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This paper describes the development of 1-methyl-3-butylimidazolium chloride ionic liquid/cobalt hexacyanoferrate nanoparticle modified multi-walled carbon nanotubes nanocomposite paste electrode for the electrocatalytic and adsorptive stripping voltammetric and impedimetric determination of diclofenac (DIC) in real samples. The nanocomposite was prepared by a simple chemical method and was characterised by scanning electron microscopy, Fourier transform infrared spectroscopy and atomic absorption spectroscopy. Also, the electrochemical behaviours of the modified electrode and the electrocatalytic oxidation of DIC were investigated in detail by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy techniques. The kinetic parameters such as electron transfer coefficient, and apparent rate constant for the redox reaction between DIC and the modified electrode were also determined using electrochemical approaches. It was found that the modified electrode exhibited excellent electrocatalytic activity toward the oxidation of DIC, and under the optimised conditions, the linear response range and detection limit were found to be 1.0–100.0 and 0.3 μM, respectively using the differential pulse voltammetry method. The proposed method was applied for the sensitive and selective determination of diclofenac in the urine samples and pharmaceutical formulations with satisfactory results. [ABSTRACT FROM AUTHOR]

A carbon paste electrode modified with multiwall carbon nanotubes (MWCNTPE) was prepared to study the electrocatalytic activity of dopamine (DP) in the presence of homocysteine (HCy) and it was used for the determination of HCy. The diffusion coefficient of HCy (D = 6.79x10-6 cm² s-1), and the kinetic parameters of its oxidation, such as electron transfer coefficient (α = 0.46), and rate constant (kh = 7.44x10² dm³ mol-1 s-1) were also determined using electrochemical approaches. Under the optimum pH of 5.0, the peak current of oxidation of HCy at MWCNTPE in the presence of DP occurred at a potential of about 530 mV and the results showed that the oxidation peak current of HCy at the modified carbon nanotubes electrode was higher than on the unmodified electrode. The peak current of differential pulse voltammograms of HCy solutions increased linearly in the range 3.0-600 μM HCy with a detection limit of 2.08 μM HCy. This method was also examined for determination of HCy in physiological serum and urine samples. [ABSTRACT FROM AUTHOR]

We propose chlorpromazine (CHP) as a new mediator for the rapid, sensitive, and highly selective voltammetric determination of homocysteine (Hcy) using multiwall carbon nanotube paste electrode (MWCNTPE). The experimental results showed that the carbon nanotube paste electrode has a highly electrocatalytic activity for the oxidation of Hcy in the presence of CHP as a mediator. Cyclic voltammetry, double potential step chronoamperometry, and square wave voltammetry (SWV) are used to investigate the suitability of CHP at the surface of MWCNTPE as a mediator for the electrocatalytic oxidation of Hcy in aqueous solutions. The kinetic parameters of the system, including electron transfer coefficient, and catalytic rate constant were also determined using the electrochemical approaches. In addition, SWV was used for quantitative analysis. SWV showed wide linear dynamic range (0.1- 210.0 µM Hcy) with a detection limit of 0.08 µM Hcy. Finally, this method was also examined as a selective, simple, and precise electrochemical sensor for the determination of Hcy in real samples. [ABSTRACT FROM AUTHOR]