Improved method for the simultaneous determination of proguanil and its metabolites by high-performance liquid chromatography and solid-phase extraction of 100-microl capillary blood samples dried on sampling paper.

An improved method is presented for the determination of proguanil, cycloguanil and 4-chlorophenylbiguanide in 100-microl capillary blood samples applied to sampling paper. This method also utilises a solid-phase extraction technique and high-performance liquid chromatography. Different kinds of sampling paper, such as ion-exchange and cellulose sampling paper were tested. The best elution recovery (70-80%) was obtained after treatment of cellulose sampling paper with a quaternary ammonium compound. The limit of determination was 50 nmol/l for cycloguanil and 4-chlorophenylbiguanide and 125 nmol/l for proguanil using 100 microl capillary blood. The stability of the analytes and elution performance from sampling paper was validated at different temperature and storage time. Venous blood and capillary blood concentrations of proguanil and metabolites were found to be similar.