mohamed abdel sabour

Reduced graphene oxide was estimated for the modification of a glassy carbon electrode. The fabricated electrode was employed for folic acid determination in 0.1 M KCl solution (pH 14) using cyclic, linear sweep, differential pulse voltammetric and chronoamperometric techniques. The modified sensor exhibits a high electro-catalytic activity towards FA oxidation in the presence of ascorbic acid. The anodic peak current (IP) of FA increased linearly with an increase in pH (12.6–14) and scan rate (20–500 mV/s) at the ERGO/GCE. Good linearity was obtained between IP and FA concentrations (3.01–7.23 µM) with the detection (LOD) and quantification (LOQ) limits are 4.68 and 15.6 nM, respectively. Under diffusion control, the diffusion coefficient was estimated to be 2.88×10−6 cm2/s at the ERGO/GCE. The fabricated sensor gives high selectivity, good sensitivity and excellent reproducibility. Thus, the proposed method could be applied to detect FA in pharmaceutical formulations and urine samples.

A selective and sensitive voltammetric sensor was constructed using a Poly(methyl orange)/glassy carbon electrode (PMO/GCE). The PMO/GCE sensor was applied to investigate the electrochemical behavior of ascorbic acid (AA) and vitamin B2 (VB2) in PBS buffer solution. The sensor was applied for individual and simultaneous determination of AA and VB2using cyclic and differential pulse voltammetry (DPV) techniques. Different experimental parameters including scan rate(25-500 mV/s), pH (4-8 for AA and 3-10 for VB2) and analyte concentration (10-40 µM for AA and 4-85 µM for VB2) have been studied and optimized. High electrocatalytic activities for AA and VB2 oxidation were achieved at pH 7.0 and 6.0, respectively. In addition, results denoted that the oxidation process of AA and VB2 was under diffusion control. The respective detection limits, quantitation limits and linear ranges were 0.575, 1.916 and 10-40 μM for AA and 0.922, 3.073 and 5-85 μM for VB2under the optimized DPV conditions. Peak separation of AA from VB2was 660 mV which is enough to determine these vitamins simultaneously. The fabricated sensor has been applied successfully for estimation of AA and VB2 in real samples with good selectivity, stability and reproducibility.

The development of a new modified glassy carbon electrode with ZnO nanoparticales and a polymer film of 1, 2-napthaquinone-4-sulphonic acid have been reported. The electrochemical behaviour of paracetamol in pharmaceutical form at ZnONPsNq/GC modified electrode using cyclic and linear sweep voltammetry was investigated. The modified electrode exhibited excellent electrocatalytic activity for the behaviour of PA. The anodic and cathodic peak currents of PA at ZnONPs-Nq/GCME increased significantly when compared with that at a bare glassy carbon electrode and ZnONPs/GCE, also its potential shifted to more negative value. The effect of pH, concentration and scan rate were also investigated. The anodic peak current was linearly proportional to the concentration of PA in the range from 0.088 to 1.1 mM with detection and quantification limits of 30.03×10-6 and 10.01×10-5 M respectively. The pH 7.6 is the gives value for studying the behaviour of PA at the modified electrode. Some parameters such as the diffusion coefficient (D), the electron transfer rate constant (ks) and the electron transfer coefficient (α) were calculated and found for the PA oxidation to be 5.998×10-6 cm2 s–1, 11.279 s-1 and 0.721 respectively. The modified electrode shows high selectivity, satisfied stability and good reproducibility for the detection of PA. This modified electrode was successfully applied to PA determination in pharmaceuticals tablets samples.