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

A capillary gas chromatographic assay for the determination of oxpentifylline and four hydroxylated metabolites is described. Oxpentifylline, metabolites and internal standards are extracted from basified plasma or urine with chloroform and the metabolites are converted to their O-trifluoroacetates before analysis by capillary gas chromatography using nitrogen-selective detection. A high throughput of samples is achieved by use of an autosampler and a split injection technique which allows the samples to be analysed isothermally. The detection limits of the compounds are in the range 2-10 ng/ml for plasma and 0.1-0.2 microgram/ml for urine. The assay has been applied to the analysis of plasma and urine samples after the oral administration of oxpentifylline.