[en] Graphical abstract: Multi-walled carbon nanotubes paste electrode has been successfully used for the oxidation of FUR in BR buffer solution (pH = 5.0). Based on the study, influence of several physico-chemical parameters like potential scan rate, pH and concentration were investigated. Highlights: ► CNTPE has been successfully used for the electro-oxidation of FUR. ► Cyclic and differential-pulse voltammetric techniques are used. ► Effects of E_pa, I_pa and k⁰ have been discussed. ► DPV method was developed for the determination of FUR. - Abstract: Electrochemical oxidation of loop diuretic furosemide (4-chloro-2-(furan-2-ylmethylamino)-5-sulfamoylbenzoic acid) was studied in 5.0 pH with 0.04 M Britton–Robinson buffer as supporting electrolyte at 25 ± 0.1 °C at a multi-walled carbon nanotubes-paraffin oil paste electrode (CNTPE) using cyclic and differential-pulse voltammetric (DPV) techniques. The electrochemical process was observed to be adsorption controlled, irreversible and involving two-electron oxidation. Effects of anodic peak potential (E_pa), anodic peak current (I_pa) and heterogeneous rate constant (k⁰) have been discussed. Under optimal conditions, the peak current was proportional to furosemide concentration in the range of 8.0 × 10⁻⁶ to 2.0 × 10⁻⁴ M with a detection limit of 2.9 × 10⁻⁷ M by differential pulse voltammetry. A differential pulse voltammetric method with good precision and accuracy was developed for the determination of furosemide in pharmaceutical formulations and urine as a real sample.

[en] Highlights: • Highly sensitive gold nanoparticles/graphene modified glassy carbon electrode (AuNPs/Gr/GCE) was successfully developed. • The anodic peak was characterized to be a diffusion-controlled process. • The developed electrode efficiently detected CHZ in both pharmaceutical tablet and a pathological sample, like urine. The electrosensing of chlorzoxazone (CHZ) was studied for the first time at nanostructured Au/graphene modified glassy carbon electrode (AuNPs/Gr/GCE) employing different voltammetric techniques viz. cyclic, linear sweep and differential pulse voltammetries. The results indicated that the voltammetric response of CHZ was improved distinctly at the AuNPs/Gr/GCE electrode than that at bare GCE. In order to carry out the CHZ determination, the dependency of the response current on supporting electrolyte pH, sweep rate and CHZ concentration were inspected to optimize the investigational conditions. The surface characterizations of the Au/graphene modified and unmodified glassy carbon electrodes were carried out. The anodic peak showed a process of diffusion-control. The number of electrons transferred was calculated to be two. The determination of [CHZ] using the modified electrode was studied over the range of 1.0 × 10⁻⁷ M to 10.0 × 10⁻⁷ M which showed the LOD value to be 1.164 × 10⁻⁸ M. The study of excipients showed that the method owns selectivity. A differential pulse voltammetry which is fast and simple, showed a good accuracy and precision, for the purpose of determining the [CHZ] in biomedical applications like pharmaceutical formulation and also in pathological sample testing. In addition, this type of work can find its usage towards scientific purposes that involves electrical measurements, particularly in industrial quality management, environmental pollution management, as it involves simple sample preparation, appreciable repeatability, reproducibility and also high sensitivity.