1、BRITISH STANDARD BS ISO 8070:2007 Milk and milk products Determination of calcium, sodium, potassium and magnesium contents Atomic absorption spectrometric method ICS 67.100.10 BS ISO 8070:2007 This British Standard was published under the authority of the Standards Policy and Strategy Committee on
2、28 September 2007 BSI 2007 ISBN 978 0 580 56933 3 National foreword This British Standard is the UK implementation of ISO 8070:2007. It supersedes BS 1743-20:1988 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee AW/5, Chemical analysis of milk and milk
3、 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 contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer i
4、mmunity from legal obligations. Amendments issued since publication Amd. No. Date Comments Reference numbers ISO 8070:2007(E) IDF 119:2007(E)INTERNATIONAL STANDARD ISO 8070 IDF 119 Second edition 2007-08-15 Milk and milk products Determination of calcium, sodium, potassium and magnesium contents Ato
5、mic absorption spectrometric method Lait et produits laitiers Dtermination des teneurs en calcium, sodium, potassium et magnsium Mthode spectromtrique par absorption atomique BS ISO 8070:2007ii iii Contents Page Foreword iv Foreword. v 1 Scope . 1 2 Normative references . 1 3 Terms and definitions.
6、1 4 Principle. 1 5 Reagents 2 6 Apparatus 2 7 Sampling 3 8 Preparation of test sample. 4 8.1 Milk and whey 4 8.2 Buttermilk 4 8.3 Yogurt 4 8.4 Cream. 4 8.5 Dried milk. 4 8.6 Butter 4 8.7 Cheese . 5 8.8 Caseins and caseinates . 5 9 Procedure 5 9.1 Test portion . 5 9.2 Decomposition of organic matter
7、. 6 9.3 Determination 7 10 Calculation and expression of results 8 10.1 Calculation. 8 10.2 Expression of test results 9 11 Precision 9 11.1 Repeatability 9 11.2 Reproducibility 9 12 Test report . 10 Annex A (informative) Interlaboratory trials 11 Bibliography . 14 BS ISO 8070:2007iv Foreword ISO (t
8、he 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 commit
9、tee 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 electrotech
10、nical 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
11、 bodies for voting. Publication as an International 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
12、 any or all such patent rights. ISO 8070 IDF 119 was prepared by Technical Committee ISO/TC 34, 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 8070 IDF 119 cancels and re
13、places the first edition (ISO 8070:1987), which has been technically revised. BS ISO 8070:2007 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 Committee has the right to be represented
14、 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. Draft International Standards adopted by the Action Teams and Standing Committees are circulated to the National Comm
15、ittees for voting. Publication as an International Standard requires approval by at least 50 % of the IDF National 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 id
16、entifying any or all such patent rights. ISO 8070 IDF 119 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 ISO. All work was carried out by the Joint ISO-IDF
17、Action Team Minor compounds, of the Standing Committee on Minor components and characterization of physical properties, under the aegis of its project leaders, Mr L. Nol (FR) and Mr. M. Carl (DE). This edition of ISO 8070 IDF 119 cancels and replaces IDF 119A:1987 and IDF 154:1992, which have been t
18、echnically revised. BS ISO 8070:2007 blank 1 Milk and milk products Determination of calcium, sodium, potassium and magnesium contents Atomic absorption spectrometric method 1 Scope This International Standard specifies a flame atomic absorption spectrometric method for the determination of calcium,
19、 sodium, potassium and magnesium contents in milk and milk products. The method is applicable for milk and whey, buttermilk, yogurt, cream, dried milk, butter, cheese, casein and caseinate. 2 Normative references The following referenced documents are indispensable for the application of this docume
20、nt. For dated references, only the edition cited applies. 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
21、 laboratory use Specification and test methods 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 calcium, sodium, potassium, magnesium contents mass fraction of substances determined by the procedure specified in this International Standard NOT
