BS EN 13805-2014 Foodstuffs Determination of trace elements Pressure digestion《食品 痕量元素测定 加压分解》.pdf

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1、BSI Standards PublicationBS EN 13805:2014Foodstuffs Determinationof trace elements PressuredigestionBS EN 13805:2014 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN 13805:2014. Itsupersedes BS EN 13805:2002 which is withdrawn.The UK participation in its preparat

2、ion was entrusted to TechnicalCommittee AW/275, Food analysis - Horizontal methods.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its co

3、rrectapplication. The British Standards Institution 2014. Published by BSI StandardsLimited 2014ISBN 978 0 580 79939 6ICS 67.050Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy

4、Committee on 31 October 2014.Amendments issued since publicationDate Text affectedBS EN 13805:2014EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 13805 October 2014 ICS 67.050 Supersedes EN 13805:2002English Version Foodstuffs - Determination of trace elements - Pressure digestion Produits alim

5、entaires - Dosage des lments traces - Digestion sous pression Lebensmittel - Bestimmung von Elementspuren - Druckaufschluss This European Standard was approved by CEN on 9 August 2014. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving

6、 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 CEN-CENELEC Management Centre or to any CEN member. This European Standard exists in three offici

7、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 CEN-CENELEC Management Centre has the same status as the official versions. CEN members are the national standards bodies of A

8、ustria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sw

9、eden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2014 CEN All rights of exploitation in any form and by any means reserved worldwide for

10、CEN national Members. Ref. No. EN 13805:2014 EBS EN 13805:2014EN 13805:2014 (E) 2 Contents Page Foreword 3 1 Scope 4 2 Normative references 4 3 Principle 4 4 Reagents .4 5 Apparatus and equipment 5 5.1 General 5 5.2 Pressure digestion apparatus 5 5.2.1 General 5 5.2.2 Pressure digestion apparatus wi

11、th conventional heating .5 5.2.3 Pressure digestion apparatus with microwave-assisted heating .5 5.2.4 Pressure digestion autoclave with microwave-assisted heating .5 5.3 Ultrasonic bath with heating device 6 5.4 Subboiling distillation apparatus, 6 5.5 Stripping apparatus, 6 6 Procedure .6 6.1 Gene

12、ral 6 6.2 Sample preparation .6 6.3 Pressure digestion conditions .6 6.3.1 Sample 6 6.3.2 Acid addition 7 6.3.3 Digestion temperature .7 6.3.4 Digestion time 8 6.3.5 Cooling 8 6.3.6 Treatment of the digestion 8 6.3.7 Quality control of the analysis .8 6.4 Example of pressure digestions 8 6.4.1 Examp

13、le of a high-pressure ashing digestion with conventional heating 8 6.4.2 Example of a microwave digestion 9 6.4.3 Example of a digestion in a microwave-heated autoclave 9 Annex A (normative) Figures of apparatus . 10 Bibliography . 12 BS EN 13805:2014EN 13805:2014 (E) 3 Foreword This document (EN 13

14、805:2014) 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 by endorsement, at the latest by April 2

15、015 and conflicting national standards shall be withdrawn at the latest by April 2015. 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 for identifying any or all such patent rights.

16、 This document supersedes EN 13805:2002. The changes between this edition and the previous one are as follows: a) restructuring of some clauses; b) 5.2.2, “Pressure digestion apparatus with conventional heating“ was added; c) 5.2.3, “Pressure digestion apparatus with microwave-assisted heating“ was

17、added; d) 5.2.4, “Pressure digestion autoclave with microwave-assisted heating“ was added; e) 6.3.2, “Acid addition“ was revised” f) 6.4, “Example of pressure digestions“ was completely revised and completed; g) bibliographic referenced were added; h) the whole document was editorially revised. Acco

18、rding to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany

19、, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. BS EN 13805:2014EN 13805:2014 (E) 4 1 Scope This European Standard specifies a method for t

