title: Simultaneous determination of endogenous and stable isotope-labelled 6beta-hydroxycortisols in human urine by stable isotope dilution mass spectrometry.
abstract: This study describes a capillary GC-MS method for the simultaneous determination of endogenous 6beta-hydroxycortisol (6beta-OHF) and its stable isotope-labelled analogue, 6beta-hydroxy-[1,1,19,19,19-2H(5)]cortisol (6beta-OHF-2H(5)), in human urine. 6beta-Hydroxy-[1,2,4,19-13C(4),1,1,19,19,19-2H(5)]cortisol (cortisol-13C(4),(2)H(5)) was used as an analytical internal standard. The methoxime trimethylsilyl ether (MO-TMS) derivatization was employed for the GC-MS analysis of 6beta-OHF. Quantitation was carried out by selected-ion monitoring (SIM) of the characteristic fragment ion ([M-31](+.)) of the MO-TMS derivative of 6beta-OHF. The sensitivity limit of the present GC-MS-SIM method was found to be 25 pg per injection for 6beta-OHF (S/N ratio=5.6). The within-day reproducibility in the amounts of unlabelled and labelled 6beta-OHFs determined were in good agreement with the actual amounts added, the relative errors being less than 5.30%. The inter-assay RSDs were less than 4.95% for unlabelled and labelled 6beta-OHFs.
authors.affiliation: School of Pharmacy, Tokyo University of Pharmacy and Life Science, 192-0392 Tokyo, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Suzuki
authors.forename: Hiromi
authors.initials: H
authors.lastname: Shibasaki
authors.forename: Yasuji
authors.initials: Y
authors.lastname: Kasuya
authors.forename: Takashi
authors.initials: T
authors.lastname: Furuta
mesh_terms: D002138:Calibration; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D006854:Hydrocortisone / Q000031:analogs & derivatives* / Q000652:urine*; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: C001380:6 beta-hydroxycortisol; D006854:Hydrocortisone