Determination of Simvastatin by Voltammetry Method at Screen-Printed Electrode Modified by Graphene Oxide Nanosheets and Sodium Dodecyl Sulfate

An accurate, rapid, simple, and novel technique was developed to determine simvastatin (SMV). In this research, a screen-printed electrode (SPE) was deposited with graphene oxide (GO) and sodium dodecyl sulfate (SDS), respectively. For the first time, the handmade modified SPE measured the SMV by differential pulse voltammetry (DPV) with high sensitivity and selectivity. The results of cyclic voltammetry indicated the oxidation irreversible process of SMV. Various parameters (pH, concentration, scan rate, support electrolyte) were performed to optimize the conditions for the determination of SMV. Under the optimum experiment condition of 0.1 M KNO3 as support electrolyte and pH 7.0, the linear range was achieved for SMV concentration from 1.8 to 36.6 µM with a limit of detection (LOD), and a limit of quantitation (LOQ) of 0.06 and 1.8 µM, respectively. The proposed method was successfully utilized to determine SMV in tablets and urine samples with a satisfactory recovery in the range of 96.2 to 103.3%.

Degradation of gestodene (GES)–17α-ethinylestradiol (EE2) mixture by electrochemical oxidation

Evidence of the negative effects of several pharmaceutical molecules, such as hormones and steroids, on the environment can be observed throughout the world. This paper presents the results of the anodic oxidation of the mixture of gestodene steroid hormones and 17 α-ethinylestradiol present in aqueous medium. The tests were conducted in an undivided cell containing a working volume of 50 mL, using a Na2SO4 solution as support electrolyte and boron-doped diamond electrodes. The experiments were adjusted to the structure of a 33 factorial design. The evaluated factors were: support electrolyte concentration (0.02, 0.05, and 0.10 M), pH of the reaction media (2, 3, and 4), and current density (16, 32, and 48 mA cm−2). Under the optimum conditions (0.02 M Na2SO4, pH 4, and current density of 32 mA cm−2), the degradation of at least 93% of the initial concentration of gestodene and 17α-ethinylestradiol was reached in a reaction time of 5 and 10 min, respectively. The complete degradation of both molecules required 15 min of reaction. Under these conditions, the degradation profile of the pharmaceutical mixture as each one of the active ingredients, followed a pseudo-first order kinetic behavior (kmix = 0.0321, kGES = 0.4206, and kEE2 = 0.3209 min−1).