1、 Reference numbers ISO/TS 6733:2006(E) IDF/RM 133:2006(E) ISO and IDF 2006TECHNICAL SPECIFICATION ISO/TS 6733 IDF/RM 133 First edition 2006-11-01 Milk and milk products Determination of lead content Graphite furnace atomic absorption spectrometric method Lait et produits laitiers Dtermination de la
2、teneur en plomb Mthode spectromtrique dabsorption atomique avec four de graphite ISO/TS 6733:2006(E) IDF/RM 133:2006(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typef
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7、 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 Web www.iso.org Web www.fil-idf.org Published in Switzerland ii ISO and IDF 2006 All rights reservedISO/TS 6733:2006(E) IDF/RM 133:2006(E) ISO and I
8、DF 2006 All rights reserved iii Contents Page Foreword iv Foreword. v Introduction . vi 1 Scope . 1 2 Normative references . 1 3 Terms and definitions. 1 4 Principle. 1 5 Reagents 2 6 Apparatus 3 7 Sampling 3 8 Preparation of test sample. 4 9 Procedure 4 9.1 Dry ashing . 4 9.2 Mineralization in a cl
9、osed vessel (bomb digestion) 5 9.3 Measurements. 5 10 Calculation and expression of results 7 10.1 Automated calculation . 7 10.2 Calculation using a calibration graph. 7 10.3 Calculation using standard additions. 8 10.4 Expression of results . 8 11 Precision 9 11.1 Interlaboratory test . 9 11.2 Rep
10、eatability 9 11.3 Reproducibility 9 12 Test report . 9 Annex A (informative) Interlaboratory trials 10 Annex B (informative) Applicability of dry ashing as a mineralization procedure 12 Bibliography . 13 ISO/TS 6733:2006(E) IDF/RM 133:2006(E) iv ISO and IDF 2006 All rights reservedForeword ISO (the
11、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 subject for which a technical committee
12、 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 (IEC) on all matters of electrotechnic
13、al standardization. International Standards 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 bo
14、dies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. In other circumstances, particularly when there is an urgent market requirement for such documents, a technical committee may decide to publish other types of normative d
15、ocument: an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in an ISO working group and is accepted for publication if it is approved by more than 50 % of the members of the parent committee casting a vote; an ISO Technical Specification (ISO/TS) repr
16、esents an agreement between the members of a technical committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting a vote. An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a further three years, revi
17、sed to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is confirmed, it is reviewed again after a further three years, at which time it must either be transformed into an International Standard or be withdrawn. Attention is drawn to the possibility that some of the elements
18、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/TS 6733 IDF/RM 133 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products, and the International Dairy Federatio
19、n (IDF). It is being published jointly by ISO and IDF. ISO/TS 6733:2006(E) IDF/RM 133:2006(E) ISO and IDF 2006 All rights reserved v Foreword IDF (the International Dairy Federation) is a worldwide federation of the dairy sector with a National Committee in every member country. Every National Commi
20、ttee has 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. The main task of technical committees is to prepare International Standards. Draf
21、t 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 National Committees casting a vote. In other circumstances, particularly when the
22、re is an urgent market requirement for such documents, a Standing Committee may decide to publish an other type of normative document which is called by IDF: Reviewed method. Such a method represents an agreement between the members of a Standing Committee and is accepted for publication if it is ap
