Development and validation of stable-isotope dilution liquid chromatography-tandem mass spectrometric method for...

A method for the quantification of progesterone (PROG) in human saliva using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) has been developed and validated. The saliva was deproteinized with acetonitrile, purified using a Strata™-X cartridge, and subjected to LC-ESI-MS/MS. Quantification was based on selected reaction monitoring, and deuterated PROG was used as the internal standard. This method allowed the reproducible (intra- and inter-assay relative standard deviations, <2.2%) and accurate (analytical recovery, 96.6-99.7%) quantification of the salivary PROG using a 400 μL sample, and the limit of quantification was 12.5 pg/mL. The developed method enabled detection of the variation in the salivary PROG concentrations of healthy volunteers during the menstrual cycle and measurement of the salivary concentrations of pregnant women. The method is expected to be an alternative to the blood PROG monitoring in clinical examinations, because saliva collection is easy, non-invasive and repeatable.