Gas Chromatographic Retention Time Rule and Mass Spectrometric Fragmentation Rule of Fatty Acids and Its Application in Food

The fat in food samples was extracted using Soxhlet technique, and in-vial derivatized to their corresponding methyl ester and subsequently analyzed by GC/MS. Sufficient separation for the homologous and isomers of methyl esters of fatty acids was achieved with HP-88 capillary column. The gas chromatographic retention time rule of homologues and isomers of fatty acids methyl esters was studied, and mass spectrometric fragmentation rule was also investigated in this study. A novel method which can ascertain the carbon atom number and double bond number in fatty acids using 3 characteristic ions, as well as can confirm cis- and trans-isomers and double-bond positional isomers based on retention time rule, was established. Using this method, the contents of homologues and different kinds of isomers of fatty acids can be determined without standards. This method can be applied to the investigation of the compositions of fatty acids, especially trans-fatty acid, and determination fatty acids in lipid and food samples. The method is accurate, reliable, and convenient, and has been applied to the quantitative determination of the content of trans-fatty acid in food samples.