23、proved by at least 50 % of the committee members casting a vote. A Reviewed method is equal to an ISO/PAS or ISO/TS and will, therefore, also be published jointly under ISO conditions. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent right
24、s. IDF shall not be held responsible for identifying any or all such patent rights. ISO/TS 6733 IDF/RM 133 was prepared by the International Dairy Federation (IDF) and Technical Committee ISO/TC 34, Food products, Subcommittee SC 5, Milk and milk products. It is being published jointly by IDF and IS
25、O. All work was carried out by the Joint ISO-IDF 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/TS 6733 IDF/RM 133 cancels and replaces IDF 133A:1
26、992, which has been technically revised. ISO/TS 6733:2006(E) IDF/RM 133:2006(E) vi ISO and IDF 2006 All rights reservedIntroduction The method described in the first edition of IDF 133A:1992 was not up-to-date, was based on another technique and also did not fulfil the requirements for a fully valid
27、ated International Standard. A new interlaboratory test on the up-dated method as described in this Technical Specification (Reviewed Method) was organized in 2004 in accordance with ISO 5725-1 and ISO 5725-2. However, the requirements for a reliable study were not fulfilled due to outliers, lack of
28、 participants and misinterpretations on the use of the method. To maintain the method because several laboratories are using it, experts decided to publish the method as an ISO Technical Specification and IDF Reviewed Method rather than an International Standard. TECHNICAL SPECIFICATION ISO/TS 6733:
29、2006(E) IDF/RM 133:2006(E) ISO and IDF 2006 All rights reserved 1 Milk and milk products Determination of lead content Graphite furnace atomic absorption spectrometric method 1 Scope This Technical Specification describes a method for the quantitative determination of the total lead content in milk
30、and milk products. The detection limit of the method, defined as three times the standard deviation of the blank determination, is 0,001 mg/kg for liquid products and 0,01 mg/kg for solid products if dry ashing is applied. For pressurized wet mineralization, these figures are the same for test porti
31、ons containing 0,2 g of dry matter. Microwave mineralization allows for larger test portions, and detection limits are accordingly lower. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited app
32、lies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 648, Laboratory glassware One-mark pipettes ISO 1042, Laboratory glassware One-mark volumetric flasks ISO 3696, Water for analytical laboratory use Specification and test methods ISO 6
33、732:1985, Milk and milk products Determination of the iron content Spectrometric method (Reference method) 1)3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 lead content mass fraction of substance determined by the procedure specified in this
34、 Technical Specification NOTE The lead content is expressed as milligrams per kilogram of sample. 4 Principle A test portion is mineralized by means of programmed dry ashing with sulfuric acid as the ashing aid. Alternatively, it is mineralized by pressurized wet mineralization with nitric acid in a
35、 teflon or quartz vessel, or by microwave wet mineralization. The ash is dissolved in dilute nitric acid, or the wet mineralisate is evaporated to dryness and the residue is dissolved in dilute nitric acid. The atomic absorption of the resulting 1) Equivalent to IDF 103A. ISO/TS 6733:2006(E) IDF/RM
36、133:2006(E) 2 ISO and IDF 2006 All rights reservedsolution is measured at a wavelength of 283,3 nm with a graphite furnace atomic absorption spectrometer with Zeeman or deuterium-arc background correction. Quantification is carried out by means of a calibration graph or by the method of standard add
