Abstract

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

Highlights

  • Vitamin B6 (VB6) is a part of water-soluble B complex vitamins and is found in chemically related forms, i.e., pyridoxine (PN), pyridoxal (PL), pyridoxamine (PM), and their phosphorylated derivatives [1]

  • The particle size distributions (PDSs) of zeolite and carbon black (CB) determined by the dynamic light scattering (DLS) method (Fig. 1B) confirm the microsized character of their particles

  • The achieved limit of detection (LOD) value of the developed protocol is more favorable than the results presented in most of the previously reported analytical methods used for VB6 determination

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Summary

Introduction

Vitamin B6 (VB6) is a part of water-soluble B complex vitamins and is found in chemically related forms, i.e., pyridoxine (PN), pyridoxal (PL), pyridoxamine (PM), and their phosphorylated derivatives [1]. In order to improve the analytical performance of a VB6 electrochemical sensor, more and more functional materials have been used to fabricate chemically modified electrodes (CMEs). Two of the most common approaches appearing in the literature are related to the dispersion of zeolite microparticles within conducting carbon-based composite matrices or deposition of a zeolitepolymeric film (with or without carbon) on the solid-electrodes surface [32] In both strategies, the application of graphite as an electron-conducting component of ZMEs has been reported so far [33, 34]. CB provides many advantages in the electrodes surface modification, such as large specific surface area, low density, disordered structure, electrochemical stability, and high electron conductivity, which in association with features of electrochemically attractive materials, like zeolites, can lead to significant improvement of the analytical performance of sensors [35]. The spectra were collected in the range of 200 to 500 nm with the speed of spectrum registration of 200 nm min−1 and 2.0 nm slit width

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