High-performance liquid chromatography of proguanil, cycloguanil and 4-chlorophenylbiguanide using hydrophobic pairing ion and its application to serum assay

A high-performance liquid chromatographic separation of proguanil, cycloguanil and 4-chlorophenylbiguanide is reported using a hydrophobic stationary phase and lauryl sulphate as pairing ion. It is suggested, on the basis of the behaviour of phenylbenzoate as an undissociated solute and the variation of retention with lauryl sulphate and sodium ion concentrations that the mechanism of separation is one of ion exchange. The biguanides can be detected in serum at concentrations in the region of 60 ng ml-1 and preliminary results are presented to show the variation of proguanil in serum over a 24-h peroid following ingestion of 200 mg orally.