BS ISO 5738-2004 Milk and milk products - Determination of copper content - Photometric method - (Reference method)《乳和乳制品 铜含量的测定 光度参照法》.pdf

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1、BRITISH STANDARD BS ISO 5738:2004 Milk and milk products Determination of copper content Photometric method (Reference method) ICS 67.100.01 BS ISO 5738:2004 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 24 September 2004 BSI 24 September 2

2、004 ISBN 0 580 44473 2 National foreword This British Standard reproduces verbatim ISO 5738:2004 and implements it as the UK national standard. It supersedes BS 6394-1:1983 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee AW/5, Milk and milk products,

3、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 publications referred to in this document may be found in the BSI Catalogue under the section entit

4、led “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 contract. Users are responsible for its correct application. Compliance

5、 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 proposals for change, and keep the UK interests informed; monitor related inte

6、rnational and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to v, a blank page, pages 1 to 11 and a back cover. The BSI copyright notice displayed in this document indicates when the do

7、cument was last issued. Amendments issued since publication Amd. No. Date Comments Reference numbers ISO 5738:2004(E) IDF 76:2004(E) OSI DI dnaF 4002INTERNATIONAL STANDARD ISO 5738 IDF 76 Second edition 2004-09-01 Milk and milk products Determination of copper content Photometric method (Reference m

8、ethod) Lait et produits laitiers Dtermination de la teneur en cuivre Mthode photomtrique (Mthode de rfrence) BSISO5738:2004IS:8375 O4002(E) ID:67 F4002(E) DPlcsid Fremia ihTs PDF file may ctnoian emdebt dedyfepcaes. In ccaocnadrw eith Aebods licensilop gnic,y this file mairp eb ynted iv roweb detu s

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11、is suitlbae fosu re yb ISO memdob rebeis dna IDF antilano ocmmittees. In the unlikely veent that a problem relating to it is f,dnuo lpsaei enfomr tI ehStneC Olar Secrteiraat ta the serddas igleb nevow. ISO dna ID4002 F All irthgs erse.devr lnUeto sswrehise specified, on trap fo this lbupictaion maeb

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14、04IS:8375 O4002(E) ID:67 F4002(E) I SO dna ID 4002 F All irhgts seredevr iiiContents Page Foreword iv Foreword. v 1 Scope 1 2 Normative references . 1 3 Terms and definitions. 1 4 Principle . 2 5 Reagents 2 6 Apparatus. 3 7 Sampling 4 8 Procedure. 4 8.1 Preparation of test sample. 4 8.2 Weighing and

15、 pretreatment of the test portion 6 8.3 Digestion 7 8.4 Colour development . 7 8.5 Blank test . 8 8.6 Photometric measurements. 8 8.7 Number of determinations . 8 8.8 Calibration curve. 8 9 Calculation and expression of results 8 9.1 Calculation. 8 9.2 Expression of results 9 10 Precision 9 10.1 Int

16、erlaboratory test . 9 10.2 Repeatability 9 10.3 Reproducibility 9 11 Test report 9 Annex A (informative) Results of interlaboratory test 10 Bibliography . 11 BSISO5738:2004IS:8375 O4002(E) ID:67 F4002(E) iv I SO dna ID 4002 F All irhgts seredevrForeword ISO (the International Organization for Standa

17、rdization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right t

18、o be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Sta

19、ndards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an In

20、ternational Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 5738

21、 IDF 76 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC International. It is being published jointly by ISO and IDF and separately by AOAC International. This edition of

22、ISO 5738 IDF 76 cancels and replaces the first edition of ISO 5738 (ISO 5738:1980), which has been technically revised. BSISO5738:2004ISO 5738:2004(E) ID:67 F4002(E) I SO dna ID 4002 F All irhgts seredevr vForeword IDF (the International Dairy Federation) is a worldwide federation of the dairy secto

23、r with a National Committee in every member country. Every National Committee has the right to be represented on the IDF Standing Committees carrying out the technical work. IDF collaborates with ISO and AOAC International in the development of standard methods of analysis and sampling for milk and

