Electrochemical Sensor Based on Mn3O4-MnCo2O4-CNT Nanocatalyst Graphene Nanoplatelets for Trace Determination of Thioridazine in Biological and Pharmaceutical Samples

Abstract

In this paper, a mixed nano-catalyst of magnesium oxide (Mn3O4) and magnesium-cobalt oxide (MnCo2O4) was synthesized in the presence of carbon nanotubes (CNT) and was easily mixed with graphene nanoplatelet (GNP). The constructed nanocomposite (Mn3O4-MnCo2O4-CNT/GNP) was characterized using field emission scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray. As an application, a suspension of Mn3O4-MnCo2O4-CNT/GNP nanocomposite was prepared and drop-casted on a screen-printed electrode (SPE) for using as a portable electrochemical sensor for the determination of thioridazine (TR) with the highest catalytic effect, sensitivity, and selectivity. The differential pulse voltammetry response of the Mn3O4-MnCo2O4-CNT/GNP-modified SPE was linear with TR concentration in the range of 0.02– $50.0~ {\mu }$ mol $\text{L}^{- {1}}$ under optimized conditions (phosphate buffer, pH 7.0; drop-casting volume $20~\mu \text{L}$ ; nano-catalyst 200 $\mu \text{L}$ ; and accumulation time 80 s), with a detection limit of 1.5 nmol $\text{L}^{- {1}}$ ( $S/N = 3$ ). The fabricated electrochemical sensor showed a selective amperometry response toward TR concentration among other interfering species. Relative standard deviation (RSD) at two different concentrations of TR, (10.0 and 40.0 $\mu $ mol $\text{L}^{- {1}}$ ) was, respectively, 4.9% and 4.5%, exhibited good reproducibility. Finally, the proposed sensor was successfully applied for the determination of the TR in urine, serum, and a TR pharmaceutical formulation.