Simultaneous determination of tetrahydrocortisol and tetrahydrocortisone in human plasma and urine by stable isotope dilution mass spectrometry

A capillary gas chromatographic-mass spectrometric method for the simultaneous determination of tetrahydrocortisol (THF, 3 alpha,11 beta,17 alpha,21-tetrahydroxy-5 beta-pregnane-20-one), allo-tetrahydrocortisol (allo-THF, 3 alpha,11 beta,17 alpha,21-tetrahydroxy-5 alpha-pregnane-20-one) and tetrahydrocortisone (THE, 3 alpha,17 alpha,21-trihydroxy-5 beta-pregnane-11,20-dione) in human plasma and urine is described. [1,2,3,4,5-H-2(5)]THF (THF-d(5)), allo-[1,2,3,4,5-H-2(5)]THF (allo-THF-d(5)) and [1,2,3,4,5-H-2(5)]THE (THE-d(5)) were used as internal standards. A double derivatization (bismethylenedioxypentafluoropropionate, BMD-PFP) made possible the separation of the three tetrahydrocorticoids with good gas chromatographic behavior. Quantitation was carried out by selected-ion monitoring of the characteristic fragment ions ([M-30](+)) of the BMD-PFP derivatives of THF, allo-THF and THE. The sensitivity, specificity, precision and accuracy of the method were demonstrated to be satisfactory for measuring low concentrations of THF, allo-THF and THE in human plasma and urine. (C) 1998 Elsevier Science B.V.