ANALYSIS OF LOW ERUCIC-ACID TURNIP RAPESEED OIL (BRASSICA-CAMPESTRIS) BY NEGATIVE-ION CHEMICAL IONIZATION TANDEM MASS-SPECTROMETRY - A METHOD GIVING INFORMATION ON THE FATTY-ACID COMPOSITION IN POSITIONS SN-2 AND SN-1/3 OF TRIACYLGLYCEROLS

A tandem mass spectrometric method is described for the rapid analysis of fatty acid combinations in mixtures of triacylglycerols. Triacylglycerols were introduced into a triple quadrupole mass spectrometer via a direct exposure probe and deprotonated using ammonia negative ion chemical ionization. Collisionally activated spectra were obtained and the resulting fragments used to identify the fatty acid constituents, and the fatty acids preferentially located at the sn-2 position of the triacylglycerols. Fourteen major molecular weight species of purified triacylglycerols of a supercritical fluid extract of low erucic acid turnip rapeseed oil (Brassica campestris) were analyzed. The five major combinations of fatty acids comprised two thirds of the total triacylglycerols and contained oleic, linoleic and alpha-linolenic acids with linoleic acid favoring the sn-2 position.