Voltammetric determination of pyridoxine by use of a carbon paste electrode

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%.

Simultaneous determination of vitamin B12 and its derivatives using some of multivariate calibration 1 (MVC1) techniques

Resolution of binary mixtures of vitamin B12, methylcobalamin and B12 coenzyme with minimum sample pre-treatment and without analyte separation has been successfully achieved by methods of partial least squares algorithm with one dependent variable (PLS1), orthogonal signal correction/partial least squares (OSC/PLS), principal component regression (PCR) and hybrid linear analysis (HLA). Data of analysis were obtained from UV-vis spectra. The UV-vis spectra of the vitamin B12, methylcobalamin and B12 coenzyme were recorded in the same spectral conditions. The method of central composite design was used in the ranges of 10-80 mg L(-1) for vitamin B12 and methylcobalamin and 20-130 mg L(-1) for B12 coenzyme. The models refinement procedure and validation were performed by cross-validation. The minimum root mean square error of prediction (RMSEP) was 2.26 mg L(-1) for vitamin B12 with PLS1, 1.33 mg L(-1) for methylcobalamin with OSC/PLS and 3.24 mg L(-1) for B12 coenzyme with HLA techniques. Figures of merit such as selectivity, sensitivity, analytical sensitivity and LOD were determined for three compounds. The procedure was successfully applied to simultaneous determination of three compounds in synthetic mixtures and in a pharmaceutical formulation.

Voltammetric determination of pyridoxine (Vitamin B6) by use of a chemically-modified glassy carbon electrode

A novel carbon nanotube-modified glassy carbon electrode was described for the direct determination of pyridoxine. The electrochemical behavior of pyridoxine was investigated, and a well-defined oxidation peak with high sensitivity was observed at the modified electrode. Owing to the unique structure and extraordinary properties of multi-wall carbon nanotube (MWNT), the MWNT-modified glassy carbon electrode shows obvious electrocatalytic activity to the oxidation of pyridoxine, since it greatly enhances the oxidation peak current of pyridoxine as well as lowers its oxidation overpotential. Based on this, a very sensitive and simple voltammetric method was developed for the measurement of pyridoxine. A sensitive linear voltammetric response for pyridoxine was obtained in the concentration range of 5 x 10(-7)-1 x 10(-4)mol/L, and the detection limit is 2 x 10(-7)mol/L using differential pulse voltammetry. Compared with other voltammetric methods, this proposed method possesses many advantages such as very low detection limit, fast response, low cost and simplicity. The practical application of this new analytical method was demonstrated with pyridoxine drugs.

Simultaneous determination of melatonin and pyridoxine in tablets by gas chromatography-mass spectrometry

A gas chromatographic-mass spectrometric (GC-MS) method for the qualitative and quantitative determination of melatonin plus pyridoxine commercial tablets is described. Melatonin and pyridoxine were simultaneously determined by GC-MS after extraction from ground tablets with methanol and derivatization with N-methyl-N-N-trimethlylsilyltrifluoroacetamide (MSTFA). The mass chromatograms were generated using 232 m/z ion for melatonin and 280 m/z ion for pyridoxine, respectively. Splitless injection offers good reproducibility with a standard deviation of 2%. The developed method was applied to analyze the melatonin and pyridoxine content from two different tablet formulations. Also, recovery, detection and quantification limits are reported.

The application of differential pulse voltammetry at the glassy carbon electrode to multivitamin analysis

Differential pulse voltammetry at the glassy carbon electrode has been applied to the determination of ascorbic acid, pyridoxine and folic acid in a multivitamin preparation. The individual vitamins all gave well-defined peaks in the anodic region with a linear response of peak current to concentration. The water-soluble vitamins were extracted into aqueous solution and folic acid into dibasic potassium phosphate solution. Before determination of pyridoxine, the ascorbic acid peak was depressed by reaction with formaldehyde. Iron (II) present in the multivitamin preparation did not interfere with the analysis. The voltammetric method compared favourably in terms of accuracy and precision with official methods: it was found to be much simpler, with sample manipulation kept to a minimum. The method was found to be generally applicable to the determination of the vitamins in several multivitamin preparations, or, in simplified form, to the determination of the individual vitamin preparations.