Determination of 7-dehydrocholesterol in human skin by high-performance liquid chromatography.

A two-stage chromatographic procedure has been devised for the measurement of 7-dehydrocholesterol in human skin. Extracts containing ergosterol as internal standard underwent preparative chromatography on a Spherisorb S5W column using hexane-1% isopropanol as solvent, and an eluted fraction was analysed with an Ultrasphere 5-microns ODS column with methanol-tetrahydrofuran-17.5 mM KH2PO4 (95:1:4, v/v) as solvent and using an amperometric detector at 1.7 V. 7-Dehydrocholesterol could be reliably assayed in human skin samples as small as 5 mm in diameter. In hospital patients skin 7-dehydrocholesterol concentrations ranged from 12 to 81 micrograms/g dry weight.