ONLINE DERIVATIZATION FOR COMPLEX FATTY-ACID MIXTURES BY CAPILLARY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

An on-line derivatization method for analysis of fatty acids involving co-injection of sample and reagent, followed by a gas phase derivatization reaction in the injection port of the gas chromatograph is described. The derivatizing reagent employed to convert fatty acids to their respective trimethylsilyl (TMS) esters was bis(trimethylsilyl)trifluoro- acetamide (BSTFA). Tetradecane was used as an internal standard. Reagent (2 μL) was co-injected with 1 μL of sample at 220°C. Saturated and unsaturated as well as branched and straight-chain fatty acids are derivatized with equal effectiveness. The on-line procedure does not add any time beyond that required for the gas chromatographic analysis. To demonstrate the identification and quantitation of fatty acids, the distribution of fatty acids in various food oils (corn, sesame, sunflower, canola, safflower, peanut, and olive) was determined. Results obtained by the on-line technique are consistent with previously published compositions for these oils. © Oxford University Press 1993.