Analysis of cholesterol, cholesterol-5,6-epoxides and cholestane-3 beta,5 alpha,6 beta-triol in nipple aspirates of human breast fluid by gas chromatography/mass spectrometry.

A method has been developed for the quantitative determination of cholesterol and three of its major oxidative metabolites (the 5 alpha,6 alpha-epoxide, the 3 beta,5 alpha,6 beta-triol, and the 5 beta,6 beta-epoxide) in a single sample of human breast fluid (2-50 microliters), using gas chromatography/mass spectrometry with selected ion monitoring. High specificity and reliable quantification is achieved by the use of the inverse stable isotope dilution method, employing deuterium-labeled variants of the compounds as internal standards.