1、BSI Standards PublicationBS ISO 20649:2015Infant formula and adultnutritionals Determinationof chromium, selenium andmolybdenum Inductivelycoupled plasma massspectrometry (ICP-MS)BS ISO 20649:2015 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 20649:2015.The U
2、K participation in its preparation was entrusted to Technical Committee AW/5, Chemical analysis of milk and milk products.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a c
3、ontract. Users are responsible for its correct application. The British Standards Institution 2015. Published by BSI Standards Limited 2015ISBN 978 0 580 90426 4 ICS 67.050 Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under the
4、authority of the Standards Policy and Strategy Committee on 30 November 2015.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e dBS ISO 20649:2015Infant formula and adult nutritionals Determination of chromium, selenium and molybdenum Inductively coupled plasma mass spectrometr
5、y (ICP-MS)Formules infantiles et produits nutritionnels pour adultes Dtermination de la teneur en chrome, slnium et molybdne Spectromtrie de masse avec plasma couplage inductif (ICP-SM)INTERNATIONAL STANDARDFirst edition2015-11-01Reference numbersISO 20649:2015(E)IDF 235:2015(E)ISO20649IDF235 ISO an
6、d IDF 2015BS ISO 20649:2015ISO 20649:2015(E)IDF 235:2015(E)ii ISO and IDF 2015 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO and IDF 2015, Published in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or
7、 by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright office International Dairy
8、FederationCh. de Blandonnet 8 CP 401 Silver Building Bd Auguste Reyers 70/B B-1030 BrusselsCH-1214 Vernier, Geneva, SwitzerlandTel. +41 22 749 01 11 Tel. + 32 2 325 67 40Fax +41 22 749 09 47 Fax + 32 2 325 67 41copyrightiso.org infofil-idf.orgwww.iso.org www.fil-idf.orgBS ISO 20649:2015ISO 20649:201
9、5(E)IDF 235:2015(E)Forewords .iv1 Scope . 12 Principle 13 Reagents and materials . 14 Apparatus . 25 Procedure. 25.1 Sample preparation 25.2 Preparation of the test solution 35.3 Determination . 36 Calculation 47 Method validation . 47.1 Linearity 47.2 Limit of quantification (LOQ) . 57.3 Matrix mat
10、ching with methanol. 57.4 Effects of easily ionizable elements (EIEs) . 57.5 Specificity 57.6 Accuracy 57.7 Precision . 57.8 Ruggedness and robustness 57.9 Reproducibility . 6Annex A (informative) Precision data . 7Bibliography 8 ISO and IDF 2015 All rights reserved iiiContents PageBS ISO 20649:2015
11、ISO 20649:2015(E)ForewordsISO (the International Organization for Standardization) 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 subj
12、ect for which a technical committee has been established has the right to 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 (IE
13、C) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be n
14、oted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).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 identifyin
15、g any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).Any trade name used in this document is information given for the convenience o
16、f users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supple
17、mentary informationThe committee responsible for this document is 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 INTERNATIO
18、NAL. The method described in this International Standard is equivalent to the AOAC Official Method 2011.19: Chromium, selenium, and molybdenum in infant formula and adult nutritional products, inductively coupled plasma-mass spectrometry.IDF 235:2015(E)iv ISO and IDF 2015 All rights reservedBS ISO 2
19、0649:2015ISO 20649:2015(E)IDF (the International Dairy Federation) is a non-profit private sector organization representing the interests of various stakeholders in dairying at the global level. IDF members are organized in National Committees, which are national associations composed of representat
20、ives of dairy-related national interest groups including dairy farmers, dairy processing industry, dairy suppliers, academics and governments/food control authorities.ISO and IDF collaborate closely on all matters of standardization relating to methods of analysis and sampling for milk and milk prod
