RESUMO
RATIONALE: Two new certified reference materials (CRMs) have been prepared providing three steroids certified for stable carbon isotope delta values, δ(13 C) . These materials have been designed to assist anti-doping laboratories in validating their calibration method or to be employed as calibrant for stable carbon isotope measurements of Boldenone, Boldenone Metabolite 1 and Formestane. These CRMs will allow for accurate and traceable analysis in compliance with World Anti-Doping Agency (WADA) Technical Document TD2021IRMS. METHODS: Certification was performed using an elemental analyser-isotope ratio mass spectrometry (EA-IRMS) primary reference method on the bulk carbon isotope ratios of nominally pure steroid starting materials. EA-IRMS analyses were carried out on a Flash EA Isolink CN coupled via a Conflo IV to a Delta V plus mass spectrometer. Confirmation analysis was performed by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) using a Trace 1310 GC coupled to a Delta V plus mass spectrometer via GC Isolink II. RESULTS: Based on the EA-IRMS analysis, the materials were certified with δ(13 C) values of -30.38 (Boldenone), -29.71 (Boldenone Metabolite 1) and 30.71 (Formestane). Noting that the assumption of 100% purity in the starting materials has the potential to introduce bias, this was investigated using GC-C-IRMS analysis and theoretical modelling based on purity assessment data. CONCLUSIONS: Careful application of this theoretical model was shown to provide reasonable estimates of uncertainty while avoiding the introduction of errors associated with analyte-specific fractionation during GC-C-IRMS analysis.