High-performance liquid chromatography with amperometric detection appliedto the determination of the beta-blocker oxprenolol in urine and pharmaceuticals

A rapid and simple high performance liquid chromatographic (HPLC) method wi th amperometric detection has been developed for the quantitative determina tion of oxprenolol in human urine and pharmaceuticals. The chromatographic method was performed at (25 +/- 0.2)degrees C on a reversed-phase column (S upelcosil ABZ + Plus) with a mobile phase of acetonitrile-water (30:70, v/v ) containing 4 mM acetate buffer pH = 4.4 and with a flow rate of 1 mL/min. The amperometric detector equipped with a glassy carbon electrode was opera ted at +1300 mV versus Ag/AgCl in direct current mode. A simple solid phase (SPE) extraction method was used as clean-up procedure, obtaining recoveri es greater than 90% for spiked urine samples. The method was found to be ac curate, precise, and sensitive enough to determine free oxprenolol in human urine samples, which would allow its application to doping analysis. The m ethod developed allowed the analysis of urine samples obtained from a patie nt under treatment with oxprenolol, and to its determination in the pharmac eutical formulation Transitensin (oxprenolol 80 mg + chlortalidone 10 mg).