title: Determination of free and deconjugated testosterone and epitestosterone in urine using SPME and LC-MS/MS.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Chemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada.
authors.forename: Yanwei
authors.initials: Y
authors.lastname: Zhan
authors.forename: Florin M
authors.initials: FM
authors.lastname: Musteata
authors.forename: Fabien A
authors.initials: FA
authors.lastname: Basset
authors.forename: Janusz
authors.initials: J
authors.lastname: Pawliszyn
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004129:Dimethylpolysiloxanes; D004845:Epitestosterone / Q000302:isolation & purification / Q000652:urine*; D020719:Glucuronides / Q000378:metabolism; D006801:Humans; D057230:Limit of Detection; D008567:Membranes, Artificial; D052617:Solid Phase Microextraction / Q000379:methods*; D021241:Spectrometry, Mass, Electrospray Ionization; D013237:Stereoisomerism; D053719:Tandem Mass Spectrometry; D013739:Testosterone / Q000302:isolation & purification / Q000652:urine*
chemical_list: D004129:Dimethylpolysiloxanes; D020719:Glucuronides; D008567:Membranes, Artificial; D013739:Testosterone; D004845:Epitestosterone