20、he pressure digestion of foodstuffs intended for the determination of elements. This method has been collaboratively tested in combination with atomic absorption (flame, electrothermal (ET), hydride, cold-vapour) techniques and ICP-MS. Other techniques such as e.g. ICP-OES, voltammetry or atomic flu

21、orescence can be used in combination with this European Standard. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references,

22、the latest edition of the referenced document (including any amendments) applies. EN 13804, Foodstuffs - Determination of elements and their chemical species - General considerations and specific requirements 3 Principle The method is a physicochemical pressure digestion method used to mineralize th

23、e sample material and to prepare a measurement solution containing elements to be determined. The method described here is applied when the measurement has been validated in combination with this digestion method and reference is made to this European Standard. This procedure will relate to the tota

24、l element content depending on reagents and determination procedures used. The sample is homogenized avoiding contamination. Afterwards it is digested with nitric acid (sometimes with addition of other acids), at high temperatures and pressure in a closed vessel, applying conventional or microwave-a

25、ssisted heating 1, 2, 3. 4 Reagents The concentration of the trace elements in reagents and water used shall be low enough to not affect the results of the determination. In the case of insufficient purity, it is necessary to purify nitric acid and hydrochloric acid in a distillation apparatus (see

26、5.4 and Figure A.1). 4.1 Nitric acid, mass fraction w of not less than 65 % and density of approximately (HNO3) = 1,4 g/ml. 4.2 Diluted nitric acid, mix nitric acid (4.1) and water in a proportion of at least (1 + 9) parts by volume. 4.3 Hydrochloric acid, w not less than 30 % and approximately (HCl

27、) = 1,15 g/ml. 4.4 Hydrofluoric acid, w not less than 40 % and approximately (HF) = 1,14 g/ml. 4.5 Hydrogen peroxide, w not less than 30 % and approximately (H2O2) = 1,11 g/ml. BS EN 13805:2014EN 13805:2014 (E) 5 5 Apparatus and equipment 5.1 General To minimize contamination, carefully clean all th

28、ose apparatus coming into contact with the sample by treating it with diluted nitric acid (4.2) and afterwards with water. In addition, a stripping apparatus (Figure A.2) can be used for cleaning vessels or bottles. 5.2 Pressure digestion apparatus 5.2.1 General Commercially available safety-tested

29、pressure vessels made of acid-resistant materials and comprising inserts of acid-resistant, low-contamination materials are used to accommodate the sample material. The pressure vessels shall be able to withstand a temperature of at least 180 C as well as be stably operated at this temperature. Ensu

30、re safe operation during the whole digestion process by suitable safety devices (e.g. bursting discs, pressure shell, power control). 5.2.2 Pressure digestion apparatus with conventional heating Apparatus working with or without external autoclave pressure and designed for various working pressures

31、should be used. Inserts of polytetrafluoroethylene (PTFE), quartz glass, perfluoroethylenepropylene (FEP) 4, 5 or perfluoroalkoxy (PFA) can be used. If digestion temperatures exceed 230 C, the use of quartz glass is advantageous. For the determination of mercury and other elements, which are adsorbe

32、d easily on rough surfaces (e.g. antimony), quartz glass is recommended. 5.2.3 Pressure digestion apparatus with microwave-assisted heating Systems with microwave-assisted heating shall be equipped with a temperature-measuring device. The temperature of the digestion solution can be measured interna

33、lly and/or externally 6. Reliable temperature measurement values are obtained, e.g. via sensors introduced into the pressure vessel. When using an infrared sensor for measuring the vessel temperature, it shall be ensured through consultation with the manufacturer that the displayed temperature corre

34、sponds to the temperature of the solution in the pressure vessel. Do not use systems with microwave-assisted heating without a temperature-measuring device. Inserts made of fluorinated plastics such as PTFE, advanced PFA or perfluoropropylvinylether-modified PTFE (e.g. TFM) as well as quartz glass c

35、an be used. If digestion temperatures exceed 230 C the use of quartz glass is advantageous. For the determination of mercury and other elements, which are adsorbed easily on rough surfaces (e.g. antimony), quartz glass is recommended. 5.2.4 Pressure digestion autoclave with microwave-assisted heatin

