A Rapid Isocratic HPLC Assay of Suramin (NSC 34936) in Human Plasma

A reversed-phase, isocratic HPLC method was developed for the quantitation of suramin in plasma. The addition of acetonitrile containing the ion pairing agent tetrabutylammonium phosphate (0.05 M) and an internal standard, 2-naphthol, served to precipitate the protein of plasma and concurrently extract suramin into acetonitrile as the ion pair. After centrifugation, the supernatant was diluted with an equal volume of ammonium acetate buffer (0.01 M, pH 6.5) and an aliquot was injected on column. Chromatography was carried out on a 4 μm Nova-Pak C18 radial compression column (5 mm × 100 mm) using a water-methanol (51:49, v/v) mobile phase containing 0.01 M ammonium acetate buffer (pH 6.5) and 0.001 M tetrabutylammonium phosphate with detection by UV absorption at 238 nm. The run time for a single plasma sample was less than 10 min. Employing 25 μl of plasma, concentrations of suramin in the range 50–500 μg/ml were quantitated.