Structural Characterization of Wax Esters by Electron Ionization Mass Spectrometry

Abstract
The most important fragments indicative of the structure of the acid and alcohol chains are identified and summarized for WEs with various number of double bonds in the chains. Briefly, most WEs provide acylium ions allowing structural characterization of the acid part, whereas the alcohol part give corresponding alkyl radical cations. The elemental composition of selected important fragments is established from a high-resolution accurate mass analysis. The ion abundances are discussed with respect to the length and unsaturation of the aliphatic chains. The interpretation of the spectra of branched or unsaturated WEs requires the recognition of small but important peaks that are difficult to discern among the other fragments. We demonstrate that such fragments are easily detected in differential mass spectra. This approach requires spectra of WE standards (e.g., straight-chain analogues in case of branched WEs) recorded under the same experimental conditions. The WEs mass spectral database provided in the Supplemental Data can be used as a reference for the analysis of the GC/EI-MS data.

The article is published online in the Journal of Lipid Research and is free to access.