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1、 Reference number ISO 10540-2:2003(E) ISO 2003 INTERNATIONAL STANDARD ISO 10540-2 First edition 2003-02-01 Animal and vegetable fats and oils Determination of phosphorus content Part 2: Method using graphite furnace atomic absorption spectrometry Corps gras dorigines animale et vgtale Dtermination d
2、e la teneur en phosphore Partie 2: Mthode par spectromtrie dabsorption atomique avec four en graphite Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 07:52:05 MDTNo reproduction
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8、ight International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 07:52:05 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 10540-2:2003(E) ISO 2003 All rights reserved iii
9、 Foreword ISO (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 subject for which a
10、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 (IEC) on all matter
11、s of electrotechnical 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 circulat
12、ed to the member 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
13、 for identifying any or all such patent rights. ISO 10540-2 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 11, Animal and vegetable fats and oils. ISO 10540 consists of the following parts, under the general title Animal and vegetable fats and oils Determination of pho
14、sphorus content: Part 1: Colorimetric method Part 2: Method using graphite furnace atomic absorption spectrometry Part 3: Method using inductively coupled plasma (ICP) optical emission spectroscopy Copyright International Organization for Standardization Provided by IHS under license with ISO Licens
15、ee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 07:52:05 MDTNo reproduction or networking permitted without license from IHS -,-,- Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not fo
16、r Resale, 04/22/2007 07:52:05 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD ISO 10540-2:2003(E) ISO 2003 All rights reserved 1 Animal and vegetable fats and oils Determination of phosphorus content Part 2: Method using graphite furnace atomic absorp
17、tion spectrometry 1 Scope This International Standard specifies a rapid method for the determination of trace amounts of phosphorus (u 40 mg/kg) in crude or refined animal and vegetable fats and oils (hereafter referred to as fats). The limit of determination of the method is 1,0 mg/kg. 2 Normative
18、references The following referenced documents 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 661, Animal and vegetable fats and
19、 oils Preparation of test sample ISO 10540-1, Animal and vegetable fats and oils Determination of phosphorus content Part 1: Colorimetric method 3 Principle A test portion is mixed with a matrix modifier then vaporized in a graphite furnace atomic absorption spectrometer, previously calibrated using
20、 standard dilutions of soya lecithin. The phosphorus content is calculated from the absorption at a wavelength of 213,5 nm. 4 Reagents Use only reagents of recognized analytical grade, unless otherwise specified. 4.1 Cyclohexane. 4.2 Matrix modifier. Dissolve 1 g of lanthanum organometallic standard
21、 with a lanthanum content of 5 000 mg/kg in 10 ml of cyclohexane (4.1). It is essential that the lanthanum be added for the determination of the total phosphorus content. If it is omitted, the amount of phosphorus determined will vary, depending on the type of phosphatides present in the sample. Cop
22、yright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 07:52:05 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 10540-2:2003(E) 2 ISO 2003 All rights reserved
23、 NOTE A suitable lanthanum organometallic standard is available, for example, from Continental Oil Company, Ponca City, Oklahoma, USA (Conostan, 5 000 mg/kg) or from Merck, D-1600 Darmstadt, Germany (metal in standard oil, 1 000 mg/kg)1). 4.3 Blank oil: refined liquid edible oil with a phosphorus co
24、ntent below 1 mg/kg. The phosphorus content of the blank oil may be determined in accordance with ISO 10540-1. 4.4 Soya lecithin (commercial product), well-defined, with a phosphorus content of about 2 % (by mass). 4.5 Standard stock solution, with a phosphorus content of about 400 mg/kg. Dissolve 1
25、 g of soya lecithin (4.4) in 4 g cyclohexane (4.1) and add 45 g of the blank oil (4.3). Determine the phosphorus content in accordance with ISO 10540-1. 4.6 Standard working solutions, with a phosphorus content of 10 mg/kg, 20 mg/kg and 40 mg/kg respectively. Dilute the stock solution (4.5) as appro
26、priate with the blank oil (4.3). NOTE A solution with a phosphorus content of 1 mg/kg may be useful when analysing palm oil or palm fractions. 4.7 Argon, of purity 99,98 %. If argon is not available, nitrogen may be used as purge gas but it gives lower sensitivity. WARNING At temperatures above 2 30
27、0 C nitrogen forms toxic hydrogen cyanide gas, therefore continuous ventilation shall be provided in the furnace area. 5 Apparatus Usual laboratory apparatus and, in particular, the following. 5.1 Atomic absorption spectrometer, equipped with either “peak height” mode and printer or “continuous” mod
28、e and pen recorder (full-scale response in 0,2 s), together with appropriate electrode-less discharge lamp (or hollow cathode lamp) and deuterium background corrector. NOTE A Leeman atomic absorption spectrometer may be used.1) 5.2 Graphite furnace atomizer, placed in the atomic absorption spectrome
29、ter (5.1), equipped with a control unit for temperature programming. 5.3 Graphite tube, uncoated, with or without a pyrolytical platform. In combination with a platform, a pyrolytically coated graphite tube may be used as well. 5.4 Micropipettor, of capacity 20 l. 5.5 Pipettor tips. 5.6 Test tubes,
