Determination of a natural (17β-estradiol) and a synthetic (17α-ethinylestradiol) hormones in pharmaceutical formulations and urine by adsorptive stripping voltammetry

Abstract

An efficient, fast and sensitive method for the determination of 17β-estradiol, (E2) and 17α-ethinylestradiol (EE2) in pharmaceutical formulations and in urine was developed and validated using a hanging mercury drop electrode (HMDE), screen printed carbon electrodes (SPCE), and screen printed carbon nanotube electrodes (SPCNTE). Both analytes are adsorbed on the working electrodes. To obtain sensitive and selective methods, the effects of various parameters such as pH, adsorption potential, and time (Eads, tads) were optimized. The optimum experimental conditions chosen for the two analytes were pH: 10.0; Eads: −0.60 and tads: 30 s, when HMDE was used. Under these conditions, one reduction signal was found at −1.31 V for E2 and two reduction signals at −0.23 V and −1.20 V for EE2. The detection limits (DLs) were found to be 0.3 μg L−1 for E2, 14.8 μg L−1 for EE2 at −0.23 V, and 9.7 μg L−1 for EE2 at −1.20 V. On the other hand, in screen printed electrodes E2 and EE2 present oxidation of the phenolic hydroxyl groups at 0.30, 0.31, 0.32, and 0.33 V (pH:10) with DLs of 242, 277; 182, and 191 μg L−1 for SPCE and SPCNTE, respectively. The method was successfully applied to the determination of these analytes in Primaquin® (E2), Gynera® (EE2), spiked urine (with EE2), and urine samples of women who used Tinelle® (EE2) as contraceptive drug.