Changes in Fatty Acid Composition during Preparative Thin-layer Chromatography.

n Thin-layer chromatography (TLC) is being used increasingly for the separation of the lipid classes (1, 2) prior to the analysis of their fatty acids by gas-liquid chromatography (GLC). Malins and Mangold (3) have described the separation of the methyl esters of fatty acids of menhaden oil from other lipid constituents and stated “the gas chromatogram of the total methyl ester fraction agreed in all details with a chromatogram obtained from a large scale preparation of these methyl esters.” This suggests that little if any autoxidation occurs during TLC. Identification of the spots is, of course, crucial to the eluting of the separate lipids. The use of iodine vapor is a favorite method (2, 3). It occurred to us that iodine may react chemically with unsaturated lipids, thus invalidating GLC studies of the eluted spots. The present study establishes this fact by showing a partial loss of polyunsaturated fatty acids after staining of the TLC plates with iodine vapor. * This research waa supported in part by PHS Research Grant AM