DIN EN 16159-2012 Animal feeding stuffs - Determination of selenium by hydride generation atomic absorption spectrometry (HGAAS) after microwave digestion (digestion with 65 % nitr.pdf

1、April 2012 Translation by DIN-Sprachendienst.English price group 11No part of this translation 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

2、65.120!$B“1885831www.din.deDDIN EN 16159Animal feeding stuffs Determination of selenium by hydride generation atomic absorptionspectrometry (HGAAS) after microwave digestion (digestion with 65 %nitric acid and 30 % hydrogen peroxide)English translation of DIN EN 16159:2012-04Futtermittel Bestimmung

3、von Selen mit Atomabsorptionsspektrometrie-Hydridtechnik (HD-AAS) nachMikrowellen-Druckaufschluss (Aufschluss mit 65 % Salpetersure und 30 %Wasserstoffperoxid)Englische bersetzung von DIN EN 16159:2012-04Aliments pour animaux Dosage du slnium par spectromtrie dabsorption atomique par gnration dhydru

4、res(SAAGH) aprs digestion par micro-ondes (extraction avec de lacide nitrique 65 % et duperoxyde dhydrogne 30 %)Traduction anglaise de DIN EN 16159:2012-04www.beuth.deDocument comprises 18 pagesIn case of doubt, the German-language original shall be considered authoritative.03.12 DIN EN 16159:2012-0

5、4 2 A comma is used as the decimal marker. National foreword This standard has been prepared by Technical Committee CEN/TC 327 “Animal feeding stuffs - Methods of sampling and analysis” (Secretariat: NEN, Netherlands) under a mandate. The responsible German body involved in its preparation was the N

6、ormenausschuss Lebensmittel und landwirtschaftliche Produkte (Food and Agricultural Products Standards Committee), Working Committee NA 057-03-03 AA Futtermittel. The method described in this standard is based upon a method developed by the Verband Deutscher Landwirtschaftlicher Untersuchungs- und F

7、orschungsanstalten (VDLUFA) (Association of German Agricultural Experimental and Research Stations) and verified by interlaboratory tests. The DIN Standards corresponding to the International Standards referred to in this document are as follows, whereby EN ISO Standards are only listed below if the

8、se have not been published as DIN EN ISO Standards with the same number: EN ISO 3696 DIN ISO 3696 National Annex NA (informative) Bibliography DIN ISO 3696, Water for analytical laboratory use Specification and test methods EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 16159 February 2012 ICS

9、 65.120 English Version Animal feeding stuffs - Determination of selenium by hydride generation atomic absorption spectrometry (HGAAS) after microwave digestion (digestion with 65 % nitric acid and 30 % hydrogen peroxide) Aliments pour animaux - Dosage du slnium par spectromtrie dabsorption atomique

10、 par gnration dhydrures (SAAGH) aprs digestion par micro-ondes (extraction avec de lacide nitrique 65 % et du peroxyde dhydrogne 30 %) Futtermittel - Bestimmung von Selen mit Atomabsorptionsspektrometrie-Hydridtechnik (HD-AAS) nach Mikrowellen-Druckaufschluss (Aufschluss mit 65 % Salpetersure und 30

11、 % Wasserstoffperoxid) This European Standard was approved by CEN on 30 December 2011. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists

12、 and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC 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 translation under t

13、he responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Ger

14、many, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE F

15、R NORMUNG Management Centre: Avenue Marnix 17, B-1000 Brussels 2012 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 16159:2012: EEN 16159:2012 (E) 2 Contents Page Foreword 31 Scope 42 Normative references 43 Principle 44 Reagents .

