BS ISO 14378-2009 Milk and dried milk - Determination of iodide content - Method using high-performance liquid chromatography《乳品和干乳品 碘化物含量的测定 高效液相色谱法》.pdf

1、BS ISO14378:2009ICS 67.100.10NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDMilk and dried milk Determinationof iodide content Method using high-performance liquidchromatographyThis British Standard was published under the authority of the Standards Policy and

2、Strategy Committee on 30November 2009 BSI 2009ISBN 978 0 580 67131 9Amendments/corrigenda issued since publicationDate CommentsBS ISO 14378:2009National forewordThis British Standard is the UK implementation of ISO 14378:2009. Itsupersedes BS ISO 14378:2000 which is withdrawn.The UK participation in

3、 its preparation was entrusted to TechnicalCommittee AW/5, Chemical analysis of milk and milk products.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are re

4、sponsible for its correct application. Compliance with a British Standard cannot confer immunityfrom legal obligations.BS ISO 14378:2009Reference numbersISO 14378:2009(E)IDF 167:2009(E)ISO and IDF 2009INTERNATIONAL STANDARD ISO14378IDF167Second edition2009-10-01Milk and dried milk Determination of i

5、odide content Method using high-performance liquid chromatography Lait et lait en poudre Dtermination de la teneur en iodure Mthode par chromatographie en phase liquide haute performance BS ISO 14378:2009ISO 14378:2009(E) IDF 167:2009(E) PDF disclaimer This PDF file may contain embedded typefaces. I

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9、CTED DOCUMENT ISO and IDF 2009 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO or IDF at the respectiv

10、e address below. ISO copyright office International Dairy Federation Case postale 56 CH-1211 Geneva 20 Diamant Building Boulevard Auguste Reyers 80 B-1030 Brussels Tel. + 41 22 749 01 11 Tel. + 32 2 733 98 88 Fax + 41 22 749 09 47 Fax + 32 2 733 04 13 E-mail copyrightiso.org E-mail infofil-idf.org W

11、eb www.iso.org Web www.fil-idf.org Published in Switzerland ii ISO and IDF 2009 All rights reservedBS ISO 14378:2009ISO 14378:2009(E) IDF 167:2009(E) ISO and IDF 2009 All rights reserved iiiForeword ISO (the International Organization for Standardization) is a worldwide federation of national standa

12、rds 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 to be represented on that committee. International organ

13、izations, 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 Standards are drafted in accordance with the rules given i

14、n 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 International Standard requires approval by at least 75 %

15、 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 14378IDF 167 was prepared by Technical Committee ISO/TC 34,

16、 Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF). It is being published jointly by ISO and IDF. This second edition of ISO 14378IDF 167 cancels and replaces the first edition (ISO 14378:2000), of which it constitutes a minor revision. BS ISO 143

17、78:2009ISO 14378:2009(E) IDF 167:2009(E) iv ISO and IDF 2009 All rights reservedForeword IDF (the International Dairy Federation) is a non-profit organization representing the dairy sector worldwide. IDF membership comprises National Committees in every member country as well as regional dairy assoc

18、iations having signed a formal agreement on cooperation with IDF. All members of IDF have the right to be represented on the IDF Standing Committees carrying out the technical work. IDF collaborates with ISO in the development of standard methods of analysis and sampling for milk and milk products.

19、The main task of Standing Committees is to prepare International Standards. 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 IDF N

20、ational Committees casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. IDF shall not be held responsible for identifying any or all such patent rights. ISO 14378IDF 167 was prepared by the International Dairy Federatio

21、n (IDF) and Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products. It is being published jointly by IDF and ISO. All work was carried out by the former Joint ISO-IDF Group of Experts (E15 Heavy metals and other elements) which is now part of the Joint ISO-IDF Action

22、 Team on Minor compounds of the Standing Committee on Minor components and characterization of physical properties. This edition of ISO 14378IDF 167 cancels and replaces IDF 167:1994, of which it constitutes a minor revision. BS ISO 14378:2009INTERNATIONAL STANDARD ISO 14378:2009(E)IDF 167:2009(E) I

