Mass spectrometric analysis of long-chain esters of diols.

Homologous series of synthetic long-chain monoesters and diesters of 1,2-ethanediol were analyzed by mass spectrometry, and the patterns of fragmentation were studied. Under electron impact saturated ethanediol monoesters yielded prominent ions characteristic of the short-chain diol, such as the rearranged ion formed by 2,3-cleavage (m/e 104) and the ion caused by 3,4-cleavage (m/e 117). Fragments characteristic of the constituent long-chain moieties were the acylium ions RCO, RCO - 1, and the ions RC(OH)(2). The mass spectra of ethanediol diesters exhibited very intense peaks due to the ions formed by loss of the acyloxy group, M - RCOO, or one carboxylic acid, M - RCOOH. These ions are distinctive for diol diesters. Precise mass measurements by high resolution mass spectrometry verified the composition of the ion fragments. Spectral studies of some monoesters and diesters of 1,3-propanediol, 1,4-butanediol, 2,3-butanediol, and also of some monounsaturated homologues, demonstrated that mass spectrometry is very suitable for the identification, distinction, and analysis of diol lipids.