ISO 12966-1-2014 pdf free download.Animal and vegetable fats and oils – Gas chromatography of fatty acid methyl esters – Part 1: Guidelines on modern gas chromatography of fatty acid methyl esters. 5 Columns At the time of publication of this part of ISO 12966, for the separation of FAM Es, wall coated open tubular (WCOT) capillaries are used as they offer a number of advantages over a packed column. This includes vastly improved separations with higher resolution, reduced time of analysis, smaller sample size and higher sensitivities. All this is enabled by the possibility of using very long columns with a large number of theoretical plates. Sample capacity increases with the column diameter, smaller diameters giving greater efficiency and better resolutions. Therefore for complex samples columns with small diameters and small sample capacity are used. Common available internal diameters (ID) are 0,1 mm (fast GC columns) to 0,53 mm (wide bore column), film thickness is between 0,1 pm and 0,3 tim. The column diameter shall suit the type of sample inlet system: 0,20 mm, 0,25 mm or 0,32 mm ID column are for split and splitless injection systems. 0,32 mm ID for splitless and on-column injections, and 0,53 mm ID for direct injection systems. Retention and sample capacity increase with increasing film thickness, at the same time the column efficiency decreases. Film thickness is inversely related to plate number, but directly proportional to the time of analysis. This also means that a greater film thickness gives greater retention, which requires a higher oven temperature in isothermal conditions. The length of the columns is 10 m to 100 m depending on the required resolution and separation problem. With short columns limited, but fast, information can be obtained, in process control, etc. Different types of capillary columns with non-polar, polar, and highly polar stationary phases are used for the separation of FAMEs. The elution order for columns with different polarity are shown in ISO 12966-4 (see Annex B and Annex C). Fused silica columns coated with highly polar stationary phases of cyanoalkyl polysiloxane are used for the analysis of samples with complex mixtures of geometrical and positional isomers of polyunsaturated fatty acids (PUFA). The main advantage of these high-polar phases compared to non-polar phases is their high-resolution capability of unsaturated FAME, especially for the separation of cis and trans FA isomers. However, the polarity of this column shows less thermal stability compared...
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