23、SO and IDF 2009 All rights reserved 1Milk and dried milk Determination of iodide content Method using high-performance liquid chromatography WARNING The use of this International Standard may involve hazardous materials, operations and equipment. Persons using this International Standard should be f

24、amiliar with normal laboratory practice. This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish health and safety practices and determine the applicability of regulatory limitations prior to use. 1 Scop

25、e This International Standard specifies a high-performance liquid chromatographic (HPLC) method for the determination of the iodide content of pasteurized whole milk and dried skimmed milk, when present at levels from 0,03 g/g to 1 g/g and 0,3 g/g to 10,0 g/g, respectively. NOTE 1 The method has bee

26、n collaboratively studied with samples of liquid whole milk and dried skimmed milk. There are no reasons to expect that the method does not apply to skimmed or partially skimmed milk as well as to dried whole milk. NOTE 2 The method measures free (ionic) iodide. However, the total iodide content of

27、fresh milk and good quality milk powder, in which no microbial growth has occurred, may contain a mass fraction of 5 % to 10 % of organically bound iodide. More iodide can be bound organically in milk where microbiological deterioration has occurred. 2 Normative references The following referenced d

28、ocuments are 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 3696, Water for analytical laboratory use Specification and test method

29、s 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 iodide content of pasteurized whole milk iodide content of dried skimmed milk mass fraction of substances determined by the procedure specified in this International Standard NOTE The iodide c

30、ontent is conventionally expressed in micrograms per gram. BS ISO 14378:2009ISO 14378:2009(E) IDF 167:2009(E) 2 ISO and IDF 2009 All rights reserved4 Principle A test portion is diluted with water. Insoluble and high-molecular-mass material is removed by filtration through a 25 000 D cut-off membran

31、e. Iodide ions are separated by reverse-phase ion-pair HPLC with an electrochemical detector and a silver working electrode at 0 mV to 50 mV. The iodide content is calculated by means of a calibration graph. 5 Reagents Use only reagents of recognized analytical grade or, if appropriate, of special H

32、PLC grade. 5.1 Water, complying with ISO 3696, grade 2. 5.2 Iodide standard solutions. WARNING Protect aqueous solutions of iodides from light as they are unstable when exposed to visible frequencies. 5.2.1 Iodide stock solution, corresponding to 100 mg of iodide per litre. Dissolve 130,8 mg of pota

33、ssium iodide (KI) in water in a 1 000 ml one-mark volumetric flask (6.2). Dilute to the mark with water and mix. The iodide stock solution may be kept for 1 month if stored in the dark at room temperature. 5.2.2 Iodide working standard solutions, corresponding to 20 g, 50 g, 150 g and 250 g of iodid

34、e per litre, respectively. Pipette 20 l, 50 l, 150 l and 250 l of the iodide stock solution (5.2.1) into four separate 100 ml one-mark volumetric flasks (6.2). Dilute each solution to the mark with water and mix. The iodide working standard solutions may be kept for 1 week if stored in the dark at r

35、oom temperature. 5.3 Acetonitrile (CH3CN), HPLC grade. 5.4 Hexadecyltrimethylammonium chloride solution CH3(CH2)15N(CH3)3Cl, 25 % (by mass) solution in water, ion-pair chromatography grade. 5.5 HPLC eluent: mixture of disodium hydrogenphosphate and hexadecyltrimethylammonium chloride in a mixture of

36、 acetonitrile and water (68 + 32 by volume), pH = 6,8. Dissolve 1,42 g of disodium hydrogenphosphate (Na2HPO4) in about 600 ml of water in a 1 000 ml one-mark volumetric flask (6.2). Add 1,3 ml of hexadecyltrimethylammonium chloride solution (5.4) and mix well. Then add 320 ml of acetonitrile (5.3)

37、and mix again. Adjust the pH to 6,8 with concentrated orthophosphoric acid (H3PO4). Dilute to the mark with water and mix well. Clarify the solution by filtering first through a 1,2 m membrane filter and then through a 0,5 m membrane filter. Swirl the solution to mix it and simultaneously degas by m

