HPLC-ICP-MS compared with radiochemical detection for metabolite profiling of 3H-bromohexine in rat urine and faeces

Abstract

³ H-Bromohexine was dosed to rats as a model compound to allow comparison of HPLC-ICP-MS detection on bromine to radiochemical detection in an in vivo drug metabolism study. Metabolite profiles were obtained in urine and faeces extracts. No influence of the methanol gradient on the bromine response was observed in the range of 18–75% methanol. The sensitivity obtained by HPLC-ICP-MS was almost two orders of magnitude better than on-line ³H radiochemical detection. For ICP-MS, the limit of detection was calculated to be 69 nM Br (injection volume 100 μl), corresponding to an absolute limit of detection of 1.3 ng of bromohexine on-column. This allowed ICP-MS detection of several minor metabolites that were not detected using radiochemical detection. Furthermore, metabolites that had lost the radioactive label were detected due to the bromine in the metabolites. As ICP-MS is also more selective than UV and molecular MS detection, it could thus be applied as an alternative detector in drug metabolism studies.