A voltammetric sensor has been developed based on glassy carbon electrode (GCE) modification with nanocomposite consisting of manganese-based metal-organic framework (JUK-2), multi-walled carbon nanotubes (MWCNTs), and gold nanoparticles (AuNPs) for detection of citalopram (CIT). The composition and morphology of JUK-2-MWCNTs-AuNPs/GCE were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), energy dispersion spectroscopy (EDS), and scanning electron microscopy (SEM). The electrochemical properties investigated using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) indicated that the fabricated hybrid material exhibits the properties of mixed ion-electron conductor (MIEC). Using staircase voltammetry (SCV), under optimized conditions, the fabricated sensor shows a linear response in three CIT concentration ranges, 0.05–1.0, 1.0–10.0 and 15.0–115.0 μmol L−1, with a detection limit of 0.011 μmol L−1. The JUK-2-MWCNTs-AuNPs/GCE was successfully employed for the determination of CIT in pharmaceutical, environmental waters, and biological samples with satisfactory recoveries (98.6–104.8%). Graphical abstract

Voltammetric sensors with laterally placed working electrode are an interesting alternative to classic electrodes since they offer enhanced performance in electroanalysis. Their characteristics include easier preparation for measurement, removal of interferences and gas bubbles, amplification of mass-transport, and possibility of miniaturization and automation. In this review, construction and characteristics of the custom-designed in our team cyclically renewable, silver, gold, bismuth, glassy carbon, ceramic and amalgam annular band, bi-band, ring, and multidisc electrodes are discussed in detail. They represent the current trends in electroanalysis, aimed at reducing of amount of the used toxic electrode materials, like mercury and its compounds, and organic solvents used for a sample preparation, and are coherent with the concept of Green Chemistry. For each sensor type available strategies for mechanical and electrochemical surface renovation/activation before measurement are elucidated and evaluated on the basis of interpretation of voltammetric and tensammetric curves. Particular attention is put on electrochemical characteristics of the described sensors and their application for determination of trace amounts of metal ions and their complexes, organic compounds, and surface-active substances by means of tensammetry, and anodic, cathodic, adsorptive and catalytic adsorptive stripping voltammetry. Final considerations are addressed to the possibility of measurement automation and related future prospects.

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In this work, low‐cost and environmentally friendly natural zeolite exchanged with Mn2+ cations was used for the first time to modify the glassy carbon electrode with the aim to obtain a fast and simple sensor for voltammetric determination of paracetamol (PAR). The Mn‐zeolite/graphite modified glassy carbon electrode (MnZG−GCE) was prepared by evaporation of solvent from dispersion of the zeolite/graphite mixture with the polymer in acetone. The electrochemical characteristics of MnZG−GCE were conducted by electrochemical impedance spectroscopy and cyclic voltammetry. Compared with graphite modified GCE (G−GCE), MnZG−GCE exhibited better electrochemical parameters, which confirms the superiority of applying zeolite in the proposed sensor. The optimization of the pH‐value of supporting electrolyte and instrumental parameters were carried out. The peak current was proportional to the concentration of PAR in a phosphate buffer saline of pH 6.0 in the range from 0.029 to 0.69 mg L−1 (R=0.9997) with limit of detection of 8.8 μg L−1. Finally, the proposed electrode was successfully applied to determine the paracetamol in pharmaceutical formulation and certified reference materials. The satisfactory recoveries, which ranged from 89.2 to 102.7 %, were obtained for all studied samples. It confirmed the attractiveness of relatively inexpensive, easy to fabricate and non‐toxic MnZG−GCE in determination of PAR in complicated matrixes.

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%. Graphical abstract

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