Separation of cis/trans fatty acid isomers on gas chromatography compared to the Ag-TLC method

Abstract

Separation of cis/trans fatty acids isomers on gas chromatography compared to the Ag-TLC method The present study investigates the separation of the cis/trans isomers of fatty acids on the 75 m SP2560 column under different gas chromatographic (GC) conditions including an isothermal program and a time-temperature program. The time-temperature program showed improved separation of cis/trans isomers of C-14:1, C-16:1, C-18:1, C-18:2 and C-18:3 fatty acids along with short chain fatty acids compared to the isothermal program. The separation of trans/trans isomers of C-18.1 fatty acids including elaidic acid (C-18:1 Delta 9t) and vaccenic acid (C-18:1 Delta 11t) was difficult with the time-temperature program. The thin layer chromatography impregnated with silver nitrate (Ag-TLC) method was performed to separate cis/trans fractions and GC analysis was carried out with the trans fraction. But GC analysis showed a co-elution of trans isomers of C-18:1 fatty acid. Thus the study shows that a time-temperature programmed GC method with the highly polar cyanopropyl column is sufficient to resolve trans fatty acids along with short chain fatty acids when a large number of samples has to be analyzed.