Development of a liquid chromatography–tandem mass spectrometry method for the determination of 23 endogenous steroids in small quantities of primate urine

Abstract

A quantitative method using liquid chromatography–tandem mass spectrometry (LC–MS–MS) was developed for the simultaneous determination of 23 endogenous steroids in primate urine. The introduced method includes estrone, pregnandiol, cortisol, testosterone and several human urinary glucocorticoid and androgen metabolites. As the method is intended for the analysis of steroid hormones in behavioral studies on wild-living primates, it was adapted for a sample volume of 200 μL urine. The sample preparation consisted of an enzymatic hydrolysis of steroid glucuronides using β-glucuronidase from E. coli followed by a solvolytic cleavage of steroid sulfates employing sulfuric acid/ethyl acetate. The extraction of steroids from urine was optimized with respect to pH during extraction, type of ether and the amount of enzyme necessary for complete hydrolysis of glucuronides. The recovery of steroids spiked into urine before hydrolysis was 58.9–103.7% with an intra-day precision of 2.7–14.3% and an inter-day precision of 2.9–14.8%. Detection limits ranged from 0.1–0.5 ng/mL. The reproducibility of the whole sample preparation process was also demonstrated for unspiked urine (CV 1.2–16.5%). The proportion of steroid hormone excreted as sulfate was determined for 21 steroids in chimpanzee urine. The solvolysis proved to be essential for all investigated steroids except for pregnandiol, tetrahydrocortisol and tetrahydrocortisone, which were found to be less then 10% in the solvolysis fraction.