21、ucts. Since 2001, ISO and IDF jointly publish their International Standards using the logos and reference numbers of both organizations.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 identify
22、ing any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).Any trade name used in this document is information given for the convenience
23、 of users and does not constitute and endorsement.ISO 20649 | IDF 235 was prepared by the IDF Standing Committee on Analytical Methods for Composition and the ISO Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, in collaboration with AOAC INTERNATIONAL. It is
24、being published jointly by ISO and IDF, and separately by AOAC INTERNATIONAL. The method described in this International Standard is equivalent to the AOAC Official Method 2011.19: Chromium, selenium, and molybdenum in infant formula and adult nutritional products, inductively coupled plasma-mass sp
25、ectrometry.All work was carried out by the ISO-IDF Project Group C38 of the Standing Committee on Analytical Methods for Composition under the aegis of its project leader, Mr Erik Konings (CH).IDF 235:2015(E) ISO and IDF 2015 All rights reserved vBS ISO 20649:2015BS ISO 20649:2015Infant formula and
26、adult nutritionals Determination of chromium, selenium and molybdenum Inductively coupled plasma mass spectrometry (ICP-MS)WARNING The use of this International Standard can involve hazardous materials, operations and equipment. This International Standard does not purport to address all the safety
27、problems associated with its use. It is the responsibility of the user of this International Standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.1 ScopeThis International Standard specifies a method for the quantitative
28、 determination of chromium, selenium and molybdenum in infant formula and adult nutritional formula.1The method has been validated in an interlaboratory study on seven different matrices.2 PrincipleA test portion is heated with nitric acid in a closed vessel microwave digestion system at 200 C. The
29、digested test solution, or an appropriate dilution, is presented to the inductively coupled plasma-mass spectrometer (ICP-MS) instrument standardized with acid matched standard calibrant solutions. An ionization buffer (potassium) is used to minimize easily ionizable element (EIE) effects, methanol
30、is added to normalize the carbon content, and germanium and tellurium are used as internal standards. It is permissible to combine the analysis of Cr/Mo/Se with simultaneous determination of any or all of these elements: Na, K, P, Mg, Ca, Fe, Zn, Cu, Mn. An ionization buffer would not be added if th
31、e calibration standards already contained Na, K, Mg, and/or Ca.3 Reagents and materialsDuring the analysis, unless otherwise stated, use only reagents of recognized analytical grade and distilled or demineralized water or water of equivalent purity. Equivalent chemicals and reagents may be used.3.1
32、Purified water, 18 M/cm.3.2 Concentrated nitric acid (HNO3), 65 % to 70 %, trace metal grade.3.3 Hydrogen peroxide (H2O2), 30 % ACS reagent grade.3.4 Methanol, purity 99,99 %, analytical reagent grade for matrix matching.3.5 Potassium solution, mass concentration = 10 000 mg/l in nitric acid for mat
33、rix matching.The potassium solution may be replaced by multi-element standards that contain K, if major minerals are determined simultaneously.INTERNATIONAL STANDARDISO 20649:2015(E)IDF 235:2015(E) ISO and IDF 2015 All rights reserved 1BS ISO 20649:2015ISO 20649:2015(E)3.6 Standards3.6.1 Cr/Mo/Se mu
34、lti-element stock standard solution in nitric acid, Cr= 2 mg/l, Mo= 2 mg/l and Se= 1 mg/l. High-Purity Standards1), or equivalent.3.6.2 Ge/Te multi-element stock standard solution in nitric acid, Ge= 5 mg/l and Te= 5 mg/l. High-Purity Standards1), or equivalent.3.6.3 Standard reference material SRM
35、1849a, from the National Institute of Standards and Technology (NIST) or other suitable standard reference material to serve as a control for this analysis.3.7 Preparation of standard solutionsPrepare intermediate standards from commercial stock standards at 40 ng/ml for Cr and Mo and at 20 ng/ml fo
36、r Se. Custom blended multi-element stock standard in HNO3is acceptable. Prepare three multi-element working standards containing 0,8 ng/ml, 4,0 ng/ml and 20 ng/ml Cr and Mo and 0,4 ng/ml, 2,0 ng/ml and 10 ng/ml Se, plus a blank, with both 50 ng/ml Ge and Te internal standards, in HNO3. Ge is used as
