Determination of oxpentifylline and three metabolites in plasma by automated capillary gas chromatography using nitrogen-selective detection.

A procedure is described for the simultaneous determination of oxpentifylline and three metabolites in plasma by capillary gas chromatography. Plasma samples are acidified and extracted with chloroform. The carboxylic acid compounds are converted to their methyl esters and the hydroxylated metabolites to their O-trifluoroacetates prior to analysis by capillary gas chromatography using nitrogen-selective detection. The detection limits for the compounds are 5 ng/ml and the assay has been applied to the analysis of plasma from volunteer trials after oral administration of oxpentifylline.