Identification of monoacyl- and monoalkylglycerols by gas--liquid chromatography--mass spectrometry using polar siloxane liquid phases

Abstract

A comparative study was made of the spectra obtained after gas-liquid chromatography-mass spectrometry of the trimethylsilyl ethers of 1- and 2-monoacyl- and monoalkyl-glycerols. The glycerol derivatives were resolved on the basis of positional substitution and the degree of unsaturation on Silar-5CP (a cyanopropylphenylsiloxane) liquid phase, and the peaks were examined in a Varian MAT CH-5 single-focusing mass spectrometer. The 1-monoacyl- and 1-monoalkylglycerols possessed m/e M - 103 and m/e 205, respectively, as unique peaks, while the 2-monoacyl- and 2-monoalkylglycerols contained m/e 218 as the highly favored fragment. These differences were large and consistent enough to serve as a basis for identification and quantitation of the isomers in a mixture. The saturated and unsaturated monoacyl- and monoalkylglycerols differed markedly in the kind and intensity of the base peaks and other major fragments. In view of the effective gas-liquid chromatographic resolution of these compounds, the marked differences in the spectra of the trimethylsilyl ethers of the saturated and unsaturated species provided a distinct advantage for their identification by the gas-liquid chromatography-mass spectrometry system.