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ISO 9936:2016 pdf free

ISO 9936:2016 pdf free.Animal and vegetable fats and oils
Any suitable mixture of solvents that has been proven to reach a chromatographic resolution of peaks as good as the one presented in Table 2 (relative retention time of tocopherols and tocotrienols) and in Annex A (chromatograms of a mixture of vegetable oils), should be used (see Table C.3).
A good separation of y-tocopherol and β-tocotrienol can be achieved by using a mixture of 5 % volume fraction t-butyl methyl ether + 95 % volume fraction n-heptane and a diol-column.
The preparation of a suitable mobile phase, 3,85 % (volume fraction) tetrahydrofuran solution in n-heptane, is as follows. Using a 1 000 ml graduated cylinder (6.5), introduce 1 000 ml of n-heptane (5.3)ina 2 litre bottle. Add twice 20 ml of tetrahydrofuran (5.2) using a 20 ml volumetric pipette (6.6).
Homogenize the mobile phase by means of an ultrasonic bath (6.8) for 15 min.
Prepare a stock solution of each tocol by weighing 10 mg±1 mg of the standard (5.1) into a 50 ml volumetric flask (6.7) and diluting to the mark with n-heptane (5.3).
Pipette 5 ml (6.6) of this solution into an amber glass round-bottomed flask and remove all n-heptane on a rotary evaporator (6.4) under vacuum at a temperature not greater than 40 °C. Restore atmospheric pressure with nitrogen and remove the flask from the evaporator as soon as all the solvent has been removed. Pipette into the flask 10 ml (6.6) of methanol (5.5) and swirl to dissolve the residue. Measure the maximum absorbance of this solution in a wavelength range between 270 nm and 310 nm (see appropriate wavelength in Table 1) using the UV spectrometer (6.3) witha 10-mm path length cell. The measured absorbance should be between 0,2 and 0,8. Calculate the concentration (in micrograms per millilitre) by dividing the absorbance value by the appropriate factor given in Table 1.
The following preparation of working solution is given as an example: mix appropriate volumes, for example 1 ml, of the stock calibration solutions (see 9.1.1) to obtain a mixed tocol standard solution,and dilute with n-heptane to give a solution containing between 1 μg and 5 μg of each standard per millilitre.ISO 9936 pdf download.

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