion《食品 痕量元.pdf

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1、BRITISH STANDARDBS EN 15505:2008Foodstuffs Determination of trace elements Determination of sodium and magnesium by flame atomic absorption spectrometry (AAS) after microwave digestionICS 67.050g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38

2、g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN 15505:2008This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 March 2008 BSI 2008ISBN 978 0 580 56731 5National forewordThis British Standard i

3、s the UK implementation of EN 15505:2008.The UK participation in its preparation was entrusted to Technical Committee AW/-/3, Food analysis Horizontal methods.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to includ

4、e all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations. Amendments/corrigenda issued since publicationDate CommentsEUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN 15505March 20

5、08ICS 67.050English VersionFoodstuffs - Determination of trace elements - Determination ofsodium and magnesium by flame atomic absorptionspectrometry (AAS) after microwave digestionProduits alimentaires - Dosage des lments traces -Dosage du sodium et du magnsium par spectromtriedabsorption atomique

6、de flamme aprs digestion parmicro-ondesLebensmittel - Bestimmung von Elementspuren -Bestimmung von Natrium und Magnesium mit Flammen-Atomabsorptionsspektrometrie (AAS) nachMikrowellenaufschlussThis European Standard was approved by CEN on 7 February 2008.CEN members are bound to comply with the CEN/

7、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 be obtained on application to the CEN Management Centre or to a

8、ny 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 Management Centre has the same status as theofficial versions.CE

9、N 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, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Swed

10、en, 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 and by any means reservedworldwide for CEN national Members.Ref.

11、 No. EN 15505:2008: EEN 15505:2008 (E) 2 Contents Page Foreword3 1 Scope 4 2 Normative references 4 3 Principle4 4 Reagents.4 5 Apparatus and equipment 6 6 Procedure .6 7 Calculation7 8 Precision.7 9 Test report 8 Annex A (informative) Results of the inter-laboratory tests .9 Annex B (informative) A

12、dditional information on calcium.12 Bibliography 15 BS EN 15505:2008EN 15505:2008 (E) 3 Foreword This document (EN 15505:2008) 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 given the

13、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 document may be

14、 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: Austria, Be

15、lgium, 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. BS EN 15505:2008

16、EN 15505:2008 (E) 4 1 Scope This document specifies methods for the determination of sodium and magnesium in foodstuffs by flame atomic absorption spectrometry (AAS) after microwave digestion. Collaborative studies have been carried out (Annex A). The method is suitable for the determination of sodi

17、um not less than 1 500 mg/kg and magnesium not less than 250 mg/kg. Data for calcium is included for information (Annex B). The method is not applicable to wheat bran. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated referenc

18、es, 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 EN 13805, Foodstuffs Determination of

19、 trace elements Pressure digestion 3 Principle The samples are digested in closed vessels in a microwave oven in a mixture of nitric acid and hydrogen peroxide. The resulting solution is diluted with water, and the sodium and magnesium contents are determined by flame-AAS using matrix modifiers. WAR

20、NING 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 safety and health practices and determine

21、 the applicability of regulatory limitations prior to use. 4 Reagents 4.1 General Use only reagents and water, which shall have an element level low enough not to affect results. The use of certified stock solutions is advisable. 4.2 Nitric acid 4.2.1 Nitric acid, not less than 65 % of approximately

22、 mass concentration (HNO3) = 1,4 g/ml. In case of insufficient purity, it is necessary to purify the nitric acid in a distillation apparatus as described in EN 13805. 4.2.2 Diluted nitric acid solution 1, mass fraction w = 2,7 % Dilute 42 ml nitric acid (4.2.1) to 1 000 ml with water. 4.2.3 Diluted

23、nitric acid solution 2, mass fraction w = 0,65 % Mix nitric acid (4.2.1) and water in a proportion minimum of 1 + 99 parts by volume. BS EN 15505:2008EN 15505:2008 (E) 5 4.3 Hydrochloric acid, mass fraction w = 37 % 4.4 Hydrogen peroxide, mass fraction w = 30 % 4.5 Cesium chloride solution (CsCl), f

