A rapid screening assay for measuring urinary androsterone and etiocholanolone delta C-13 (parts per thousand) values by gas chromatography/combustion/isotope ratio mass spectrometry

A gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) method is described and validated for measurement of delta C-13 values of the acetate derivatives of urinary etiocholanolone and androsterone, The an alysis was performed with only 2 mt, of urine. The sample preparation consi sted of deconjugation with beta -glucuronidase, solid phase extraction, and derivatization with acetic anhydride and pyridine. The within-assay precis ion of two quality control (QC) urine samples ranged from 0.5 to 2.1 CV%. T he between-assay precision in the same QC urines ranged from 1.7 to 3.4 CV% . Administration of testosterone enanthate to a subject resulted in a 6 par ts per thousand decrease in delta C-13 values from -25 parts per thousand ( baseline) to -31 parts per thousand. Two weeks after testosterone administr ation was discontinued, the delta C-13 values remained abnormally low while the urine testosterone/epitestosterone (T/E) ratio returned to less than 6 , This relatively simple method is useful for rapidly screening a large num ber of urine samples, including those with T/E: <6, Copyright (C) 2000 John Wiley & Sons, Ltd.