Electrochemical sensing platform based on Zeolite/Graphite/Dimethylglyoxime nanocomposite for highly selective and ultrasensitive determination of nickel.

In this work, the fabrication and analytical application of a novel, unique, mercury-free, and user-friendly voltammetric sensor of Ni(II) based on glassy carbon electrode (GCE) modified with zeolite(MOR)/graphite(G)/dimethylglyoxime(DMG) composite (MOR/G/DMG-GCE) and the voltammetric procedure for highly selective, ultra-trace determination of nickel ions were reported for the first time. Deposition of a thin layer of the chemically active MOR/G/DMG nanocomposite enables the selective and effective accumulation of Ni(II) ions in the form of the DMG-Ni(II) complex. In 0.1 mol L-1 ammonia buffer (pH 9.0), the MOR/G/DMG-GCE exhibited linear response in the Ni(II) ions concentration range of 0.86 - 19.61 µg L-1 and 0.57 - 15.75 µg L-1, for the accumulation time of 30 s and 60 s, respectively. For 60 s of accumulation time, the limit of detection (S/N = 3) was 0.18 µg L-1 (3.04 nM), and sensitivity of 0.202 µA L µg-1 was achieved. The developed protocol was validated by the analysis of wastewater certified reference materials. Its practical usefulness was confirmed by the determination of nickel released from metallic jewelry submerged in artificial sweat and stainless steel pot during water boiling. The obtained results were verified by electrothermal atomic absorption spectroscopy as a reference method.

Electrochemical Assays for the Determination of Antidiabetic Drugs-A Review.

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.

Electrochemical sensor based on Ni-exchanged natural zeolite/carbon black hybrid nanocomposite for determination of vitamin B6.

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 VB6 with 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-1 was in the range 2.5-5.4% (n = 4). The developed NiZCB-GCE was successfully applied to the determination of VB6 in commercially available multivitamin dietary supplements, food, and water samples. The obtained recoveries ranged from 95 to 106%.

High selective potentiometric sensor for determination of nanomolar con-centration of Cu(II) using a polymeric electrode modified by a graphene/7,7,8,8-tetracyanoquinodimethane nanoparticles.

In this paper we present several possibilities for modification of the all-solid-state copper(II)-selective electrodes in order to obtain high stability and selectivity potentiometric sensor signal. The copper(II)-selective electrodes were modified in a simple way by introducing solid contact layer based on graphene or graphene oxide, 7,7,8,8-tetracyanoquinodimethane or its copper salt. Each of electrodes shown a Nernstian response, wide linear range of Cu2+ concentration and a low detection limit. Nevertheless, some differences between the groups of electrodes have been noticed and resulted from application of intermediate layers of various compositions. The electrode modified with graphene and 7,7,8,8-tetracyanoquinodimethane nanocomposite exhibited the best potential reproducibility and detection limit. Moreover, prepared sensors were characterized by an improved selectivity for copper(II) in relation to non-modified electrodes. The developed electrodes were successfully used for the Cu2+ determination in different samples and results were comparable with those obtained using voltammetry.