16、55 Apparatus and equipment 66 Procedure .76.1 General 76.2 Preparation of the test solution 76.3 Measurement of the test solution 86.3.1 Pre-dilution of the test solution 86.3.2 Pre-reduction of the (pre-diluted) test solution 86.3.3 Spectrometer settings of the flow-injection hydride generation ato

17、mic absorption spectrometer (HGAAS) 96.3.4 HGAAS determination .97 Calculation . 108 Precision 108.1 Introduction . 108.2 General . 118.3 Repeatability 118.4 Reproducibility 119 Test report . 11Annex A (informative) Results of the inter-laboratory test 12Annex B (informative) Flowchart - Determinati

18、on of selenium by hydride generation atomic absorption spectrometry (HGAAS) after microwave digestion (digestion with 65 % nitric acid and 30 % hydrogen peroxide . 13Annex C (informative) Alternative digestion procedure with the same digestion efficiency: Acid digestion with a mixture of 65 % nitric

19、 acid and 70 % perchloric acid (7:3 by volume) at atmospheric pressure 14C.1 Preparation of selenium calibration solutions 14C.2 Preparation of the test solution . 14C.3 Measurement of the test solution . 15C.4 Ten rules for automated wet ashing with perchloric acid 15Bibliography . 16DIN EN 16159:2

20、012-04 EN 16159:2012 (E) 3 Foreword This document (EN 16159:2012) has been prepared by Technical Committee CEN/TC 327 “Animal feeding stuffs”, the secretariat of which is held by NEN. This European Standard shall be given the status of a national standard, either by publication of an identical text

21、or by endorsement, at the latest by August 2012, and conflicting national standards shall be withdrawn at the latest by August 2012. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible

22、for identifying any or all such patent rights. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound

23、 to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, 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, Sw

24、eden, Switzerland, Turkey and the United Kingdom. DIN EN 16159:2012-04 EN 16159:2012 (E) 4 1 Scope This European Standard specifies a method for the determination of selenium in animal feeding stuffs by hydride generation atomic absorption spectrometry (HGAAS) after microwave pressure digestion. The

25、 method was successfully tested by an inter-laboratory study of CEN/TC 327/WG 4 in the range of 0,25 mg/kg to 74 mg/kg. The limit of quantification is 0,5 g/l of the test solution which corresponds to the calibration standard 2. Using a test portion of 0,5 g and a volume of the test solution of 25 m

26、l after pressure digestion the limit of quantification is calculated as 0,125 mg/kg in the feed material. NOTE A lower limit of quantification could be achieved each laboratory has to prove it. 2 Normative references The following documents, in whole or in part, are normatively referenced in this do

27、cument and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN ISO 3696, Water for analytical laboratory use Specification and test methods (ISO 3696)

28、 EN ISO 6497, Animal feeding stuffs Sampling (ISO 6497) prEN ISO 6498, Animal feeding stuffs Guidelines for sample preparation (ISO/DIS 6498) 3 Principle Selenium is determined in the test solution by hydride generation atomic absorption spectrometry (fluorescence hydride generation atomic absorptio

29、n) after microwave pressure digestion and a pre-reduction step. The homogenised feeding stuff test sample is digested by nitric acid and hydrogen peroxide under pressure and high temperatures in a microwave-heated pressure digestion system. Selenium ions of the test solution are reduced with hydroch

30、loric acid to selenium (IV) and converted to selenium hydride (SeH2) by sodium borohydride. This selenium hydride is transferred by a gas stream to a heated measurement cell and decomposed. The absorption at the selenium line at 196,0 nm corresponds to the amount of selenium. NOTE Selenium (VI) is n

31、ot determined by the hydridisation as described here. It is therefore necessary to adjust the digestion conditions and to exercise a pre-reduction step with hydrochloric acid to yield only selenium (IV). Other digestion procedures with the same digestion efficiency or other measurement systems like

32、Fl-HGAAS or hydride generation inductively coupled plasma optical emission spectrometry are possible (see Annex C). WARNING The use of this standard can involve hazardous materials, operations and equipment. This standard does not purport to address all the safety problems associated with its use. I

33、t is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. DIN EN 16159:2012-04EN 16159:2012 (E) 5 4 Reagents The concentration of the trace elements in the reagents and water used

34、shall be low enough not to affect the results of the determination. A blank should be measured simultaneously with the test samples on each day of the analysis to control contamination and carry over with selenium in the reagents and apparatus used. Use only water of quality 2 as described in EN ISO

35、 3696. NOTE High purity is essential to avoid potential contamination. Therefore, only use reagents available with high purity or perform an extraction by a sub-boiling distillation for nitric acid (4.1). 4.1 Nitric acid, not less than 65 % (mass fraction), of approximately (HNO3) = 1,4 g/ml. 4.2 Di

