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1、BRITISH STANDARD BS EN 13805:2002 Foodstuffs Determination of trace elements Pressure digestion The European Standard EN 13805:2002 has the status of a British Standard ICS 67.050 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Licensed Copy: sheffieldun sheffieldun, na, Mon O
2、ct 30 01:53:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 13805:2002 This British Standard, having been prepared under the direction of the Consumer Products and Services Sector Policy and Strategy Committee, was published under the authority of the Standards Policy and Strategy Committee on 1
3、2 April 2002 BSI 12 April 2002 ISBN 0 580 39489 1 National foreword This British Standard is the official English language version of EN 13805:2002. The UK participation in its preparation was entrusted to Technical Committee AW/-/3, Horizontal analysis, which has the responsibility to: A list of or
4、ganizations 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 this document may be found in the BSI Standards Catalogue under the section entitled “International Stan
5、dards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Stand
6、ard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments
7、 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 9 and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No.
8、 DateComments Licensed Copy: sheffieldun sheffieldun, na, Mon Oct 30 01:53:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 13805 March 2002 ICS 67.050 English version Foodstuffs - Determination of trace elements - Pressure digestion Produits aliment
9、aires - Dtermination des lments-traces - Digestion sous forte pression Lebensmittel - Bestimmung von Elementspuren - Druckaufschluss This European Standard was approved by CEN on 22 February 2002. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the condition
10、s for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Management Centre or to any CEN member. This European Standard exists in three offici
11、al versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belg
12、ium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Ce
13、ntre: rue de Stassart, 36 B-1050 Brussels 2002 CENAll rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 13805:2002 E Licensed Copy: sheffieldun sheffieldun, na, Mon Oct 30 01:53:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 13805:2002 (E)
14、 2 Contents page Foreword3 1Scope 3 2Normative references 3 3Principle3 4Reagents.3 5Apparatus and equipment.4 6Sampling.4 7Procedure .4 Annex A (normative) Figures of the apparatus7 Bibliography9 Licensed Copy: sheffieldun sheffieldun, na, Mon Oct 30 01:53:10 GMT+00:00 2006, Uncontrolled Copy, (c)
15、BSI EN 13805:2002 (E) 3 Foreword This document (EN 13805:2002) has been prepared by Technical Committee CEN/TC 275 “Food analysis Hori- zontal 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 ident
16、ical text or by endorsement, at the latest by September 2002, and conflicting national standards shall be withdrawn at the lat- est by September 2002. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following coun- tries are bound to implement this Euro
17、pean Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Swe- den, Switzerland and the United Kingdom. Annex A is normative. 1 Scope This European Standard specifies a method for the
18、digestion of foodstuffs under pressure intended for use in the determination of trace elements. This method has been collaboratively tested in combination with atomic absorption (flame, furnace, hydride, cold-vapour) techniques, ICP-MS. ICP-OES and voltametry can be used in combination with the meas
19、urement standards, which make reference to this one. 2 Normative references This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text, and the publications are listed hereafter. Fo
20、r dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies (including amendments). EN 13804, Foodstuffs
21、Determination of trace elements Performance criteria, general considerations and sample preparation. 3 Principle Pressure digestion, physicochemical method described in this document for mineralising the sample material and for preparing a test solution containing the trace elements prior to their d
22、etermination according to the standards that make reference to this one and have been validated in combination with it. Apparatus with a low level of contamination is used to homogenise the sample, which is then digested in a sealed vessel in a pressure container at high temperature and pressure by
23、conventional or microwave assisted heating 1, 2, 3. 4 Reagents 4.1 General The concentration of the trace elements in the chemicals and water used shall be low enough not to affect the re- sults of the determination. Licensed Copy: sheffieldun sheffieldun, na, Mon Oct 30 01:53:10 GMT+00:00 2006, Unc
24、ontrolled Copy, (c) BSI EN 13805:2002 (E) 4 4.2 Nitric acid, not less than 65 %, (mass fraction), having a density of approximately ? (HNO3) = 1,4 g/ml. In case of insufficient purity it is necessary to purify the acid in a distillation apparatus (5.5). 4.3 Diluted nitric acid, to be prepared by mix
25、ing nitric acid (4.2) and water in a proportion minimum of 1 + 9 parts by volume. 4.4 Hydrochloric acid, not less than 30 %, (mass fraction), having a density of approximately ? (HCl) = 1,15 g/ml. 4.5 Hydrogen peroxide, not less than 30 %, (mass fraction). 5 Apparatus and equipment 5.1 General To mi
26、nimise the contamination, carefully clean all the apparatus which comes into direct contact with the sample by treatment with diluted nitric acid (4.3) and then with water. It is advisable to use a stripping apparatus (5.6) for cleaning vessels or flasks. 5.2 Pressure digestion apparatus, commercial
27、ly obtainable, tested safety pressure vessels made of acid- resistant materials and having holders for the sample of acid-resistant material with low level of contamination. Apparatus is available which uses a high-pressure incinerator with or without ambient autoclave pressure. Instead of polytetra
28、fluoroethylene (PTFE) holders, it is better to use graduated quartz holders, perfluoro ethylene propylene (FEP) holders 4, 5 or perfluoro alkoxy (PFA) holders. Quartz is advisable to be used for the mercury determination and for decomposition temperatures above 230 C. 5.3 Heating device, temperature