37、 the internal standard for both Cr and Mo, and Te shall be used for Se.4 ApparatusUsual laboratory glassware and equipment and, in particular, the following.4.1 Microwave oven. Use a commercial microwave designed for laboratory use at 0 C to 300 C, with a closed vessel system and a controlled temper
38、ature ramping capability. Select the vessel design that will withstand the maximum possible pressure, since organic material, and also carbonates if not given sufficient time to predigest, will generate significant pressure during digestion. Vent according to the manufacturers recommendation.CAUTION
39、 Microwave operation involves hot pressurized acid solution. Use appropriate face protection and laboratory clothing.4.2 ICP-MS. ICP mass spectrometer with collision reaction cells and hydrogen and helium source. In the collaborative study, five different mode ICP-MS instruments from three major ven
40、dors delivered equivalent performance.4.3 Various plasticware and pipets. Disposable plastic tubes/autosampler tubes to hold sample solutions, Class A volumetric pipets for standard preparation, adjustable 1 000 L micropipette or fixed 500 l pipet to add internal standards, calibrated at point of us
41、e.4.4 Analytical balance. The balance shall read to 0,0001 g.5 Procedure5.1 Sample preparationPrepare powder samples by reconstituting approximately 25 g of sample in 200 ml warm purified water (60 C). Accurately weigh approximately 1,8 g reconstituted test portion into the digestion vessel. This re
42、presents approximately 0,2 g original powder sample. SRM 1849a is weighed at 0,2 g directly into a microwave vessel. Fluid samples may be prepared by accurately weighing approximately 1 g test portion directly into the digestion vessel after mixing. For the recommended one step digestion 1) This is
43、an example of a suitable product available commercially. This information is given for the convenience of users of this document and does not constitute an endorsement by either ISO or IDF of the product named. Equivalent products may be used if they can be shown to lead to the same results.IDF 235:
44、2015(E)2 ISO and IDF 2015 All rights reservedBS ISO 20649:2015ISO 20649:2015(E)(two stages in microwave programme), add 0,5 ml of 5 000 ng/ml Ge and Te internal standard solution with a micropipette calibrated at point-of-use to deliver with at least 0,8 % accuracy. To take maximum advantage of the
45、internal standard, and thereby improve the robustness of this method, do not add the internal standards online. Add 5 ml trace metal-grade HNO3followed by 2 ml H2O2to the microwave digestion vessels. Seal the vessels according to manufacturers directions and place in the microwave. Ramp temperature
46、from ambient to 180 C in 20 min, and hold for 20 min in stage 1. In stage 2, the microwave will automatically ramp to 200 C in 20 min, and hold for 20 min, see Table 1.Table 1 Microwave operating parametersStage 1 Sample digestion1 Power 100 % (1 600 W)2 Ramp to temperature 20 min3 Hold time 20 min4
47、 Temperature 180 C5 Cool down 20 minStage 2 Sample digestion1 Power 100 % (1 600 W)2 Ramp to temperature 20 min3 Hold time 20 min4 Temperature 200 C5 Cool down 20 minFor microwave ovens without the 2-stage programme and where it is more convenient, use the 2-step digestion. Add 0,5 ml of 5 000 ng/ml
48、 Ge and Te internal standard solution (with calibrated micropipet as above) and 5 ml trace metal-grade HNO3. Do not add the internal standards online. With power settings appropriate to microwave model and number of vessels, ramp temperature from ambient to 200 C in 20 min. Hold at 200 C for 20 min.
49、 Cool vessels according to manufacturers directions, approximately 20 min. Slowly open the microwave vessels, venting the brownish nitrogen dioxide gases.CAUTION Venting shall be performed in a hood because NO2is very toxic.Add 1 ml of H2O2and redigest samples by ramping the temperature from ambient to 180 C in 15 min. Hold at 180 C for 15 min and cool for 20 min.5.2 Preparation of the test solutionAdd approximately 20 ml of purified water to the contents of the vessel with the digested samples
