Determination of vincristine in mouse plasma and brain tissues by liquid chromatography–electrospray mass spectrometry

Vincristine is an anticancer agent that continues to be examined in preclinical models even though it is used in a variety of human neoplastic disorders. We developed a sensitive liquid chromatography–mass spectrometry (LC–MS) method for the determination of vincristine in plasma and in brain tissues that would support investigations on drug distribution into tissues in animal models. The procedure required only a small sample volume (10 μl) of plasma, which circumvented a limitation of most other assays that were developed for human samples. A solid-phase extraction procedure was employed that enabled the eluent to be directly injected onto a reversed-phase chromatographic HPLC system using positive electrospray ionization followed by mass spectrometric detection. The extraction recoveries of vincristine were 57 and 60% from plasma and brain tissues, respectively. The mobile phase consisted of methanol and 15 mM ammonium acetate in 0.02% formic acid (70:30) that was pumped at 0.2 ml/min to yield retention times of 1.6 and 1.8 min for vincristine and vinblastine, the internal standard, respectively. The method was validated at vincristine plasma concentrations from 0.01 to 2 μg/ml, and from 0.01 to 1 μg/g in brain tissue. The advantage of the method enabled the quantitation of vincristine in multiple plasma samples obtained from a single mouse, which permitted the accurate estimation of its pharmacokinetic properties.