Drug monitoring of etoposide (VP16-213). I. A combined method of liquid chromatography and mass spectrometry.

Drug monitoring is performed by means of sample extraction, sample purification by high-performance liquid chromatography (HPLC), and sample detection by time-of-flight mass spectrometry. This mass spectrometry utilizing 252Cf fission fragment-induced ionization and desorption of nonvolatile compounds is suitable as a universal, nondestructive detector in HPLC. Liquid chromatography and mass spectrometry are combined, so that mass analysis can be operated online and offline to the fractional sampling of the effluent and the samples can still be recovered. As an alternative to HPLC separation, samples can be purified by thin-layer chromatography (TLC), resulting an offline TLC + MS combination. Preliminary pharmacokinetic data for etoposide (VP16-213) together with calibration data are presented, and are discussed with reference to the sensitivity and detection limit of the new experimental method.