The utilization of environmentally friendly nanoporous natural zeolite exchanged with Ni²⁺ions (NiZ) and conductive carbon black (CB) in the fabrication of a novel and selective voltammetric sensor of vitamin B₆(VB₆) is presented. The used clinoptilolite-rich zeolite material and CB were characterized in terms of morphology and textural properties. The superior properties of Ni-zeolite/carbon black modified glassy carbon electrode (NiZCB-GCE), arising from the synergistic effect of combining the unique features of zeolite and conductive carbon black, were confirmed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. In the determination of VB₆with the use of differential pulse voltammetry (DPV), the optimization of the pH value of supporting electrolyte and instrumental parameters, as well as the interference study were performed. Under optimized conditions, the oxidation peak current at the potential +0.72 V vs. Ag | AgCl | 3 M KCl reference electrode was linear to the VB₆ concentration in the range 0.050 to 1.0 mg L⁻¹(0.30–5.9 μmol L⁻¹) (R = 0.9993). The calculated limit of detection (LOD,S/N = 3), equal to 15 μg L⁻¹(0.09 μmol L⁻¹), was much better compared to chemically modified electrodes with other carbon-based materials. The RSD for 0.5 mg L⁻¹was in the range 2.5–5.4% (n = 4). The developed NiZCB-GCE was successfully applied to the determination of VB₆in commercially available multivitamin dietary supplements, food, and water samples. The obtained recoveries ranged from 95 to 106%.Graphical abstract

This article presents the current state of knowledge regarding electrochemical methods for determining the active substances within drugs that are used in the treatment of type 1 and type 2 diabetes. Electrochemical methods of analysis, due to their sensitivity and easiness, are a great alternative to other, usually more expensive analytical assays. The determination of active substances mentioned in this review is based on oxidation or reduction processes on the surface of the working electrode. A wide variety of working electrodes, often modified with materials such as nanoparticles or conducting polymers, have been used for the highly sensitive analysis of antidiabetic drugs. The presented assays allow us to determine the compounds of interest in various samples, such as pharmaceutical products or different human bodily fluids.