High-performance liquid chromatographic assay of formycin A in plasma after solid-phase extraction

A new, simple and accurate high-performance liquid chromatography (HPLC) method for the determination of formycin A in plasma is presented. The samples were chromatographed on a LiChrosórb RP-18 column after purification using a Bakerbond SPE column. The mobile phase was methanol-0.067 M phosphate buffer, pH 4.20 (1:4, v/v) containing 0.005 M sodium hexanesulfonate. Azathioprine was applied as an internal standard. UV detection was carried out at 293 nm. The method was tested for linearity (over the range 0.1-9.0 micrograms/ml). The recovery was 91.89% (mean). The described method has been successfully applied to the quantitative determination of formycin A in plasma and should be useful for clinical and bioavailability investigations.