Analytical & Bioanalytical Electrochemistry
Volume:6 Issue: 4, Aug 2014

Battery graphite rod was modified with Ni nanoparticles with a new electroless procedure and the performance of the proposed electrode was evaluated as a non-enzymatic anode for electrocatalytic oxidation of glucose in alkaline media. Glucose fuel cells that useenzymes or microorganisms catalysts are limited by their extremely low power output andrather short durability. The structure and morphology of the electrode surface were examined with X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM) techniques. Voltammetric and amperometric studies indicated that the onset potential of the glucose oxidation is low (~ 0.3 V) and the electrode stability is good. In addition to these advantageous, due to easily preparation and low cost, it will be used probably in glucose fuel cells as an anode.

Selective poly (vinylchloride) membrane electrodes based on a quaternary ammonium compound, malachite green as a novel ion exchanger for anionic species were prepared. The developed membrane electrodes were used successfully for the quantification of sulphadimethoxine, iodide ions and thiocyante ions in their pure powdered forms, fishwater and/or pharmaceutical formulation. Linear responses were obtained within a concentration range of 10-5-10-2 M for the three selected monovalent anionic species. The electrodes exhibited unusual half Nernstian slopes when the divalent cationic malachite green is used as a novel lipophilic ion exchanger in PVC based membranes for determination of monovalent anions. They have fast response times about 20 s, satisfactory reproducibility, and long life times.

The ethyl cellulose manganese(II) hydrogen phosphate was synthesised by sol-gel method using various 1:1 electrolytes at different temperature and concentration. Thesematerials were characterized by using Fourier transform infrared (FTIR) spectroscopy, Ultraviolet-visible (UV-vis) spectroscopy and pH meter. This material refers a new class of material as it contains both organic that is a polymer and inorganic parts along with the improved chemical as well as mechanical stabilities. The material conductivity generally decreases in the order K+>Na+ for 1:1 electrolyte solution. This study displayed the applications of conductivity of materials in the varied field of science. The material exhibited inhibitory results against gram positive bacteria like Staphylococcus aureus (MSSA-22) and gram negative bacteria like Escherichia coli (K-12), and it marked the enhancement in the effectiveness of the antibacterial agent.

In this research, we reported a novel modified carbon ceramic electrode using CuI as modifier was fabricated by sol-gel technique. The electrocatalytic activity of the copper iodide modified sol-gel derived carbon ceramic (CIM-SGD-CC) electrode was examined for the oxidation of ascorbic acid (AA). Results showed that the CIM-SGD-CC electrode has high catalytic ability for electrooxidation of ascorbic acid. The response current exhibited good linear relationship for the concentration of ascorbic acid in the range from 5×10-4 to 5×10-3 mol L-1, with the correlation coefficient of 0.9902 and the detection limit of 1.66 μmol L–1. The kinetic parameter such as the electron transfer coefficient (α) and exchange current density (j0) for the modified electrode were calculated. The advantages of the modified CCE are its good stability and reproducibility of surface renewal by simple polishing, excellent catalytic activity and simplicity of preparation.

A screen printed carbon electrode (SPCE) containing the electrocatalyst Meldola’s Blue (MB) has been investigated as the base transducer for a glutamate biosensor. The sandwich biosensor was fabricated by firstly depositing a chitosan (CHIT) layer onto the surface of the transducer (MB-SPCE), followed by glutamate dehydrogenase (GLDH): thisdevice is designated GLDH-CHIT-MB-SPCE. NAD+ was added to buffer solutions prior to the measurement of glutamate. This biosensor was used in conjunction with amperometry in stirred solution at an applied potential of +0.1 V (vs. Ag/AgCl). Optimum conditions for the analysis of glutamate were found to be as follows: temperature, 35 °C; buffer, pH 7; ionic strength, 75 mM; NAD+, 4 mM; CHIT 0.05% in 0.05 M HCl; GLDH, 30 U. The linear range of the biosensor was found to be 12.5 μM to 150 μM, the calculated limit of detection (based on three times signal to noise) was 1.5 μM and the sensitivity was 0.44 nA/μM. The proposed biosensor was used to measure glutamate in serum before and after fortification with glutamate. The endogenous concentration of glutamate was found to be 1.68 mM and the coefficient of variation (CV) was 4.1%. The serum was then fortified with 2 mM of glutamate, and the resulting mean recovery was 96% with a CV of 3.3% (n=6). An unfiltered beef OXO cube was analysed for monosodium glutamate (MSG) content. The endogenous content of MSG was 125.43 mg/g with a CV of 8.98%. The OXO cube solution was fortified with 0.935 g (100 mM) of glutamate, the resulting mean recovery was 91% with a CV of 6.39%.

