Certification of steroid carbon isotope ratios in a freeze-dried human urine reference material / Ellaine Munton, Fong-Ha Liu, E. John Murby, D. Brynn Hibbert
- Drug Testing and Analysis 4 (2012) 12 (December), p. 928-933
- Special Issue: Stable isotope ratio analysis in sports anti‐doping
- PMID: 22544546
- DOI: 10.1002/dta.1366
An accurate method for the measurement of carbon isotope ratios of steroids in human urine has been developed at the National Measurement Institute, Australia (NMIA) for the certification of a freeze-dried human urine reference material (CRM NMIA MX005). The method measures δ(13)C values by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) analysis following hydrolysis, solvent extraction and high performance liquid chromatography (HPLC) purification. Reference δ(13)C values for testosterone metabolites etiocholanolone, androsterone, and endogenous reference compounds (ERCs) 11β-hydroxyandrosterone and pregnanediol were determined, as well as information δ(13)C values for testosterone, epitestosterone, 11-oxoetiocholanolone, and a range of differences (Δ(13)C) between testosterone metabolites and ERCs. The measurement uncertainty was rigorously evaluated with expanded uncertainties for the reference δ(13)C values between 1.1 and 1.6 ‰ at the 95% coverage level.