22、E The respective contents are expressed in milligrams per gram. 4 Principle The organic matter is decomposed by dry ashing or by wet digestion using nitric acid either in an open microwave-assisted wet digestion system or in a pressurized microwave-assisted wet digestion system or in a pressurized p
23、olytetrafluoroethylene (PTFE) decomposition vessel or any appropriate instrumentation in wet digestion. The ash containing calcium, sodium, potassium, and magnesium is dissolved in a nitric acid solution in the case of dry ashing, or the digests diluted in the case of wet digestion. The test and cal
24、ibration solutions are atomized into an airacetylene flame of an atomic absorption spectrometer and their absorption is measured at appropriate wavelengths. BS ISO 8070:20072 5 Reagents Use reagents of recognized analytical grade, unless otherwise specified, and water complying with grade 2 in accor
25、dance with ISO 3696, unless otherwise stated. SAFETY PRECAUTIONS When using acids, operators should protect themselves by wearing glasses and gloves. Manipulation of acids shall be done under an appropriate fume hood. 5.1 Nitric acid (HNO 3 ), concentrated, with a mass fraction of 65 %. 5.2 Nitric a
26、cid (HNO 3 ) solution, with a volume fraction of 25 %. Dilute 25 ml of nitric acid (5.1) to 100 ml with water and mix. 5.3 Lanthanum trichloride solution, with c(LaCl 3 .7H 2 O) = 27 g/l. Dissolve 27 g of lanthanum trichloride heptahydrate (LaCl 3 .7H 2 O) in an amount of water. Dilute to 1 litre an
27、d mix. 5.4 Calcium ion stock solution. Commercially available or equivalent corresponding to c(Ca 2+ ) = 1 g/l. 5.5 Sodium ion stock solution. Commercially available or equivalent corresponding to c(Na + ) = 1 g/l. 5.6 Potassium ion stock solution. Commercially available or equivalent corresponding
28、to c(K + ) = 1 g/l. 5.7 Magnesium ion stock solution. Commercially available or equivalent corresponding to c(Mg 2+ ) = 1 g/l. 5.8 Standard working solution, containing 100 mg/l calcium, 20 mg/l sodium, 20 mg/l potassium and 10 mg/l magnesium ions. Pipette 10 ml of calcium ion stock solution (5.4),
29、2 ml sodium ion stock solution (5.5), 2 ml potassium ion stock solution (5.6) and 1 ml magnesium ion stock solution (5.7) into a 100 ml one-mark volumetric flask (6.3) and mix. Add 5 ml of nitric acid solution (5.2). Dilute to the 100 ml mark with water and mix again. Store the standard working solu
30、tion in a PE-HD bottle (6.7) so that any contamination is avoided. 5.9 Light petroleum (petroleum ether), with a boiling range of between 40 C and 60 C. Distil the light petroleum, if necessary, in a contamination free distillation unit. 5.10 Hydrogen peroxide (H 2 O 2 ), with a volume fraction of 3
31、0 %. 6 Apparatus 6.1 General Keep the clean glassware in a nitric acid solution with a mass fraction of about 10 %. Clean all glassware and plastic ware thoroughly with the 10 % nitric acid and keep it in that solution for at least 6 h. Before use, rinse the glassware and plastic ware three times wi
32、th double-distilled water and allow it all to dry. BS ISO 8070:2007 3 Store the clean glassware and plastic ware in a dust-free environment to ensure that they are free from any contamination when used. Usual laboratory apparatus, and in particular, the following. 6.2 Analytical balance, capable of
33、weighing to the nearest 1 mg, with a readability of 0,1 mg. 6.3 One-mark volumetric flasks, of nominal capacities 20 ml, 50 ml, 100 ml, 250 ml and 1000 ml, complying with the requirements of ISO 1042. 6.4 One-mark pipettes, of nominal capacities 1 ml, 2 ml, 5 ml and 10 ml, complying with the require
34、ments of ISO 648. 6.5 Micropipette, capable of adjusting to between 1 ml and 5 ml, with plastic pipette tips. 6.6 Graduated measuring cylinder, of capacity 10 ml. 6.7 High-density polyethylene (PE-HD) bottles, capable of storing the standard and sample solutions. 6.8 Silica crucibles, of capacity be
35、tween 25 ml and 50 ml. 6.9 Programmable furnace oven, capable of attaining a minimum temperature of 550 C 25 C and of programming with a heating rate of 50 C/h. 6.10 Open focused microwave-assisted wet digestion system, delivering 200 W microwave power, equipped with appropriate vessels of capacity
