Structural identification of fatty acid methyl esters by collision spectra of their [M ? H]− species

Negative ion chemical ionization linked to collisionally activated decomposition (CAD) experiments has proved to be an efficient analytical tool in mass spectrometric characterization of fatty acids. The CAD mass-analysed ion kinetic energy spectra of [M ? H]^? species, obtained by OH^? reaction with a selection of six C₁₈ fatty acid methyl esters, reveal useful correlations with the original structure of the neutrals, giving evidence of both chain branching and double bond positions.