Selection of methylation procedures for quantitation of short-chain glycerol-bound compounds formed during thermoxidation

Five methylation procedures, including base- and acid-catalyzed methods, we re tested in thermoxidized methyl linoleate and trilinolein, in order to qu antitate major oxidation short-chain glycerol-bound compounds by gas chroma tography. Results indicated that transmethylations using KOH in methanol or CH3ONa-CH3OH in tert.-butylmethyl ether were the most appropriate methods, given the excellent reproducibility and practically complete recovery obta ined for the compounds of interest, mainly short-chain fatty acids and alde hydic acids. Also, formation of acids from aldehydes during thermoxidation as well as modifications of aldehydic functions under acidic conditions, su ch as conversion to acetals, were checked using dodecanal as model aldehyde . (C) 1999 Elsevier Science B.V. All rights reserved.