DETERMINATION OF PROGUANIL AND METABOLITES IN SMALL SAMPLE VOLUMES OFWHOLE-BLOOD STORED ON FILTER-PAPER BY HIGHPERFORMANCE LIQUID-CHROMATOGRAPHY

A method is reported for the determination of proguanil and its two me tabolites cycloguanil and 4-chlorophenylbiguanide in whole blood and p lasma samples obtained by thumbprick and stored dry on filter paper. T he sample preparation involves liquid extraction from the filter paper and subsequent solid-phase extraction using C-8 Bond-Elut cartridges. Separation and quantification is by a previously reported ion-pairing high-performance liquid chromatographic system with ODS Hypersil as s tationary phase and an 50:50 acetonitrile-pH 2 phosphate buffer mobile phase containing 200 mM sodium dodecylsulphate as ion-pairing agent. The analytical characteristics of the method are reported. Representat ive concentrations are shown as a function of time from a human subjec t after ingestion of a single 200-mg dose of proguanil hydrochloride. Typical ranges of concentration detected by the proposed method in hum an subjects were proguanil 12-900 ng/ml, cycloguanil 16-44 ng/ml and 4 -chlorophenylbiguanide 1.5-10 ng/ml in whole blood.