O-CENTER-DOT AND OH- CHEMICAL-IONIZATION OF SOME FATTY-ACID METHYL-ESTERS AND TRIACYLGLYCEROLS

O-. and OH- react with fatty acid methyl esters (FAMES) under chemical ionization conditions both as Bronsted bases to form [M - H]- and as nucleophiles to form the carboxylate ion RCOO-. O-. shows a much great er tendency to react as a nucleophile than does OH-. The [M - H] ions fragment by elimination of CH,OH, with unsaturation in certain positio ns in the fatty acid hydrocarbon chain promoting this elimination for unknown reasons. The reaction of O-. and OH with triacylglycerols lead s to [M - H]-, characteristic of the molecular mass, and to carboxylat e ions characteristic of the fatty acid(s) present in the lipid. The p resence of the three ester functions in the lipids greatly enhances th e formation of carboxylate ions compared to the FAMES.