Determination of 3-(4′-methylbenzylidene)camphor and its metabolite 3-(4′-carboxybenzylidene)camphor in human semen by solid-phase extraction and liquid chromatography tandem mass spectrometry
An analytical method for the determination of the controversial UV filter 3-(4′-methylbenzylidene)camphor (MBC) and its metabolite 3-(4′-carboxybenzylidene)camphor (CBC) in human semen is presented. The method is based on the simultaneous hydrolysis of phase II conjugates and protein precipitation, followed by solid-phase extraction (SPE) and liquid chromatography tandem mass spectrometry (LC-MS/MS) detection. The proposed method was validated by analyzing spiked analyte-free human semen samples. Matrix-matched calibration using an analyte-free semen pool was employed. Satisfactory recoveries (92–114%) were obtained using this calibration methodology, thus showing the accuracy of the proposed method. The limits of detection were at the low μg L−1 level (1 and 2 μg L−1 for MBC and CBC, respectively) and the intra- and inter-day precision, expressed as relative standard deviation, were in the range of 6–9% and 7–14%, respectively, depending on the analyte and the concentration level. The method was finally applied to the analysis of semen samples from two volunteers who topically applied a laboratory-made sunscreen cream containing MBC. Similar kinetic profiles performed during 72 hours were obtained for both volunteers. From this study it can be assumed that more than three days is necessary to completely metabolize or eject this UV filter.