Abstract: Using gas chromatography-flame ionization detector (GC-FID) fitted with a CP-Sil88 capillary column as the analytical column, we investigated the effects of different carrier gases (helium and nitrogen) on the resolution and quantitative accuracy of C18:1 cis-trans fatty acid isomers in shortening, butter, biscuit and cake, as well as C18:2 and C18:3 cis-trans fatty acid isomers in vegetable oil under isothermal or rising temperature conditions. With helium as carrier gas, the resolution (R) of C18:1 13t,14t(6-8c) and C18:1 9c was greater than 1.0, which could clearly distinguish and separate 4t–13t,14t isomers at different concentrations, and accurate quantification was achieved without underestimating the total amount of C18:1 trans fatty acid isomers. The carrier gas had no effects on the resolution or content of C18:2 cis-trans isomers in vegetable oil. Compared with nitrogen, helium had a slight advantage in the separation of C18:3 trans isomer in vegetable oil, while no significant difference was noted between the values obtained using them as carrier gases. Compared with nitrogen, helium was more suitable for use as carrier gas for simultaneous determination of trans fatty acids, saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids in foods with higher quantitative accuracy and wider versatility.

Key words: cis-trans fatty acid isomers; resolution; operating temperature; carrier gas; CP-Sil88 capillary column