Abstract
Synthetic mixtures of C40 to C47 sterol esters in groups of 7 esters were effectively separated and analyzed by capillary gas chromatography-mass spectrometry. Ammonia chemical ionization of all 20 sterol esters analyzed at a source block temperature of 120 C yielded (M+NH4)+ and (M+H-RCO2H)+ ions of high abundance or as base peak, thereby indirectly indicating the molecular weights of the ester and the sterol and acid moieties. Ammonia CI spectra of all esters containing a Δ5-sterol moiety exhibited in addition to the above 2 ions an M+NH4-RCO2 H fragment. At a source block temperature of 150 C, M+H-RCO2 H fragment was the base peak for all esters, and there was little or no indication of an (M+NH4)+ adduct ion. Protonated molecules were not observed for any esters analyzed by methane or isobutane CI. Molecular ions of 3–14% intensity were obtained for only 3 of the esters analyzed by electron impact; they contained a Δ7-bond in the sterol nucleus, and the acid moiety was either saturated normal or branched chain or contained a single double bond. The base peak was a function of both the acid and sterol moieties of the sterol ester. The esters containing both saturated straight chain acid and saturated sterol moieties exhibited a base peak at m/z 215. The Δ5-sterol esters with saturated branched or straight chain acid moieties exhibited base peaks at M-RCO2 H. Other ions also were of diagnostic value.
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McKibben, G.H., Thompson, M.J., Parrott, W.L.; Thompson, A.C., and Lusby, W.R., manuscript in preparation.
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Lusby, W.R., Thompson, M.J. & Kochansky, J. Analysis of sterol esters by capillary gas chromatography-electron impact and chemical lonization-mass spectrometry. Lipids 19, 888–901 (1984). https://doi.org/10.1007/BF02534520
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DOI: https://doi.org/10.1007/BF02534520