36、luted nitric acid, mix 100 ml nitric acid (4.1) with water to 1 l. 4.3 Hydrogen peroxide, not less than 30 % (mass fraction), of approximately (H2O2) 1,1 g/ml. 4.4 Hydrochloric acid, 30 %, mass concentration of approximately (HCl) = 1,15 g/ml. 4.5 Diluted hydrochloric acid, e.g. about 3 % (mass frac

37、tion), as carrier solution for the use in the flow-injection-procedure. EXAMPLE Dilute approximately 90 ml of hydrochloric acid (4.4) to 1 l with water. 4.6 Sodium borohydride solution, e.g. c = 2 g/l. Dissolve 2 g of sodium hydroxide pellets in water, add 2 g of sodium borohydride and dilute to 1 0

38、00 ml with water into 1 000 ml flask (5.3). Prepare a fresh solution daily and, when necessary, filter before use. When the analysis procedure takes longer, it is recommended to cool the sodium borohydride solution, i.e. with ice around the flask, during its use in the HGAAS measurement. NOTE 1 The

39、concentration by mass of the sodium borohydride solution may vary with the system and the instructions of the relevant manufacturer shall therefore be observed. NOTE 2 Sodium borohydride, stable aq. solution, 4,4 mol/l in 14 mol/l NaOH is also commercially available. WARNING It is essential to obser

40、ve the safety instructions for working with sodium borohydride. Sodium borohydride forms hydrogen with acids and this can result in an explosive air/hydrogen mixture. A permanent extraction system shall be provided at the point where measurements are carried out. 4.7 Selenium stock solution, c (Se)

41、= 1 000 mg/l. The stock solution is commercially available. It is advisable to use certified stock solutions. Otherwise, dissolve 1,4053 g of selenium dioxide (SeO2) and 2 g sodium hydroxide in approximately 50 ml water, and dilute to 1 000 ml with water. 4.8 Selenium standard solution, c (Se) = 1 m

42、g/l. Dilute e.g. 100 l of the stock solution (4.7) in a 100 ml flask (5.3) to give a concentration of 1 mg/l. The selenium standard solution shall contain an adequate amount of hydrochloric acid, e.g. 2 ml of hydrochloric acid (4.4) per 100 ml. NOTE The standard solution is stable for at least three

43、 months. 4.9 Selenium calibration solutions. DIN EN 16159:2012-04 EN 16159:2012 (E) 6 For the preparation of five calibration solutions, the following procedure is recommended: Take aliquots of 0 l, 50 l, 250 l, 500 l and 1 000 l of the selenium standard solution (4.8) into 100 ml flasks (5.3). Afte

44、r the addition of 20 ml of nitric acid (4.2) and 10 ml of hydrochloric acid (4.4) the calibration solutions are heated for 20 min in a water bath at 80 C (see pre-reduction step 6.3.2). After cooling down to room temperature, the flasks (5.3) are made up to the mark with water and the calibration so

45、lutions are measured. The selenium concentrations of the calibration solutions are: 0 g/l; 0,5 g/l; 2,5 g/l; 5 g/l and 10 g/l (see Table 1). Table 1 Recommended calibration solutions (4.9) for the determination of selenium Selenium (Se) Concentration of calibration solution (4.9) after pre-reduction

46、 procedure g/l Aliquot of selenium standard solution (4.8) transferred in 100 ml flasks (5.3) (pre-reduction step) l Calibration standard 1 0 0 Calibration standard 2 0,5 50 Calibration standard 3 2,5 250 Calibration standard 4 5 500 Calibration standard 5 10 1 000 Choose the concentrations of the c

47、alibration solutions so as not to exceed the linear range of the calibration function. It is recommended to use a minimum of five calibration solutions with different concentrations. The calibration solutions are measured from the lowest to the highest concentration. In general, the calibration curv

48、e should be linear. Using a non-linear calibration function is possible if it is well described. NOTE Prepare fresh calibration solutions (inclusive pre-reduction step) on the day of the analysis. 5 Apparatus and equipment To minimise the contamination, all apparatus which come into direct contact with the sample and the solutions should be carefully pre-treated according to EN 138