Sources of plant sterol contaminants encountered in low level steroid analysis.

During development of an analytical method to characterize ligands to new members of the steroid hormone receptor superfamily, a persistant contaminant profile was observed during gas chromatographic analysis of reagent blanks. Mass spectrometric analysis identified three of the contaminant peaks as cholesterol and the plant sterols stigmasterol and sitosterol. Laboratory articles made of natural rubber, i.e. pipette fillers and latex gloves, were found to be the source of these and other compounds in the reagent blank profile.