DETERMINATION OF A NEW POLYMER-BOUND PACLITAXEL DERIVATIVE (PNU-166945), FREE PACLITAXEL AND 7-EPIPACLITAXEL IN DOG PLASMA AND URINE BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH UV DETECTION

A sensitive and selective high-performance liquid chromatographic meth od for the determination of PNU 166945, a new polymer-bound paclitaxel derivative, free paclitaxel and 7-epipaclitaxel in dog plasma and uri ne has been developed. The method involves a solid-phase extraction of free paclitaxel and its possible degradation product 7-epipaclitaxel from plasma and urine, previously buffered with an equal volume of 0.0 5 M or 1 M KH2PO4 respectively, on 1-ml cyanopropyl columns. Cartridge s elution was performed with the mobile phase, 0.05 M (pH 4.6) monobas ic potassium phosphate-acetonitrile mixture (45:55, v/v). The samples were chromatographed on a reversed-phase octyl 4-mu m column with UV d etection at 229 nm. The retention times of paclitaxel and 7-epipaclita xel were about 14 and 22 min, respectively. Determination of total pac litaxel (free+polymer-bound) was performed after release of paclitaxel from the polymeric carrier by chemical hydrolysis at room temperature (22 degrees C) for 20 h. After addition of 0.5 mi of methanol-0.1 M K H2PO4 mixture (50:50, v/v, pH=7.5) to 0.5 mi of plasma or urine, pacli taxel was analysed as described above. PNU 166945 concentration was th en determined by subtraction of free from total paclitaxel. The linear ity, precision, accuracy and recovery of the method were evaluated. Th e limit of quantitation of the method was 5 ng/ml for biological fluid for paclitaxel and 7-epipaclitaxel and 20 ng/ml for PNU 166945 (as pa clitaxel equivalent). (C) 1998 Elsevier Science B.V.