Sterols in Recent Marine Sediments I GC/MS Analysis of Major Sterols

A total of 18 different sterols extracted from marine sediments were identified by capillary gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). Identification of the sterols was achieved by analyzing GC retention time, interpreting MS data and comparing the mass spectra with those of commercial compounds or with published data. The identities of the sterols observed are listed in Table 1. Mass spectral data of the sterol trimethylsilyl ether derivatives are presented in Table 2 and Fig. s 4-8. The mass spectra of these sterol trimethylsilyl ether derivatives display characteristic peaks that can be used as diagnostics. The most important base peak at m/z129 and ion [M-129]+ can serve to distinguish △5-sterols from other sterols. The strongest characteristics of 5a-stanols are the presence of an intense peak at m/z215 and of a base peak at m/z75. The △22-sterols easily lose their side chain. In addition to elimination of the side chain with the loss of two hydrogen atoms [M-SC-2H]+ at m/z345, these derivatives show an intense [M-SC-ROH]+ peak at m/z257. The fragment at m/z374 can be considered as characteristic of the △22 unsaturated system. The △5,22-sterols also show a strong tendency to lose the unsaturated side chain and show an intense [M-SC-ROH]+ peak at m/z255. These sterols have the most important base peaks at m/z129 and ion [M-129]+ that are typical of △5-sterols