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ISO 12966-3-2009 pdf free downdload
ISO 12966-3-2009 pdf free downdload.Animal and vegetable fats and oils — Gas chromatography of fatty acid methyl esters — Part 3:Preparation of methyl esters using trimethylsulfonium hydroxide (TMSH)
Corps gras d’origines animale et végétale — Chromatographie en phase gazeuse des esters méthyliques d’acides gras — Partie 3: Preparation des esters méthyliques a Paide d’hydroxyde de triméthylsulfonium (TMSH).
Usual laboratory equipment, and in particular:
5.1 Test tubes. of capacity 2 ml with ground glass stopper (autosampler vials).
5.2 Graduated pipettes, of capacities 250 p1, 500 p1, and 1 000 jil. ISO 835111 class A.
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 part of ISO 12966. A recommended sampling method is given in ISO 5555f3)
7 Preparation of the test sample
The test sample shall be liquid, dry and clear. Proceed in accordance with ISO 661. but heat the sample to just above the melting point.
Solid samples are carefully melted at a temperature of maximum 10 C above their melting point and mixed. Avoid overheating.
Samples containing water are dissolved in petroleum ether and dried for 30 mm by addition of anhydrous sodium sulfate. The drying agent is removed by filtration through a fluted filter paper and the residue carefully washed with petroleum ether. The solvent is subsequently removed with the aid of a rotary evaporator.
8.1 Weigh, into a test tube (5.1), (10 ± 2) mg of the test sample.
8.2 Pipette (5.2) 500 p1 of TBME (4.1) into the test tube and dissolve the sample, warming gently if necessary.
NOTE For the determination of short-chain fatty acids (C4 to Ca), valeric acid methyl ester is used as an internal standard. The internal standard solution is used to dissolve the sample.
8.3 Pipette (5.2) 250 p1 of TMSH solution (4.2) into the test tube and shake vigorously for about 30 s. After this, the solution is ready for injection into the gas chromatograph. As the methyl esters are formed during injection, an injector temperature of at least 250 °C is required.
If necessary. use a mixture of TBME and methanol (9 volumes + 1 volume) to dilute the solution.
IMPORTANT — Free fatty acids react with TMSH to form the corresponding salts, which are pyrolysed to methyl esters and dimethylsulfide in the injector. Therefore, an Injector temperature of 250 C is necessary. To prevent blocking, the capillary of the split vent shall have an appropriate Internal diameter (>1 mm). It should be cleaned by regular heating or flushing with solvent. Moreover, the split vent valve shall be protected with an activated charcoal trap.
9 Test report
The test report shall contain at least the following information:
a) result of the determination:
b) the method used, together with reference to this part of ISO 12966:
c) all information necessary for the complete identification of the sample:
d) all operating details riot specified In this part of ISO 12966, or regarded as optional, together with details of any incident that may have influenced the result(s).ISO 12966-3-2009 pdf free downdload.
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