24、milk products. Draft International Standards adopted by the Action Teams and Standing Committees are circulated to the National Committees for voting. Publication as an International Standard requires approval by at least 50 % of the National Committees casting a vote. ISO 5738 IDF 76 was prepared b

25、y Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with AOAC International. It is being published jointly by ISO and IDF and separately by AOAC International. All work was carried out by Joint ISO/

26、IDF/AOAC Action Team on Minor compounds, of the Standing Committee on Minor components and characterization of physical properties, under the aegis of its project leader, Dr G. Ellen (NL). This edition of ISO 5738 IDF 76 cancels and replaces the first edition of IDF 76 (IDF 76A:1980), which has been

27、 technically revised. BSISO5738:2004NITERNATNOIAL STANDARD IS:8375 O4002(E) ID:67 F4002(E)I SO dna ID 4002 F All irhgts seredevr 1Milk and milk products Determination of copper content Photometric method (Reference method) 1 Scope This International Standard specifies a reference method for the dete

28、rmination of the copper content of milk and milk products. The method is applicable to a) milk, skimmed milk and buttermilk, b) evaporated milk and sweetened condensed milk, c) whole and skimmed milk powder, d) cream and butter, e) butterfat, f) ice-cream, g) hard, semi-hard and soft cheeses of vari

29、ous ages, and processed cheese, and h) caseins, caseinates and coprecipitates. The method is suitable for determining copper contents as low as 0,05 mg/kg in test samples of butter and butterfat. NOTE See IDF 68 for details of butterfat. 2 Normative references The following referenced documents are

30、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 (including any amendments) applies. ISO 648:1977, Laboratory glassware One-mark pipettes ISO 835-1:1981, Laboratory glasswar

31、e Graduated pipettes Part 1: General requirements 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 copper content mass fraction of substances determined by the procedure described in this International Standard NOTE The copper content is expre

32、ssed as milligrams per kilogram. BSISO5738:2004IS:8375 O4002(E) ID:67 F4002(E) 2 I SO dna ID 4002 F All irhgts seredevr4 Principle The organic material in the test sample is digested with a mixture of nitric and sulfuric acids (preceded in the case of cream, butter and butterfat by removal of the fa

33、t). The solution is neutralized with ammonia solution followed by complexing the copper as a salt of diethyl dithiocarbamic acid. The copper(II) salt is extracted with amyl acetate. The absorbance of the yellow solution is measured photometrically. The presence of bismuth and/or tellurium interferes

34、 with the determination of copper. See the check for absence and the method of removal specified in 8.6. 5 Reagents All reagents shall be of analytical grade and, with the exception of the copper(ll) sulfate standard solutions (5.12), shall be free from copper. 5.1 Water, double distilled, with the

35、final distillation being carried out in a copper-free distillation unit. 5.2 Ethanol (CH 3 CH 2 OH), with a volume fraction of about 96 %. Distil the ethanol, if necessary, in a copper-free distillation unit. 5.3 Diethyl ether C 2 H 5 ) 2 O Distil the diethyl ether, if necessary, in a copper-free di

36、stillation unit. 5.4 Light petroleum (petroleum ether), with boiling range between 40 C and 60 C. Distil the light petroleum, if necessary, in a copper-free distillation unit. 5.5 Nitric acid, concentrated, 20 (HNO 3 ) = 1,42 g/ml. Distil in a copper-free distillation unit. Discard the first 50 ml.

37、5.6 Sulfuric acid 5.6.1 Sulfuric acid, concentrated, 20 (H 2 SO 4 ) = 1,84 g/ml. 5.6.2 Sulfuric acid, dilute, c(H 2 SO 4 ) = 0,5 mol/l). 5.7 Hydrogen peroxide solution, 20 (H 2 O 2 ) = 1,099 g/ml to 1,103 g/ml. 5.8 Ammonia solution, concentrated, 20 (NH 3 ) = 0,91 g/ml. Purify the ammonia solution,

38、if necessary, by vacuum distillation in a copper-free distillation unit. 5.9 Citrate/EDTA solution Dissolve 400 g of ammonium citrate (NH 4 ) 3 C 6 H 5 O 7 and 100 g of EDTA disodium salt dihydrate (ethylenedinitrilo)-tetraacetic acid disodium salt dihydrate (Na 2 C 10 H 14 N 2 O 8 2H 2 O) in water