29、-controllable (e.g. heating block or microwave oven) 5.4 Ultrasonic bath 5.5 Distillation apparatus, quartz glass or equivalent made of high purity fluoropolymers, according to Figure A.1. 5.6 Stripping apparatus, according to Figure A.2. 6 Sampling Proceed according to prEN 13804. 7 Procedure 7.1 G
30、eneral At every stage in the method, steps shall be taken to ensure that contamination is as low as possible. WARNING The use of this European Standard can involve hazardous materials, operations and equip- ment. This standard does not purport to address all the safety problems associated with its u
31、se. It is the responsibility of the user of this European Standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. It shall be borne in mind that the digestion of carbon-rich materials (e.g. carbohydrates, fats etc.) can re
32、sult in ex- plosions. Licensed Copy: sheffieldun sheffieldun, na, Mon Oct 30 01:53:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 13805:2002 (E) 5 Before the pressure digestion apparatus is used, read operating manual and observe safety instructions. Pay par- ticular attention to the risk to the l
33、aboratory staff posed by nitrous gases. Detailed descriptions of the procedure shall be available in every laboratory in the form of working instructions. 7.2 Sample preparation Prepare the samples in a way as usual for the preparation of foodstuffs in the normal household. Avoid contamina- tion wit
34、h elements to be determined to the greatest possible extent (e.g. for the determination of chromium and nickel stainless steel knives shall not be used during the sample preparation). See prEN 13804. 7.3 Pressure digestion conditions 7.3.1 Initial sample mass and acid volumes Match the initial sampl
35、e mass to the capacity of the digestion vessel, with the manufacturers instructions being strictly observed for safety reasons. If the capacity is e.g. 70 ml, up to 400 mg (to the nearest milligram) of dry matter or up to 4 ml of liquid, equivalent to a carbon content of 200 mg 5, can as a rule be d
36、igested. If the carbon content is lower, the test portion may be in- creased. The volume of acid necessary for the digestion will depend on the nature of the sample material. Usually 3 ml of nitric acid will be sufficient to digest the amounts mentioned above. For pure fat, it may be necessary to re
37、duce the initial sample weight and to increase the amount of acid. 0,5 ml to 1 ml hydrogen peroxide may be added to pre- vent cementing of the sample on the wall of the digestion vessel and to achieve complete mixing of the sample with the acid. NOTEIf iron is subsequently to be determined, it can b
38、e necessary to add 0,5 ml of hydrochloric acid (4.4) to prevent losses due to adsorption on the vessel wall. 7.3.2 Digestion temperature Determine the necessary digestion temperature and consequently the completeness of the digestion, by the measur- ing method subsequently used (e.g. higher temperat
39、ures result in lower values of residual carbon in the digestion so- lutions. Thereby the background in ET-AAS and ICP-AES measurements is reduced. Interferences in the chromium determination by ICP-MS are minimised 6 and trouble free voltametric measurements can be done). A smooth rise in temperatur
40、e at the beginning of the digestion is advantageous. NOTEIn general, it applies that the quality of the digestion will become better with increasing digestion temperature, 7, 8. If it is likely that organic arsenic compounds are present in the food, a temperature of 320 C can be necessary, if HG-AAS
41、 is used for subsequent determination of arsenic 9. 7.3.3 Digestion time A suggested digestion time for homogenised sample material is about 3 h. In case of microwave systems digestion time is typically 15 min to 30 min. For some samples the digestion will be gentler if a preliminary reaction is all
42、owed to take place at room temperature, e.g. overnight, after adding the acid. 7.3.4 Cooling To reduce the pressure inside the digestion vessel, cool the still sealed pressure vessel to near the ambient tem- perature. 7.3.5 Preparation of test solution After the digestion vessel has been cooled and
43、opened, initially place it under a fume hood until brown fumes are no longer visible. It is highly recommended to degas the digestion solution in an ultrasonic bath. Fill up to a speci- fied volume with water (test solution) and transfer the test solutions to vessels made of quartz (highly recom- me
44、nded for mercury determinations), FEP or PFA. Licensed Copy: sheffieldun sheffieldun, na, Mon Oct 30 01:53:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 13805:2002 (E) 6 The digestion solution shall be clear and its volume roughly the same as before digestion. A marked reduction in volume indicat
45、es that the pressure vessel was not leak-tight and in such cases, the digestion shall be repeated. 7.3.6 Blank solution To check for contamination, prepare a reagent blank containing the same amount of acids as in the sample and up to 4 ml of water (depending on the initial sample weight), then carr
46、y out all the steps of the method (7.3.1 to 7.3.5). 7.3.7 Reference samples For the purpose of analytical control, analyse reference samples having reliably known contents of the elements to be determined, in parallel with all the series of samples analysed, the reference samples being subjected to
47、all the steps of the method, starting from digestion. 7.4 Example of microwave digestion When using 70 ml to 100 ml vessels, weigh 1 g to 2 g of meat or 3 g of lettuce (fresh weight). Add 3 ml of nitric acid and 0,5 ml of hydrogen peroxide, seal the digestion vessel and the pressure holders in the c
48、orrect manner. Apply low microwave energy at the beginning of the digestion and slowly raise the energy to the maximum power, e.g. start with 100 W, raise up to 600 W within 5 min, hold for 5 min, raise to 1000 W, hold for 10 min, cool down for minimum 20 min to 25 min. 7.5 Example of a high pressur
49、e asher digestion When using a 70 ml vessel, weigh 1 g to 2 g of meat or 3 g of lettuce (fresh weight). Add 3 ml of nitric acid, seal the digestion vessel and the pressure vessel in the correct manner and heat from room temperature to 150 C in 60 min, then to 300 C in 40 min and keep 300 C for 90 min before cooling down. Licensed Copy: sheffieldun sheffieldun, na, Mon Oct 30 01:53:10 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 13805:2002 (E) 7 Annex A (normative) Figures of the apparatus Key 1Distillation chamber 2Quartz glass tube 3Heat