Electrochemical study of hydrochlorothiazide on electrochemically pre-treated pencil graphite electrode as a sensor

An electrochemical anodic behavior of hydrochlorothiazide (HCTZ) was studied by using electrochemically pretreated pencil graphite electrode (EPPGE) using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). Two anodic peaks were observed at peak potential 842mV and 1091mV on EPPGE at phosphate buffer (pH7.0). Electrooxidation process of HCTZ shows diffusion-controlled process on EPPGE. DPV and SWV show a good linearity in the concentration range 4μM to 140μM and 1μM to 20μM, respectively. The limits of detection were found to be 3.25μML−1 and 0.421μML−1, respectively. Electrochemical impedance spectra (EIS) gave the charge transfer resistance at EPPGE (32.3kΩ) and PGE (867kΩ), which shows an increase in the electron transfer rate at EPPGE than that of PGE. Surface area, sensitivity and electron transfer kinetic parameters were studied. Electrochemical pretreatment is a simpler method compared to other modifications for the electrodes and this method could be applied for the sensitive determination of HCTZ present in pharmaceutical formulations and urine samples. Keywords: Cyclic voltammetry, Differential pulse voltammetry, Electrochemically pretreated pencil graphite electrode, Square wave voltammetr

An organically modified exfoliated graphite electrode for the voltammetric determination of lead ions in contaminated water samples

This work presents a new electrode, 2-benzoylnaphtho 2,1-b]furan hydrazone exfoliated graphite paste electrode (B-EGPE) fabricated for the differential pulse anodic stripping voltammetric determination of lead (Pb). Under the optimal conditions, Pb2+ could be detected in the concentration range from 2.75 x 10(-7) to 1.5 x 10(-6) mol/L with the linear regression equation, y = 19.41 x 10(-6) x + 0.4249 x 10(-9) with R = 0.99. Interferences from other ions were investigated and the proposed method was further applied to the trace levels of Pb2+ detection in real samples with satisfactory results

Development of multi-walled carbon nanotubes modified pencil graphite electrode for the electrochemical investigation of aceclofenac present in pharmaceutical and biological samples

A sensitive and novel chemically modified multi-walled carbon nanotubes modified pencil graphite electrode (MCPGE) has been developed for the electrochemical investigation of aceclofenac (ACF). MCPGE was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Phosphate buffer solution (PBS) of pH7.0 was used as a suitable electrolytic medium, in which aceclofenac (ACF) exhibited a sensitive adsorption controlled oxidation peaks at +0.12, +0.32 and +0.51V and a reduction peak at −0.26V (vs Ag/AgCl). The experimental conditions were optimised by means of investigating the dependence of peak current on solution pH, concentration and scan rate etc. The electrochemical parameters such as surface concentration (Γ), electron transfer coefficient (α) and the standard rate constant (ks) were investigated at MCPGE. The oxidative peak currents were varied linearly with concentration in the range between 1×10−6 to 60×10−6M with a detection limit of 2.6×10−9M. The UV–Vis absorption spectrum of ACF gave the λmax at 272–273nm and is attributed to the presence of ACF. The applicability of the MCPGE was illustrated by the determination of ACF present in pharmaceutical and human urine samples. Keywords: Aceclofenac, Multi-walled carbon nanotubes, Pencil graphite electrode, Cyclic voltammetry, Differential pulse voltammetr