Rapid and sensitive analysis of vincristine in human plasma using on‐line extraction combined with liquid chromatography/tandem mass spectrometry

A simple and rapid method has been developed and validated for the quantitation of vincristine in human plasma by liquid chromatography/tandem mass spectrometry (LC/MS/MS) with atmospheric pressure chemical ionization using on‐line solid‐phase extraction. The method uses vinblastine as internal standard and the sample preparation is limited just to a plasma protein precipitation step. Further sample clean‐up is carried out on‐line through a perfusion column preceding an analytical phenyl LC column, the latter directly connected to the mass spectrometer. Quantitation is performed in multiple reaction monitoring mode using the transitions of m/z 825.3 → 765.3 and 811.3 → 751.3 for vincristine and vinblastine respectively. The assay was linear (r 2 ≥0.99) in a concentration range from 0.1 to 500 ng/mL. Carry‐over, measured on the experimental set‐up, was less than 0.04%. Recovery for vincristine and the internal standard was within 90–95%. The intra‐day and inter‐day assay precision ranged from 1.2% to 6.8% RSD while mean percentage deviation from nominal value ranged from 0.01% to 6.1%. The proposed assay was found suitable for pharmacokinetics investigations and clinical therapeutic drug monitoring especially in pediatric cancer patients. Copyright © 2008 John Wiley & Sons, Ltd.