TopCount coupled to ultra-performance liquid chromatography for the profiling of radiolabeled drug metabolites in complex biological samples

The recent commercial availability of small particle packed columns (<2 μm) and associated instrumentation capable of withstanding the high pressures of such columns, has lead to an increase in the application of so called ultra-performance liquid chromatography (UPLC). It has recently been shown that the improved efficiency, resolution and peak capacity of these columns, when coupled to mass spectrometry, provides particular benefit for the identification of drug metabolites in complex biological samples. In this work, the ability of TopCount, a microplate scintillation counter, to act as a suitable radiodetection system for ultra-performance liquid chromatography methods is tested. TopCount, has innumerable benefits over more traditional on-line radioactivity flow detection methods, when dealing with the narrow peak widths and small peak volumes associated with the enhanced efficiency of sub-2 μm columns. The system is tested for robustness and sensitivity, and then used to undertake successful metabolite profiling of actual samples, and the data compared to traditional HPLC with on-line radioactivity flow detector.