A mass spectrometric approach for the study of the metabolism of clomiphene, tamoxifen and toremifene by liquid chromatography time-of-flight spectroscopy

In this paper, we discuss the capabilities of liquid chromatography coupled to mass spectrometry with a time-of-flight system with accurate mass measurement for the detection and characterisation of drug metabolites in biological samples for anti-doping purpose. Urinary excretion samples of three selective oestrogen receptor modulators (SERMs) with a common triphenylethylene structure: clomiphene, toremifene and tamoxifen, obtained after oral administration of a single dose of each drug, were analysed using a time-of-flight system, after automatic tuning and calibration of the equipment, in positive full scan mode using an electrospray ionisation source. Following this approach we detected most of all significant metabolites reported by others and postulated new metabolites, especially for toremifene, have been characterised: N-demethyl-3-hydroxy-4-methoxy-toremifene and 3-hydroxy-4-methoxy-toremifene; in addtion to this, in the urinary excretion samples of toremifene some metabolites, without the characteristic chlorine isotope pattern, discarded in previous studies, that are also metabolites of tamoxifen, were identified. The tack of certified reference materials does not allow an accurate determination of the limit of detection (LODs) of all metabolites; however, an estimation taking into account the response factor of similar compounds allows to estimate that all metabolites are clearly detectable in a range of concentration comprised between 10 ng mL(-1) and 30 ng mL(-1).