Hyphenation of reverse-phase HPLC and ICP-MS for metabolite profiling-application to a novel antituberculosis compound as a case study

In this study, a high- performance liquid chromatography ( HPLC) inductively coupled plasma ( ICP) mass spectrometry ( MS) method was developed intended for use in metabolism studies of bromine- containing drugs, administered to test animals ( or test persons). As a case study, the method was applied to a new antituberculosis compound, the brominecontaining diarylquinoline R207910. A method has been proposed to overcome the incompatibilities between the high organic solvent content ( 45% CH3OH and 45% CH3CN) used in the reverse- phase liquid chromatography ( LC) separation on one hand and the limitations of the ICP on the other hand. Therefore, several instrument modifications had to be made. For the introduction of the column effluent, a combination of a perfluoroalkoxy LC nebulizer with a PC3 Peltier- cooled inlet system ( operated at 2 C) was used. Additionally, the standard injector tube ( internal diameter 2 mm) was replaced by an injector tube with an internal diameter of 1 mm and to avoid carbon build- up on the interface cones and the torch, the nebulizer gas was admixed with 6% v/ v of oxygen. After optimization of the method, HPLC- ICP- MS was applied for metabolite profiling of faeces samples after dosing of C-14-radiolabelled R207910 to dogs and rats. To evaluate the method developed, the HPLC- ICP- MS results were compared with those of HPLC with UV spectrophotometric and C-14 radiochemical detection. As the HPLC- ICP- MS method gave rise to a higher selectivity than HPLC with UV detection and to a better detection limit ( 5 ng R207910) than the method with radiochemical detection ( 65 ng R207910), it can be concluded that ICP- MS can be used as a good alternative to the more traditional detection methods, even when a mobile phase with high organic solvent content has to be used in the LC separation.