30、of capacity 10 ml. 5.7 Oven, capable of being maintained at 60 C 2 C. 5.8 Autosampler for graphite furnace atomizer (optional), with polyethylene sample cups. 1) These are examples of suitable products available commercially. This information is given for the convenience of users of this part of ISO
31、 10540 and does not constitute an endorsement by ISO of these products. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 07:52:05 MDTNo reproduction or networking permitted withou
32、t license from IHS -,-,- ISO 10540-2:2003(E) ISO 2003 All rights reserved 3 6 Sampling It is important that the laboratory receive a sample which is truly representative and has not been damaged or changed during transport or storage. Sampling is not a part of the method specified in this part of IS
33、O 10540. A recommended sampling method is given in ISO 5555. Store samples in glass or poly(ethylene terephthalate) (PET) bottles. 7 Preparation of test sample Prepare the test sample in accordance with ISO 661, ensuring that any sediment, which may be rich in phosphorus, is incorporated. 8 Procedur
34、e 8.1 Preparation of apparatus 8.1.1 Switch on the atomic absorption spectrometer (5.1) and the deuterium background corrector. 8.1.2 In accordance with the manufacturers instructions, adjust the lamp current, the slit, the wavelength and the amplification. The required wavelength for phosphorus is
35、213,5 nm. 8.1.3 Optimize the position of the graphite furnace atomizer (5.2) in the atomic absorption spectrometer (5.1) and set the required programme on the control unit of the furnace. See Table 1. Table 1 Programme for the graphite furnace programmer Temperature Ramp time Hold time Gas flow Step
36、 C s s ml/min 1 600 40 20 300 2 1 600 50 40 300 3 2 800 0 5 0 4 2 800 1 3 50 If this programme cannot be realized, use a comparable programme suitable for the particular apparatus. Place the platform, if used, in the graphite tube (5.3). Both atomization off the wall and atomization off the platform
37、 may be used. 8.1.4 Before each injection of a sample solution, pretreat the pipettor tip (5.5) by pipetting and then discarding 20 l of cyclohexane. The film of cyclohexane remaining on the wall of the tip facilitates a reproducible transfer of the sample solution. Inject 20 l of the standard worki
38、ng solution with phosphorus content of 40 mg/kg (4.6) into the graphite furnace using the micropipettor (5.4). Initiate the programme and record the absorption. Repeat these instructions until constant absorption has been reached. Each time a graphite tube is replaced, carry out three determinations
39、 with the same standard working solution (4.6) to achieve equilibrium. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 07:52:05 MDTNo reproduction or networking permitted without
40、 license from IHS -,-,- ISO 10540-2:2003(E) 4 ISO 2003 All rights reserved 8.2 Preconditioning of test sample, blank oil and working solutions At least 15 min before the determination, place the test sample (Clause 7), the blank oil (4.3) and the standard working solutions (4.6) in the oven (5.7). S
41、hake each container vigorously immediately before further analysis. If the phosphorus content is greater than 40 mg/kg, dilute the sample with blank oil (4.3). In that case, multiply the observed absorption with the dilution factor. 8.3 Determination 8.3.1 Graphite tube blank Record the absorption,
42、if any, of the graphite tube as such and auto-zero this absorption. 8.3.2 Blank oil Weight, to the nearest 0,01 g, 1,00 g of the preconditioned blank oil (4.3) in a test tube (5.6). Add 1,00 g of matrix modifier (4.2) and mix thoroughly. Inject 20 l of this mixture into the graphite furnace using th
43、e micropipettor (5.4). Initiate the programme and record the absorption. 8.3.3 Calibration of the apparatus Weigh, to the nearest 0,01 g 1,00 g of each of the three preconditioned standard working solutions (4.6) in three test tubes (5.6). To each test tube, add 1,00 g of matrix modifier (4.2) and m
44、ix thoroughly. Inject 20 l of the mixture into the graphite furnace using the micropipettor (5.4). Initiate the programme and record the absorption. Repeat until the absorption is constant. 8.3.4 Test sample Weigh, to the nearest 0,01 g, 1,00 g of the preconditioned test sample in a test tube (5.6).
45、 Add 1,00 g of matrix modifier (4.2) and mix thoroughly. Inject 20 l of the mixture into the graphite furnace using the micropipettor (5.4), initiate the programme and record the absorption. 9 Expression of results Measure the peak height on the recorder-chart or take the reading of the display or p
46、rinter. Draw a calibration curve by plotting the absorption of the three standard working solutions (8.3.3), corrected for the blank (8.3.2), against their phosphorus contents. Read the phosphorus content of the sample from the calibration curve. Express the result in milligrams per kilogram. NOTE W
47、ith the use of sophisticated equipment, autocalibration can be applied. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/22/2007 07:52:05 MDTNo reproduction or networking permitted withou
48、t license from IHS -,-,- ISO 10540-2:2003(E) ISO 2003 All rights reserved 5 10 Precision 10.1 Interlaboratory test Details of interlaboratory tests on the precision of the method are summarized in Annex A. The values derived from these interlaboratory tests may not be applicable to concentration ranges and matrices other than those given. 10.2 Repeatability The absolute difference between two independent single test results, obtained using the same met