Voltammetric Behavior of Gestodene Using Square-Wave Technique. Determination in Oral Contraceptives

Abstract

The behavior of gestodene (GTD) was studied by square‐wave techniques, leading to two methods for its determination in aqueous samples and pharmaceutical formulations. The application of the square‐wave mode shows the determination of GTD between 2×10–7 and 3×10–6M at –1.30 V. GTD gave an adsorptive stripping voltammetric peak at the hanging mercury drop electrode at –1.30 V using an accumulation potential of –0.80 V. The effect of experimental parameters that affected this determination are discussed. The stripping technique proved to be more GTD sensitive, yielding signals seven times larger than those obtained by applying a square‐wave scan without previous accumulation. The calibration plot determined by stripping voltammetry was linear in the range between 3×10–8 M and 1×10–6 M by stripping mode. The relative standard deviations for concentration levels of GTD as low as 7.5×10–7 M obtained with the square‐wave technique was 2.3% (n=12) and for 1.5×10–7 M with stripping square‐wave was 2.3% (n=12). The proposed method was applied to the determination of gestodene in four different Spanish commercial low‐dose oral contraceptives with good recoveries in respect to the labelled values.