A highly dispersed multi-walled carbon nanotubes and poly(methyl orange) based electrochemical sensor for the determination of an anti-malarial drug: Amodiaquine.

A glassy carbon electrode modified with electrochemically polymerized methyl orange (PMO) and multi-walled carbon nanotubes (MWCNT) was developed. The morphologies of the fabricating materials (PMO and MWCNT) were investigated by field-emission scanning electron microscopy (FE-SEM). The designed sensor was used for the sensitive determination of amodiaquine (AQ), an anti-malaria drug. AQ was developed as an alternative to chloroquine because of its activity against chloroquine-resistant Plasmodium falciparum (P. falciparum) parasites. The modified electrode was employed to study the electrochemical oxidation of AQ using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Under optimal experimental conditions, DPV exhibited a linear response in the concentration range from 1.0 × 10-7 to 3.5 × 10-6 mol L-1 with a limit of detection (LOD) of 8.9 × 10-8 mol L-1. Furthermore, the number of electrons and protons involved in the electrochemical study of AQ was also calculated and a plausible mechanism for the electro-oxidation of AQ was deduced. The developed sensor demonstrated analytical applicability as it was successfully employed to determine the drug AQ in pharmaceutical formulations and human urine samples.

Fabrication of highly sensitive gold nanourchins based electrochemical sensor for nanomolar determination of primaquine.

A gold nanourchins modified glassy carbon electrode (AuNu/GCE) was developed for the determination of antimalarial drug, primaquine (PQ). The surface of AuNu/GCE was characterized by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cyclic voltammetry (CV). EIS results indicated that the electron transfer process at AuNu/GCE was faster as compared to the bare electrode. The SEM and TEM image confirmed the presence and uniform dispersion of gold nanourchins on the GCE surface. Upon investigating the electrochemical behavior of PQ at AuNu/GCE, the developed sensor was found to exhibit high electrocatalytic activity towards the oxidation of PQ. Under optimal experimental conditions, the sensor showed fast and sensitive current response to PQ over a linear concentration range of 0.01-1µM and 0.001-1µM with a detection limit of 3.5nM and 0.9nM using differential pulse voltammetry (DPV) and square wave voltammetry (SWV), respectively. The AuNu/GCE showed good selectivity, reproducibility and stability. Further, the developed sensor was successfully applied to determine the drug in human urine samples and pharmaceutical formulations demonstrating its analytical applicability in clinical analysis as well as quality control. The proposed method thus provides a promising alternative in routine sensing of PQ as well as promotes the application of gold nanourchins in electrochemical sensors.