Detection of Certain Brominated Long-Chain Fatty Acid Esters by Gas Liquid Chromatography

Abstract

EVIDENCE has recently been presented which demonstrated the effects of alteration of the chemical composition of the stationary liquid upon the resolution of the methyl esters of long-chain saturated and unsaturated fatty acids by gas-liquid chromatography^1–4. When the adipate, glutarate and succinate polyesters of diethylene glycol were used as liquid phases, the more polar unsaturated fatty acid esters were retained on the column to a greater degree than the saturated members of similar carbon chain-length. The number and position of the unsaturated linkages appeared to be the dominating factors in determining the affinity of the component vapour for the stationary liquid. The greater the degree of unsaturation beyond the 9,10 position in the fatty acid ester molecule, the slower was the movement of the substance down the column. This effect appeared to be modified somewhat by the occurrence of a double bond closer to the carboxyl group, that is, before the 9,10 position, which tended to hasten the emergence of the compound from the column. Although the polyesters were much more efficient as stationary liquids than the comparatively non-polar ‘Apiezon’ and silicone greases^5,6 for achieving separations of saturated and unsaturated fatty acid esters, when samples of fatty acid esters of unknown composition were analysed by gas-liquid chromatography, the possible presence of esters of branched-chain acids, odd-numbered acids, and unusual mono-, di- and poly-unsaturated acids still made difficult the positive identification of the individual components on the basis of comparative retention times and volumes.