Analytical aspects of capillary gas chromatography of lower fatty acids [up to C18]

The principal aspects influencing analytical capillary gas chromatography of fatty acids up to C18 have been evaluated. Selected fundamental problems of interlaboratory exchange of retention data were problems of defined temperature in commercial thermostated air baths, of capillary tubing, and of stationary phases. A modification of commercial thermostats has been proposed in order to secure a defined temperature for glass capillary columns. It has been found that retention data of fatty-acid methyl esters can be measured under standard conditions with the same accuracy as retention data of hydrocarbons on squalane. Metal capillary columns coated with Apiezon L were found to be unsuitable for the analysis of fatty-acid methyl esters when compared with the results of their quantitative analysis in packed Apiezon L and polar capillary columns. Possibilities of a nontraditional statistical evaluation of the results of measurements are suggested. A program in FORTRAN IV language is given for the calculation of Kovats' retention indices for fatty-acid methyl esters.