Determination of a new thymidine phosphorylase inhibitor, TPI, in dog and rat plasma by reversed-phase ion-pair high-performance liquid chromatography

A high-performance liquid chromatographic method for the determination of a new thymidine phosphorylase inhibitor, TPI, in dog and rat plasma is described. TPI was isolated from biological samples by solid-phase extraction on Bond Elut PRS columns. Chromatographic separation was achieved on a C18 column using a mobile phase consisting of acetonitrile–10 mM acetate buffer (pH 4.3) including hexanesulfonate, with UV detection at 276 nm. This method has been validated across the range of 50–50 000 ng/ml using a 0.1-ml plasma volume. The mean recoveries from spiked plasma were 93% for dog and 94% for rat, respectively. The accuracy, precision and specificity of the method were demonstrated to be acceptable, and it was applied to the toxicokinetic study of TPI in rats.