39、(5.1) in a 1 000 ml one-mark volumetric flask (6.12). Dilute to the mark with water. Purify the citrate/EDTA solution, if necessary, as follows. Add three drops of phenolphthalein solution (5.13) to the citrate/EDTA solution. Then add sufficient ammonia solution (5.8) until the solution remains pale

40、 pink. Add 10 mg of sodium diethyl dithiocarbamate (5.10). Warm the solution in a water bath (6.5) set at 60 C for about 10 min to completely dissolve the sodium diethyl dithiocarbamate. Cool to ambient temperature. BSISO5738:2004IS:8375 O4002(E) ID:67 F4002(E) I SO dna ID 4002 F All irhgts seredevr

41、 3Extract the solution in a 2 l separation funnel five times with 15 ml of amyl acetate (5.11). Repeat the whole purification procedure until the last 15 ml portion of amyl acetate remains colourless. 5.10 Sodium diethyl dithiocarbamate solution (C 2 H 5 ) 2 NCSSNa Dissolve 400 mg of sodium diethyl

42、dithiocarbamate trihydrate C 2 H 5 ) 2 NCSSNa 3H 2 O in 90 ml of water (5.1) in a 100 ml one-mark volumetric flask (6.12). Dilute to the mark with ammonia solution (5.8). Store the solution in the dark in a refrigerator at between 0 C and 8 C. Renew the solution every week. 5.11 Amyl acetate Dry 1 l

43、 of amyl acetate on 15 g of anhydrous sodium sulfate for 24 h. Distil in a copper-free distillation unit. Collect the fraction distilled at between 136 C and 140 C. Instead of amyl acetate, xylene distilled in a copper-free distillation unit may be used. 5.12 Copper(ll) sulfate standard solutions 5.

44、12.1 Copper stock solution Dissolve 196,5 mg of copper(ll) sulfate pentahydrate (CuSO 4 5H 2 O) in an amount of water in a 1 000 ml one- mark volumetric flask (6.12). Carefully add 5 ml of dilute sulfuric acid (5.6.2) and mix. Dilute to the mark with water (5.1). 5.12.2 Copper working solution Prepa

45、re this solution on the day of use. Use a one-mark pipette (6.11) to add 10 ml of copper stock solution (5.12.1) to 5 ml of dilute sulfuric acid (5.6.2) previously added to a 500 ml one-mark volumetric flask (6.12) and mix. Dilute to the mark with water. NOTE 1 ml of the copper working solution cont

46、ains 1 g of Cu. 5.13 Phenolphthalein solution Dissolve 1 g of phenolphthalein in 100 ml of 90 % ethanol (volume fraction). 5.14 Potassium cyanide solution (KCN), with a mass fraction of 5 % KCN. WARNING Take safety precautions as KCN is poisonous. It is the responsibility of the user of this standar

47、d to establish safety and health practices and to determine the applicability of regulatory limitations prior to use. 5.15 Sodium hydroxide solution, c(NaOH) = 1 mol/l. 6 Apparatus 6.1 Glassware Keep the clean glassware in 10 % nitric acid (mass fraction). Before use, rinse three times with distille

48、d water and then three times with double-distilled water. Dry, if necessary, by successively rinsing with ethanol and diethyl ether. 6.2 Analytical balance, capable of weighing to the nearest 1 mg, with a readability of 0,1 mg. 6.3 Appropriate grinding or grating device. BSISO5738:2004IS:8375 O4002(

49、E) ID:67 F4002(E) 4 I SO dna ID 4002 F All irhgts seredevr6.4 Sieve, made of copper-free material, with nominal size of aperture 0,5 mm. 6.5 Water baths, capable of operating at 20 C 2 C, at 40 C 1 C, at 45 C 1 C, at 60 C 1 C, at between 30 C and 40 C, at between 40 C and 60 C, at between 60 C and 65 C and at between 80 C and 90 C. 6.6 Micro gas burner. 6.7 Digestion flasks, (Kjeldahl