Characterization of sterols by gas chromatography-mass spectrometry of the trimethylsilyl ethers
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The utility of combined gas chromatography-mass spectrometry in the analysis and characterization of sterols has been explored. Methylene unit (MU) values and principal mass spectrometric data are presented for trimethylsilyl ethers of 28 sterols, including the major natural sterols. The diagnostic value of the fragmentation of trimethylsilyl ethers of Δ5-3 β-hydroxysteroids has been confirmed. Characteristic fragmentations of Δ4-3 β-trimethylsilyloxysteroids, and of Δ5,7-3 β-trimethylsilyloxysteroids were also found. Location of side-chain hydroxyl groups is facilitated by the α-cleavages typical of the trimethylsilyl ethers. Fragmentations of saturated sterols, and of Δ7, Δ8(9) and Δ(14) stenols, are less influenced by trimethylsilyl ether formation, but the derivatives still afford satisfactory mass spectra. The combination of gas chromatographic and mass spectrometric information allows positive identification of any of the sterols examined, whereas application of either technique alone may give inconclusive results.
KeywordsBase Peak Lanosterol Mass Spectrometric Data Desmosterol Trimethylsilyl Ether
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