Determination of fluorescent diamidines in plasma of experimental animals by high-performance liquid chromatography

The fluorescent diamidines (E)-2,2'-vinylenedi-1-benzo [b] furane-5-carboxamidine dihydrochloride (I) and 2-[2-(6-amidinoindole-2-yl)-(E)-vinyl]-1-benzofurane-5-ca rbo xamidine dihydrochloride (II) were determined in the plasma of experimental animals by high-performance liquid chromatography with a mobile phase of methanol-water (60:40, v/v) containing 0.005 M octanesulphonic acid and 0.003 M dimethyloctylamine. Samples were prepared by precipitation of plasma proteins with methanol-perchloric acid. Quantitation was performed by measuring the peak heights after monitoring the native fluorescence. The assay was linear over the range 5-750 ng/ml for I and 5-500 ng/ml for II, with limits of determination of 2.5 ng/ml for I and 1.5 ng/ml for II. Coefficients of variation were below 10% at all concentrations studied.