Steryl Esters and Steroid Hormones

Although cholesteryl esters (CEs) play an important role in cholesterol metabolism, there are few reports on CE analysis by MS. The behavior of cholesteryl esters in ESI is very similar to that of TAGs, and thus NH4 [124,125] and Ag+ adducts [126] have been used for their analysis. Fragmentation of the adduct ions produces a characteristic ion of miz 369.35 corresponding to [cholesterol-HjO]. Other steryl esters behave similarly (e.g., estrone esters [127]). With APPI, the [M-l-H-H20]+ ions are the most prominent ones [121]. 

Steroids are more polar than sterols, and can be analyzed by ESI and APCI without derivatization [128], albeit derivatization increases the sensitivity of detection [115,129]. 

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