38、eans of a vacuum or sonification for 2 min before initial use. The eluent can be modified by the addition of small amounts of water or acetonitrile to achieve minor adjustments in the retention time of iodide. The eluent may be kept for 1 year, if stored in a tightly closed container. 5.6 n-Pentanol

39、. BS ISO 14378:2009ISO 14378:2009(E) IDF 167:2009(E) ISO and IDF 2009 All rights reserved 36 Apparatus Usual laboratory equipment and, in particular, the following. 6.1 Analytical balance, capable of weighing to the nearest 0,01 g, with a readability of three decimal places. 6.2 One-mark volumetric

40、flasks, of capacities 100 ml and 1 000 ml, ISO 10423class A. 6.3 Micropipettes, capable of delivering 20 l, 50 l, 150 l and 250 l respectively, ISO 8655-26. 6.4 Graduated pipette, of capacity 2 ml, with 0,1 ml graduations, ISO 8352class A or class AS. 6.5 Measuring cylinder, of capacity 500 ml, ISO

41、47884class A. 6.6 pH-meter, with combined glass electrode. 6.7 Membrane filters, 1,2 m and 0,5 m, nylon-6-6, or equivalent, with filter equipment to clarify HPLC eluent. 6.8 Centrifuge, capable of holding 50 ml centrifuge tubes and capable of producing a radial acceleration of 1 000g. 6.9 Centrifuge

42、 tubes, of capacity 50 ml, internal diameter 27 mm, conical, made of disposable plastic, with screw caps. 6.10 Conical membrane supports, to support membrane filter cone (6.11) in centrifuge tubes (6.9) Amicon CS1A1), or equivalent. 6.11 Membrane filter cones, 25 000 D to 30 000 D cut-off Amicon Cen

43、treflo CF-251), or equivalent. Prepare new membrane filter cones before use as follows. Soak in a mixture of ethanol and water (2 + 8 parts by volume) for 1 h. Remove the cone and drain. Mount it in a conical membrane support (6.10) and place it in a 50 ml centrifuge tube. Centrifuge the cone at a r

44、adial acceleration of 900g to 1 000g for 5 min to 10 min. Invert the new membrane filter cone to drain any remaining solvent. Place the prepared cones into supports in clean, labelled centrifuge tubes (6.9) for sample analysis. After each use, soak the cones immediately in hot water, flush well with

45、 hot water and store them in a mixture of ethanol and water (1 + 5 parts by volume). Remove the solvent before the next use of the cones as described above for new cones. Alternatively, Millipore Ultrafre-PF 1)(UFP1, 10 000 D cut-off) filtration units may be used. These disposable filters do not nee

46、d any pretreatment, and filtering can be carried out by slight pressure or vacuum; no centrifuge is needed. 6.12 HPLC equipment, consisting of the following. 6.12.1 Pump, capable of delivering a volume flow rate of 2 ml/min. 6.12.2 Injector, manual or automatic, with injection capacities of 50 l to

47、200 l. 6.12.3 Analytical column, Partisphere C-181), 5 m, internal diameter 4,7 mm, length 110 mm, or equivalent. 1) Example of a suitable product available commercially. This information is given for the convenience of users of this International Standard, and does not constitute an endorsement by

48、ISO or IDF of this product. Equivalent products may be used if they can be shown to produce comparable results. BS ISO 14378:2009ISO 14378:2009(E) IDF 167:2009(E) 4 ISO and IDF 2009 All rights reserved6.12.4 Guard column (optional), Spheri-5 C-181)cartridge, internal diameter 3,2 mm, length 15 mm, o

49、r equivalent. 6.12.5 Electrochemical detector, to be used in the d.c. mode or pulsed amperometric mode, with a silver working electrode at 0 mV to + 50 mV potential. 6.12.6 Strip chart recorder or integrator, capable of peak area measurement, preferably using an electronic integrator having so-called “negative peak” function Spectra Physics1)is suitable. 7 Sampling Sampling is not part of the method specified in this International Standard. A recommended sampling method is given in IS