36、50 ml, with an adapted cooling system. 6.11 Pressurized microwave-assisted wet digestion system, with operator selectable output of between 0 W and 1 000 W microwave power, provided with temperature and pressure controllers and an air cooling device, equipped with appropriate vessels of capacity 50
37、ml, commercially available or equivalent. 6.12 Decomposition vessels, made of stainless steel, with adapted PTFE inner vessels of capacity 23 ml with screw caps (pressurized wet decomposition PTFE vessel), commercially available or equivalent. 6.13 Oven, capable of attaining a temperature of 150 C (
38、for digestion bombs). 6.14 Flame atomic absorption spectrometer, with an airacetylene burner, suitable for measuring at different wavelengths: at 422,7 nm for calcium, at 589,6 nm for sodium, at 766,5 nm for potassium and 285,2 nm for magnesium ion content-determination procedures; equipped with hol
39、low cathode lamps of single element type or combined type. 6.15 Water baths, capable of maintaining temperatures of 20 C 2 C, at 40 C 1 C, at 45 C 1 C, and at 65 C 1C. 6.16 Centrifuge, capable of producing a radial acceleration of 2 500g, with tubes of capacity at least 150 ml. 6.17 Appropriate grin
40、ding device. 6.18 Sieve, free of contaminated material, with nominal size of aperture 0,5 mm. 7 Sampling A representative sample should have been sent to the laboratory. It should not have been damaged or changed during transport or storage. Sampling is not part of the method specified in this Inter
41、national Standard. A recommended sampling method is given in ISO 707 IDF 50. Store the test sample in such a way that deterioration and change in its composition are prevented. BS ISO 8070:20074 8 Preparation of test sample Avoid any contamination of the test sample. 8.1 Milk and whey Place the test
42、 sample in the water bath (6.15) set at 20 C and mix carefully. If in the case of milk the fat is not evenly dispersed, warm the test sample slowly in a water bath (6.15) set at 40 C. Mix gently by inversion only. When the sample is mixed thoroughly then cool quickly again in the water bath (6.15) s
43、et at 20 C. 8.2 Buttermilk Remove, if necessary, any butter granules. Immediately before weighing (9.1.1.1 or 9.1.2.1), place the test sample in the water bath (6.15) set at 20 C and mix carefully. 8.3 Yogurt Place the test sample in the water bath (6.15) set at 20 C and mix carefully. If the serum
44、separates, stir the sample vigorously immediately before weighing (9.1.1.1 or 9.1.2.1). 8.4 Cream Place the test sample in the water bath (6.15) set at 20 C. Mix or stir thoroughly but not so vigorously as to cause frothing or churning. If the cream is very thick, or if the fat is not evenly dispers
45、ed, warm the sample slowly in a water bath (6.15) set at 40 C to facilitate mixing. Cool the test sample quickly in the water bath (6.15) set at 20 C. NOTE Reliable results cannot be expected if adequate mixing of the test sample is not achieved or if the test sample shows any evidence of churning o
46、r any other signs of abnormality. 8.5 Dried milk Transfer the test sample into a container of capacity about twice the volume of the sample and provided with an airtight lid. Close the container immediately. Mix the milk powder thoroughly by repeatedly shaking and inverting the container. 8.6 Butter
47、 Because of the possible inhomogeneous distribution of the ions in butter they are determined in the serum. NOTE The ion contents in the fat fraction, obtained from butter in the way described, are negligible compared with the contents in the serum and can be ignored. Weigh, to the nearest 100 mg, 1
48、00 g of test sample in a dry centrifuge tube (6.16), of which the mass has been determined previously. Place the tube in a water bath (6.15) set at 45 C. As soon as the butter is melted, centrifuge the tube with a radial acceleration of 2 500g. Remove as much as possible the clear fat layer from the
49、 tube by using a pipette. Add 10 ml light petroleum (5.9) to dilute the remaining fat layer in the tube and remove the mixture again with a pipette. Repeat the addition and removal of light petroleum mixture twice. Remove the residual light petroleum by warming the tube in a water bath (6.15) set at 65 C. Cool in the water bath (6.15) set in advance at 20 C. Dry the outside of the tube with a clean paper tissue. Weigh the tube and
