Determination of salivary 17-ketosteroid sulfates using liquid chromatography-electrospray ionization-mass...

A simple and sensitive liquid chromatography-electrospray ionization-mass spectrometric (LC-ESI-MS) method for the simultaneous quantification of representative 17-ketosteroid sulfates, dehydroepiandrosterone sulfate (DHEAS), androsterone sulfate and epiandrosterone sulfate, in human saliva has been developed and validated. The saliva was deproteinized with acetonitrile, purified using a solid-phase extraction cartridge and subjected to LC-MS. Deuterium-labeled DHEAS was used as the internal standard and quantification was based on the selected ion monitoring (SIM) mode of each deprotonated molecule. This method allowed the reproducible and accurate quantification of the salivary sulfates using a 100-microl sample; the intra- and inter-assay coefficients of variation were below 6.8 and 6.3%, respectively, and the % accuracy values were quantitative for all the sulfates. The limits of quantitation for all the sulfates were 100 pg/ml. No significant matrix effect or change in the measured value by freeze/thaw repetitions was observed. The developed method was applied to clinical studies, and produced satisfactory results.