Determination of free and deconjugated testosterone and epitestosterone in urine using SPME and LC-MS/MS.

Background: A thin sheet of polydimethylsilosane membrane was used as an extraction phase for solid-phase microextraction. Compared with fiber or rod solid-phase microextraction geometries, the thin film exhibited much higher extraction capacity without sacrificing extraction time due to its higher area-to-volume ratio. The analytical method involved direct extraction of unconjugated testosterone (T) and epitestosterone (ET) followed by separation on a C18 column and detection by selected reaction monitoring in positive ionization mode.

Results: The limit of detection was 1 ng/l for both T and ET. After method validation, free (unconjugated) T and ET were extracted and quantified in real samples. Since T and ET are extensively metabolized, the proposed method was also applied to extract the steroids after enzymatic deconjugation of urinary-excreted steroid glucuronides.

Conclusion: The proposed method allows quantification of both conjugated and unconjugated steroids, and revealed that there was a change in the ratio of T to ET after enzymatic deconjugation, indicating different rates of metabolism.