Steryl mass spectrometry

Kamm el al. (2001) analysed intact steryl esters in the presence of silylated sterols by online transfer from HPLC to a 15 m low-polarity high temperature GC column. Steryl esters were quantified against a cholesteryl laurate internal standard and identified by offline thin layer chromatography-gas chromatography-mass spectrometry. When esters of sitosterol, stigmasterol and campesterol with the major cocoa butter acids were measured in cocoa butters from South America, Asia and Africa, no differences were apparent between cocoa butters of different geographical origin, or between deodorized and non-deodorized butters. 

Gutierrez, A. del Rio, J.C. 2001. Gas chromatography/mass spectrometry demonstration of steryl glycosides in eucalypt wood, Kraft pulp and process liquids. Rapid Comm. Mass Spectrom. 15 2515-2520. 

To determine sterols, a portion of the total lipid extract is saponified using methanolic potassium hydroxide, and sterols subsequently recovered in 2 1 hex-ane/chloroform. The sterols are converted to the corresponding trimethylsilyl (TMS) ethers using bis-N,0-(trimethylsilyl)trifluoroacetamide, BSTFA, and analyzed by capillary GC and GC with mass spectrometry. Reviews of relative retention times and mass spectra for sterol TMS ethers have been published [e.g. 73]. In some cases, sterol acetates, rather than TMS ethers, are the derivatives prepared for GC. SiHca column chromatography of the total lipid extract may also be used instead of saponification to isolate the sterol fraction [74], or even sterol subclasses such as 4,4-dimethyl, 4-monomethyl and 4-desmethyl sterols [75], prior to derivatization. However, this approach only includes free sterols in the analysis, whereas by saponifying the total extract, sterols present as steryl esters are also detected. 

Wakeham, S. G. and Frew, N. M. (1982) Gas capillary gas chromatography-mass spectrometry of wax esters, steryl esters and triacylglycerols. Lipids, 17, 831-43. 

Schrick, K., Shiva, S., Arpin, J.C., Delimont, N., Isaac, G., Tamura, P. and Welti, R. (2012) Steryl glucoside and acyl steryl glucoside analysis of Arabidopsis seeds by electrospray ionization tandem mass spectrometry. Lipids 47,185-193. 

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