24、or use in AAS analysis Dissolve 31,75 g of cesium chloride in water and dilute to 250 ml. The solution will be stable in a refrigerator for at least 6 months. 4.6 Lanthanum(III)oxide (La2O3) solution, for use in AAS analysis, 5 % (weight/volume) Weigh 14,66 g of lanthanum(III)oxide into a 250 ml bea

25、ker, moisten with 10 ml of water and add 62,5 ml of HCl (4.3). Transfer to a 250 ml volumetric flask and fill up with water. The solution will be stable in a refrigerator for one month. 4.7 Sodium solution 4.7.1 Sodium stock solution, mass concentration (Na) = 1 000 mg/l 4.7.2 Sodium standard soluti

26、on, mass concentration (Na) = 10 mg/l Dilute 1 ml of sodium stock solution (4.7.1) to 100 ml in a volumetric flask with 2,7 % nitric acid (4.2.2). The solution will remain stable for one month at room temperature. 4.8 Magnesium solution 4.8.1 Magnesium stock solution, mass concentration (Mg) = 1 000

27、 mg/l 4.8.2 Magnesium standard solution, mass concentration (Mg) = 10 mg/l Dilute 1 ml of magnesium stock solution (4.8.1) to 100 ml in a volumetric flask with 0,65 % nitric acid (4.2.3). The solution will remain stable for one month at room temperature. BS EN 15505:2008EN 15505:2008 (E) 6 5 Apparat

28、us and equipment 5.1 General All glassware and plastic ware should be carefully cleaned and rinsed according to the procedure in EN 13804. 5.2 Laboratory microwave oven Check the microwave oven for delivered power according to the procedure in EN 13804. 5.3 Atomic absorption spectrometer 5.4 Element

29、 specific lamps For sodium and magnesium element specific lamps with wavelength of 589,0 nm and 285,2 nm respectively will apply. 5.5 Acetylene Use acetylene of appropriate quality. 5.6 Air 6 Procedure 6.1 Pre-treatment Homogenise the sample in accordance with the recommendations in EN 13804. If nec

30、essary, dry the sample in a way that does not affect the element contents, e.g. by freeze drying. 6.2 Sample preparation Use the test solution obtained by microwave oven digestion method according to EN 13805 for the determination of sodium and magnesium. 6.3 Dilution Pipette a suitable volume of th

31、e sample solution, add 5 % La-solution (4.6) and dilute this volume with 0,65 % nitric acid (4.2.3) so that the final concentration of Mg is within the linear range of measurement of the elements. In this example, the following ranges are selected for the standard curves; for Mg, 0,05 mg/l to 0,4 mg

32、/l. The lowest point may be lower, if required by the concentrations of the sample solutions. Add 5 % of La-solution (4.6) to a final mass fraction of La of 1 % (e.g. 2 ml 5 % is diluted to 10 ml). Pipette a suitable volume of the sample solution, add 1 ml of Cs-solution (4.5) and dilute this volume

33、 with 2,7 % nitric acid (4.2.2) so that the final concentration of Na is within the range of measurement of the element. In this example, the following range is selected for the standard curve: 0,1 mg/l to 1,0 mg/l. The lowest point may be lower required by concentration of the sample solution. BS E

34、N 15505:2008EN 15505:2008 (E) 7 6.4 Preparation of standard solution Prepare working standard solutions for Na of 0,1 mg/l, 0,25 mg/l, 0,5 mg/l, 0,75 mg/l and 1,0 mg/l from the Na standard solution (4.7.2). Add 0,5 ml, 1,25 ml, 2,5 ml, 3,75 ml and 5 ml to separate 50 ml volumetric flasks, add 1 ml o

35、f Cs-solution (4.5) and dilute to the mark with diluted nitric acid solution 1 (4.2.2). Prepare fresh solution daily. Prepare working standard solutions for Mg of 0,05 mg/l, 0,1 mg/l, 0,2 mg/l and 0,4 mg/l from the Mg standard solution (4.8.2). Add 0,25 ml, 0,5 ml, 1,0 ml and 2,0 ml to separate 50 m

