Content area
Full text
Abstract
Dimethyl disulfide (DMDS) adducts are prepared from fatty acid methyl esters to locate the double-bond position in monoenoic fatty acids by gas chromatography/mass spectrometry. We improved our original procedure for preparing DMDS adducts with a simple device that can be made in any laboratory using a glass pipette and silica based packing material, Extelut NT.
Keywords Dimethyl disulfide adduct preparation * Double-bond position * Monoenoic fatty acid
Sir
In 1981, Francis [1] reported the usefulness of dimethyl disulfide (DMDS) adducts for locating the double-bond position in an authentic monoenoic fatty acid methyl ester by gas chromatography/mass spectrometry (GC/MS); electron impact ionization of DMDS adducts gives an abundant molecular ion, and the cleavage between the methylthio-substituted carbons produces a set of fragment ions that serve to locate the original double-bond position in a monoenoic fatty acid ester. In 1985, Leonhardt and DeVilbiss [2], Dunkelblum et al. [3] and Shibahara et al. [4] separately reported that DMDS adducts could be prepared from mixtures of double-bond positional isomers of monoenoic acid esters and from mixtures of saturated and unsaturated esters from natural sources (bacterial lipids [2], pheromone gland lipids [3] and plant lipids [4]). Each research group, however, used different reaction conditions for preparing the DMDS adducts (e.g., reaction times and temperatures: 24 h at 40 °C [2]; overnight at 40 °C [3]; and 30 min at 35 °C [4]).
Procedures to form DMDS adducts are widely used. The Lipid Library [5] lists more than 70 publications regarding DMDS adducts. Our research group has been preparing DMDS adducts for ~2 decades [4, 6-17]. We recently developed an improved procedure that reduces the hazard to analysts from the DMDS fumes and substantially reduces the...