Highly sensitive liquid chromatography-electrospray mass spectrometry (LC-MS) method for the determination of etoposide levels in human serum and plasma

Etoposide is one of the most commonly used antineoplastic agents. A highly sensitive liquid chromatography-electrospray mass spectrometry (LC-MS) meth od was developed for the determination of etoposide in human serum and plas ma. Etoposide was extracted with chloroform and extracts were reconstituted in acetonitrile followed by the evaporation of chloroform with nitrogen ga s. Etoposide was separated using Lichospher 100 RP-18 (5 mu m) column (250 mm x 4 mm) with the mobile phase of acetonitrile-water containing 0.1% acet ic acid (45/55, v/v) at flow-rate of 0.5 ml/min. Selected-ion monitoring (S IM) mode was performed on m/z 589 (positive ion mode) using a fragmentor of 75 V. Good linearity (r > 0.9965) was observed between concentrations of 0 .0125-5 mu M in 200 mu l serum and 0.01-10 mu M in 100 mu l plasma. Intra- and inter-assay variabilities were less than 7% and the lowest detection li mit of etoposide was 0.005 mu M in both serum and plasma at a signal-to-noi se ratio of similar to 4. The etoposide concentrations in four cancer patie nts treated with etoposide are also presented to demonstrate the clinical u tility of this new method, which should aid the pharmacokinetically guided use of etoposide in clinical settings. (C) 2000 Elsevier Science BN. All ri ghts reserved.