IRMS detection of testosterone manipulated with 13C labeled standards in human urine by removing the labeled 13C

Isotope ratio mass spectrometry (IRMS) is applied to confirm testosterone (T) abuse by determining the carbon isotope ratios (delta C-13 value). However, C-13 labeled standards can be used to control the delta C-13 value and produce manipulated T which cannot be detected by the current method. A method was explored to remove the C-13 labeled atom at C-3 from the molecule of androsterone (Andro), the metabolite of T in urine, to produce the resultant (A-nor-5 alpha-androstane-2,17-dione, ANAD). The difference in delta C-13 values between Andro and ANAD (Delta delta C-13(Andro-ANAD), parts per thousand) would change significantly in case manipulated T is abused. Twenty-one volunteers administered T manipulated with different C-13 labeled standards. The collected urine samples were analyzed with the established method, and the maximum value of Delta delta C-13(Andro-ANAD) post ingestion ranged from 3.0 parts per thousand to 8.8 parts per thousand. Based on the population reference, the cut-off value of Delta delta C-13(Andro-ANAD) for positive result was suggested as 1.2 parts per thousand. The developed method could be used to detect T manipulated with 3-C-13 labeled standards. (C) 2014 Elsevier B.V. All rights reserved.