Hydrolysis of paracetamol in acidic media was studied using electrochemical technique in different reaction temperatures. Based on the fact that both paracetamol (PAR) and its hydrolyzed product, p-aminophenol (PAP) are both electroactive and their voltammetric peaks do not overlap, differential pulse voltammetry was used for the determination of the remained PAR concentration in the reaction vessel as well as produced PAP concentration. Then, the kinetic parameters of PAR hydrolysis including reaction rates and half-lives in various temperatures and the activation energy of the reaction were calculated using proposed accurate method. PAR is hydrolyzed to PAP in the presence ofhydronium ion via first-order kinetic reaction with the reaction rates of 8.9×10-4, 2.16×10-3, 4.21×10-3, 6.26×10-3 and 1.46×10-2 min-1 at the reaction temperatures of 50, 60, 70, 80 and 90 °C, respectively. The activation energy of the hydrolysis reaction was calculated to be 63.61 kJ mol-1.

Three novel moxifloxacin (MO) selective electrodes were investigated with 2-nitrophenyl octyl ether as a plasticizer in a polymeric matrix of polyvinyl chloride (PVC). Sensor 1 was fabricated using tetrakis(4-chlorophenyl)borate (TpClPB) as an anionic exchanger without incorporation of an ionophore. Sensor 2 used 2- hydroxyl β-cyclodextrin as an ionophore while sensor 3 was constructed using 4-tertary butyl sulfocalix-8-arene as an ionophore. Linear responses of MO within the concentration ranges of 10−5 to 10−2 mol L−1 were obtained using sensors 1, 2 and 3, respectively. Near Nernstian slopes of 49.79, 51.50and 52.10 mV/decade over the pH range of 2–5 were observed. The selectivity coefficients of the developed sensors indicated excellent selectivity for MO. The proposed sensors displayed useful analytical characteristics for the determination of MO in bulk powder, pharmaceutical formulation, and biological fluids (plasma) and in the presence of its alkaline degradation product and thus could be used for stability-indicating studies.

Precisely detection of specific ion in a solution with ion electrodes provides valuable clinical and chemical information. For this purpose, specific ion selective electrodes have been designed, which are able to detect the concentrations of specific ions as much as 10-5 M. In this study, we introduced a polyvinylchloride (PVC)–based membrane of Dibenzo-18-crown-6 (DB18C6), which exhibited good potentiometric response for K+ over a wideconcentration range of 1.0×10-5 to 1.0×10-2 mol L-1. The best Nernstian slope for the desired electrode was 53 mV/decade of K+ concentration. Matched potential method (MPM) was used for determination of selectivity coefficient. The response time for the K+ selective electrode was 30 s. The electrode was used for a period of 4 weeks. Our results showed that the electrode can be used in wide pH range from 3.0 to 9.5. Electrode was successfully applied for determination of potassium in oral rehydration salts (ORS) and mineral water.

This paper deals with the development of an electrochemical sensor base on Trypan Blue (TB) towards the determination of Dopamine (DA). An electrochemical sensor was fabricated by the electropolymerization of TB onto the Carbon paste electrode (CPE)using cyclic voltammetry (CV) technique. The polymerized TB modified CPE (Poly(TB)MCPE) was characterized using Electrochemical impedance spectroscopy (EIS) and CV techniques. The sensor Poly(TB)MCPE showed good sensitivity and catalytic activity in comparison with bare CPE. Electrochemical behaviour of Dopamine (DA) was investigated in 0.1 M PBS in alkaline medium (pH 8.0) using Poly(TB)MCPE. Moreover, simultaneous determination of DA in presence of Ascorbic acid (AA) and Uric acid (UA) was examined using Differential pulse voltammetry (DPV) technique. Several kinetic parameters such as diffusion coefficient (D0), area of the electrode (A), surface concentration of modifier on Poly(TB)MCPE (Γ), limit of detection (LOD) and limit of quantification (LOQ) were calculated.

A chemically modified carbon paste electrode (MCPE) with tetrachloro-orthobenzoquinone(TOB) was employed to study the electrocatalytic oxidation of sulfite in aqueous solution using cyclic voltammetry (CV) and double-potential step chronoamperometry. It has been found that under an optimum condition (pH 2.0), the oxidation of sulfite at the surface of MCPE occurs at a potential of about 700 mV less positive than that of an unmodified CPE. The diffusion coefficient (D) for sulfite was found as 8.2×10-6 cm2 s-1 by chronoamperometry. The electron transfer coefficient, a, was estimated to be 0.4 and 0.24 for the oxidation of sulfite at the surface of MCPE and unmodified CPE, respectively. The electrocatalytic oxidation peak currents showed a linear dependence on the sulfite concentration in the range of 1×10-4 M -4.2×10-3 M with detection limit (3s) 5.7×10-5 M by CV. This method was also used for selective determination of sulfite in weak liquor.