Solid-phase extraction of vinblastine and vincristine from plasma and urine: variable drug recoveries due to non-reproducible column packings.

A sensitive and selective high-performance liquid chromatographic (HPLC) method for the determination of vinblastine and vincristine in plasma and urine is described. The drugs are isolated from 1.0 ml of the biological fluid with a solid-phase extraction column (Bond-Elut Diol). The HPLC method was combined with electrochemical detection at +850 mV versus an Ag/AgCl reference electrode. The detection limit is 100 pg for vinblastine and 250 pg for vincristine with a signal-to-noise ratio of 3, which permits the determination of these compounds in biological fluids at the nanogram level. Evaluation of the isolation method revealed that the drug recoveries and the reproducibility of the extraction procedure depend on the batch number of the solid-phase extraction column used.