36、l volumetric flasks, add 10 ml of 5 % La-solution (4.6) and dilute to the mark with diluted nitric acid solution 2 (4.2.3). Prepare fresh solutions daily. 6.5 Settings for the atomic absorption spectrometer Before every determination, adjust the instrument as specified in the manufacturers operating

37、 manual. Example of instrument parameters for sodium and magnesium may be 589,0 nm and 285,2 nm (wavelength) and 0,2 nm and 0,7 nm (slit), respectively. 7 Calculation Calculate the element content, w, as mass fraction of sodium and magnesium in milligram per kilogram of the sample, using the followi

38、ng equation: mFVaw= (1) where a is the content of the element in the test solution, in milligram per litre; V is the volume of the digestion solution after being made up, in millilitres; F is the dilution factor of the test solution; m is the initial sample mass, in grams. If necessary, subtract the

39、 concentration in the blank solution from the concentration of the sample solution, before the calculation is made. 8 Precision 8.1 General Details of an inter-laboratory trial on the precision of the method are summarized in Annex A. The values derived from this inter-laboratory test may not be app

40、licable to concentration ranges and matrices other than those given. 8.2 Repeatability and reproducibility Repeatability is the absolute difference between two independent single test results (blind duplicate), obtained with the same method on identical test material in the same laboratory by the sa

41、me operator using the same equipment within a short interval of time. This will in not more than 5 % of the cases exceed the values of r given in Table 1 to Table 2. Reproducibility is the absolute difference between two single test results, obtained with the same method on identical test material i

42、n different laboratories by different operators using different equipment. This will in not more than 5 % of the cases exceed the values of R given in Table 1 to Table 2. BS EN 15505:2008EN 15505:2008 (E) 8 Table 1 Mean values, repeatability limits and reproducibility limits for sodium Sample x mg/k

43、g r mg/kg R mg/kg Broccoli 2 290 210 320 Carrot 3 54 330 420 White bread 8 260 570 1 040 Saithe fillet 2 030 210 350 Pork 1 48 77 280 Cheese 5 380 980 1 040 Table 2 Mean values, repeatability limits and reproducibility limits for magnesium Sample x mg/kg r mg/kg R mg/kg Simulated diet (D) 665 70 129

44、 Simulated diet (F) 618 76 120 Milk powder, freeze dried 859 51 111 Minced fish, freeze dried 749 50 144 Apple, dried 251 15 32 Chocolate cake, dried 284 16 32 9 Test report The test report shall specify: a) all information necessary for the complete identification of the sample; b) test method used

45、, with reference to this document; c) test results obtained and the units in which they are specified; d) date when the analysis was finished; e) whether the requirement of the repeatability limit has been fulfilled; f) all operating details not specified in this document or regarded as optional, to

46、gether with details of any incidents occurred when performing the method which may have influenced the test results. BS EN 15505:2008EN 15505:2008 (E) 9 Annex A (informative) Results of the inter-laboratory tests The precision of the method was established by The Nordic Committee on Food Analysis (N

47、MKL) in inter-laboratory tests evaluated in accordance with 1. The test for sodium was carried out in 2003 and the test for magnesium was carried out in 1995. The results are given in Table A.1 to Table A.3. Nine laboratories participated in an inter-laboratory method-performance (collaborative) stu

48、dy of a method for the determination of sodium in foodstuffs by flame atomic absorption spectrometry (AAS) after wet digestion using a microwave oven technique 2. The method was tested on a total of six materials (broccoli, carrot, bread, saithe fillet, pork and cheese) ranging in sodium content fro

49、m 1 480 mg/kg to 8 260 mg/kg. The materials were presented to the participants in the study as blind duplicates and the participants carried out single determinations on each sample. The highest RSDRvalue was found for sample of cheese, the only wet sample in the study. Table A.1 Statistical results for sodium in the freeze dried test samples Sample Parameter Broccoli Carrot White bread Saithe fillet Pork Cheese*Number of laboratories 9 9 9 9 9 9 Number of laboratories after elimination of outliers 9 9 9 9 8 7 Number of outliers 0 0 0 0 1 2 M