36、g Alternatively to the apparatus described under 5.2.2 and 5.2.3, systems with a microwave heated autoclave can be used. The microwave energy is coupled into the absorption liquid and thus the digestion vessels are heated. The digestion vessels are sealed with an autoclave filling pressure of at lea

37、st 40 bar (= 40 x 105Pa). Digestion vessels made of fluorinated plastics (PTFE and derivates) or of quartz glass are recommended. BS EN 13805:2014EN 13805:2014 (E) 6 If digestion temperatures exceed 230 C, the use of quartz glass is advantageous. For the determination of mercury and other elements,

38、which are adsorbed easily on rough surfaces (e.g. antimony), quartz glass is recommended. 5.3 Ultrasonic bath with heating device 5.4 Subboiling distillation apparatus, made of quartz glass or a similar material of high-purity fluoropolymers, according to Figure A.1, for distilling acids at temperat

39、ures below their boiling point. 5.5 Stripping apparatus, according to Figure A.2, for cleaning vessels or bottles with hot acid vapour. Only vessels or bottles made of fluorinated plastics (PTFE and its derivates), of quartz glass or glass are stable during the stripping procedure. 6 Procedure 6.1 G

40、eneral WARNING The application of this standard can involve the use of dangerous substances, operations and equipment. This standard does not purport, however, to address all the safety problems associated with its use. It is the responsibility of the user of this standard to establish the appropria

41、te safety and health measures, which comply with applicable and current regulations. During each step of the method, contamination shall be as low as possible. It shall be borne in mind that the digestion of carbon-rich materials (e.g. cellulose, carbohydrates, fats, oils) can result in explosions.

42、Alcohol shall be evaporated since its contact with concentrated nitric acid results in delayed violent reactions. Perchloric acid shall not be used for pressure digestion. Before the pressure digestion apparatus is used, read operating manual and safety instructions carefully. Particular attention s

43、hall be paid to the risk to the laboratory staff posed by nitrogen oxides. 6.2 Sample preparation Prepare the samples using normal household practices. Avoid as far as possible any contamination with the elements to be determined (e.g. when determining chromium and nickel, no stainless steel equipme

44、nt shall be used for the sample preparation), see EN 13804. The sample preparation shall ensure homogeneous starting material for the test portion. 6.3 Pressure digestion conditions 6.3.1 Sample Adapt the sample weight to the capacity of the digestion vessel and the maximum permissible pressure incr

45、ease; in doing so, do not deviate from the manufacturers information for safety reasons. The maximum sample weight depends on the samples carbon content and water content. In the case of carbon-rich samples, such as fats and carbohydrate rich foodstuffs, a maximum of 200 mg (to the nearest milligram

46、) of fresh mass can as a rule be digested 5. If the carbon content is lower, the mass of the sample may be increased up to 3 g of fresh mass or 4 ml of liquid. Depending on the volume of the digestion vessels, other sample weights may be used; but the ratio of sample mass to acid volume (6.3.2), how

47、ever, shall not be changed. BS EN 13805:2014EN 13805:2014 (E) 7 In the case of samples in powder form with a weight of approximately 200 mg, add 1 ml of water and mix thoroughly in order to obtain a sample that is well suspended in the water. Take care to ensure that mixing does not result in splash

48、ing losses or in damage to the digestion vessels. In the case of materials that cannot be mixed with water, for example fatty materials, do not add water. With alcoholic samples it is imperative that the alcohol is completely removed after transferring the sample into the digestion vessel, by gentle

49、 heating, e.g. in the heatable ultrasonic bath (5.3), at 60 C, and before the adding the acid. In doing so, it shall be ensured that there are no losses of the elements to be determined. 6.3.2 Acid addition WARNING Samples which absorb microwave energy and are not fully covered by the acid, can result in local overheating of the digestion vessel, resulting in local melting, followed by bursting of the vessel. WARNING Perchloric acid shall never be used in pressure digestions, not even in small amounts. The volume of acid required for the digestio