37、itions. 5 Reagents Unless otherwise stated, all reagents and solvents shall be of analytical reagent (AR) grade. 5.1 Water, double-distilled or of similar purity, complying with the requirements of ISO 3696, grade 2. 5.2 Concentrated nitric acid (HNO 3 ), 20 (HNO 3 ) = 1,40 g/ml, for cleaning purpos
38、es. 5.3 Concentrated nitric acid (HNO 3 ), 20 (HNO 3 ) = 1,40 g/ml, Merck “Suprapur“2)or equivalent. 5.4 Concentrated sulfuric acid (H 2 SO 4 ), 20 (H 2 SO 4 ) = 1,84 g/ml, Merck “Suprapur“2)or equivalent. 5.5 Sulfuric acid solution, 20 % (mass/volume fraction). Dilute 130 ml of concentrated sulfuri
39、c acid (5.4) with water to 1 000 ml. 5.6 Matrix modifiers. 5.6.1 Dissolve 2,0 g of ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ) (Baker “Ultrex“)2)and 0,17 g of magnesium nitrate Mg(NO 3 ) 2 6H 2 O (Merck “Suprapur“) in water. Dilute to 100 ml. Suitable solutions are also commercially available e.g
40、. from Perkin-Elmer No. B019-06342)(1 % Mg solution) and No. N930-3445 (10 % NH 4 H 2 PO 4solution). 5.6.2 Mix 200 l of a solution containing 1 % Pd (as nitrate, e.g. Perkin-Elmer No. B019-0635)2)and 20 l of a solution containing 1% Mg (as nitrate, e.g. Perkin-Elmer No. B019-0634)2)with 1,67 ml of w
41、ater and 2 drops of nitric acid (5.3) 5.7 Concentrated lead standard solution, c(Pb) = 100 mg/l. Dissolve 159,9 mg of lead nitrate Pb(NO 3 ) 2 in water in a 1 000 ml one-mark volumetric flask (6.4). Add 10 ml of concentrated nitric acid (5.3). Dilute to the mark with water and mix. Store the solutio
42、n in a borosilicate glass bottle with a ground glass stopper. NOTE As an alternative, a commercially available standard solution may be used, e.g. Merck Titrisol 99692) . 5.8 Standard lead solution, c(Pb) = 1 mg/l. Pipette 1,0 ml of concentrated lead standard solution (5.7) into a 100 ml volumetric
43、flask (6.4). Add 1 ml of concentrated nitric acid (5.3). Dilute to the mark with water and mix. Store the solution in a polyethylene flask (6.6) with a screw cap. 5.9 Working lead standard solutions. Pipette 0 ml, 0,50 ml, 1,0 ml, 2,0 ml, and 3,0 ml, respectively, of standard lead solution (5.8) int
44、o 100 ml one- mark volumetric flasks (6.4). Add 1 ml of nitric acid (5.3). Dilute to the mark with water and mix. Prepare the working lead standard solutions every week. 2) Baker “Ultrex”, Merck “Suprapur”, Titrisol and Perkin-Elmer solutions are examples of products available commercially. This inf
45、ormation is given for the convenience of the users of this Technical Specification and does not constitute an endorsement by ISO or IDF of these products. ISO/TS 6733:2006(E) IDF/RM 133:2006(E) ISO and IDF 2006 All rights reserved 3 NOTE These working lead standard solutions have concentrations of 0
46、,0 g/l, 5,0 g/l, 10,0 g/l, 20,0 g/l and 30,0 g/l of lead, respectively. Store the working lead standard solutions for not more than one week in polyethylene flasks (6.6) with screw caps. 5.10 Ultrapure nitrogen or argon. 6 Apparatus Usual laboratory equipment and, in particular, the following. 6.1 C
47、rucibles and glassware, cleaned as follows. Wash and rinse with tap water, then rinse with distilled water. Soak in 10 % (mass fraction) concentrated nitric acid (5.2) for at least 12 h. Rinse three times with double-distilled water before use. Allow to dry and store the thus-cleaned crucibles and g
48、lassware in a dust-free environment. 6.2 Analytical balance, capable of weighing to the nearest 0,1 mg. 6.3 Quartz crucibles, flat bottomed, with covers (lids), of capacity approx. 25 ml to 50 ml. 6.4 One-mark volumetric flasks, of capacities 10 ml, 100 ml and 1 000 ml, with ground glass stoppers. 6
49、.5 One-mark pipettes, of capacities 1 ml, 2 ml and 10 ml. 6.6 Polyethylene flasks, of capacity 100 ml, with screw caps. 6.7 Dosing pipettes, with adjustable volumes of between 50 l and 250 l, between 250 l and 1 000 l and between 1 000 l and 5 000 l, with plastic tips. 6.8 Muffle furnace, temperature-programmable to approx. 800 C, with a lining of material with a low lead content (e.g. quartz). Heat the muffle furnace regularly (e.g. once a fortnight) to a temperature of between 700 C and
