Voltammetric study of danazol and its determination in capsules and spiked biological fluids

The voltammetric behaviour of danazol DZ (antigonadotropin) was studied using cyclic voltammetry, direct current, differential pulse polarography (DPP) and alternating current polarography. Danazol exhibited irreversible cathodic waves over the pH range of 1-5 in Britton Robinson buffers. At pH 1 (the analytical pH), a well-defined wave with E1/2 of −1.04 V versus Ag/AgCl reference electrode was obtained. The diffusion current constant (Id) was 4.8 ± 0.14 μA.L.m mole−1 and the current-concentration plot was rectilinear over the range from 5 × 10−6 to 1 × 10−4 M with correlation coefficient (n = 11) of 0.995. The calculated detection limit was 1 × 10−6 M using the DPP mode. The wave was characterized as being irreversible, diffusion-controlled although adsorption phenomenon played a limited role in the electrode process. The proposed method was applied to commercial capsules and the average percentage recovery was in agreement with that obtained by the official USP method. The method was extended to the in vitro determination of DZ in spiked human urine and plasma samples, the percentage recoveries were 96 ± 4 and 97 ± 5, respectively. A proposal of the electrode reaction was postulated.