Analytical & Bioanalytical Electrochemistry
Volume:3 Issue: 1, Feb 2011

The electrocatalytic oxidation of formaldehyde and acetaldehyde on copper chloride modified copper electrode in alkaline solution was investigated. The process of oxidation and the kinetics have been investigated using cyclic voltammetry, chronoamperometry, and steady-state polarization measurements. The results show that the (ClCu)2O film on the electrode behaves as an efficient catalyst for the electrooxidation of two species in alkaline medium. The CV changes observed indicate that the modifide electrode has a good catalytic activity for the oxidation of formaldehyde and acetaldehyde. The transfer coefficient (α), the number of electrons involved in the rate-determining step (nα) and the catalytic rate constant (k) for modified electrode were calculated.

A novel amperometric hydrogen peroxide biosensor was fabricated for the determination of H2O2. Catalase (Cat) was immobilized on a glassy carbon electrode by poly(glycidyl methacrylate-co-vinylferrocene) (poly(GMA-co-VFc)). A polymeric electron transfer mediator, containing copolymers of glycidyl methacrylate (GMA) and vinylferrocene (VFc) with different molar ratios, have been prepared by free radical copolymerization. Amperometric response was measured as a function of concentration of H2O2, at fixed potential of +0.35 V vs. Ag/AgCl in a phosphate buffered saline (pH 7.5). The mediated hydrogen peroxide biosensor had a fast response of less than 7 s with linear range 0.5-14 mM. The sensitivity of the biosensor for H2O2 was 34 nA/mM.cm2.

A rapid and simple method for the real time monitoring of Brucella abortus CSP-31 (B. abortus CSP-31) by using Surface Plasmon resonance (SPR) is first time reported. SPR and electrochemical impedance spectroscopy (EIS) were used to characterize the B. abortus CSP-31 interaction on carboxymethyldextran modified gold disc with antibody. The EIS data revealed a decrease in impedance after interaction of antigen with antibody due to the effective binding. The present SPR biosensor is able to detect 0.05 pM concentration of B. abortus CSP-31 in phosphate buffered saline in less than 10 minute with linearity from 2.0 to 16.0 pM. The equilibrium constant (KD) and maximum binding capacity of analyte (Bmax) values for B. abortus CSP-31 were calculated to be 7.6 pM and 235.94 m, respectively. This KD value classifies the antibody as a high affinity one towards the antigen. Moreover, thermodynamic parameter change in Gibb’s free energy was calculated and found to be -63.34 kJ/mol. Interference study was also performed with B. abortus cell envelope (CE) antigen and a negative angle change was observed with exemplifying specificity for the antigen-antibody interaction of B. abortus CSP-31.

This study describes the preparation and application of a poly (3,4- ethylenedioxythiophene) (PEDOT) modified glassy carbon electrode for paracetamol determination in pharmaceutical samples. The PEDOT modified electrode was prepared by electropolymerizing 3,4-ethylenedioxythiophene (EDOT) on a glassy carbon electrode in a non-aqueous medium. The best performance of the PEDOT modified electrode in 0. mol L-1 phosphate buffer obtained at pH 7.0. Under these conditions, an oxidation potential of paracetamol was observed at 0.37 V versus Ag/AgCl/sat’d KCl. The cyclic voltammetric study indicates that the PEDOT modified electrode shows a very good electrocatalytic activity by reducing the overpotential by 200 mV for paracetamol oxidation. The modified electrode showed a linear response range between 2.5 and 150 μmol L-1, a sensitivity of 90.03 A/mmol L-1, quantification and detection limits of 2.5 μmol L-1 and 1.13 μmol L-1, respectively. Finally, the proposed method was applied for paracetamol determination in commercial tablets with a mean recovery of (1016) %.

A simple, precise, rapid and low-cost potentiometric method for the determination of pentachlorophenol is proposed. A new pentachlorophenol-sensitive electrode was constructed by incorporating the pentachlorophenol ion pair complex with rhodamine 6G into graphite matrix. The electrode exhibited a linear response over the concentration range of 1×10–5–5×10–2 mol/L, a detection limit of 1.7×10–6 (5.2×10 5) mol/L with a Nernstian slope of 41±1 (68±1) mV/decade. The working pH range is 7.5–10.5. The electrode is easily constructed, has fast response time (3–10 s) and can be used for the period of six months without any considerable deterioration. The proposed sensor displays good sensitivity for pentachlorophenol.

A carbon paste electrode (CPE) modified by multiwalled carbon nanotubes (MWCNTs) and banana tissue was used for detection of dopamine (DA). The modified electrode show good selectivity toward DA in the presence of ascorbic acid (AA). The electrochemical determination of DA at the surface of modified electrode was investigated by differential pulse voltammetry (DPV). The linear curve was obtained in the range of 10-3 μM. The detection limit (3σ) was 2.09 μM for DA. Also the stability of modified electrode was investigated after 20 days, and results show that the modified has relatively good stability.

The title terpolymer (p-COF-II) synthesized by the condensation of p-Cresol (p-C) and Oxamide (O) with Formaldehyde (F) in the presence of acid catalyst and using 2:1:3 molar proportions of the reacting monomers. The synthesized terpolymer resin then characterized by elemental analysis and spectral studies like IR, 1H NMR, 13C NMR and XRD. The morphology of synthesized terpolymer was studied by scanning electron microscopy (SEM).The electrical property was measured over a wide range of temperature (313-403K).The plot of log  vs. 103/T of the resin is linear over a wide range of temperature showing its semiconducting nature. The chelating ion-exchange study was carried out over a wide pH range, shaking time and in media of various ionic strengths for seven metal ions Fe (III), Cu (II), Ni (II), Co (II), Zn (II), Cd (II) and Pb (II) in the form of their metal nitrate solutions. The terpolymer showed a higher selectivity for Fe (III), Cu (II), and Ni (II) ions. Thermal study of the resin was carried out to determine its mode of decomposition and thermal stability. By using data of thermogravimetry various kinetic parameter like frequency factor (Z), entropy change (S), free energy change (F) and apparent entropy (S*) have been determined using Freeman-Carroll method.

A carbon paste electrode was modified with β-cyclodextrin to form a selective electrochemical sensor for determination of Piroxicam (PX). A novel sensitive technique which called fast Fourier transform cyclic voltammetry (FFT CV) was used for measurements of redox current of the component. To have a more defined and intense peak current for piroxicam determination, Tris-HCl buffer (pH=8.0; 0.05 mol L-1) was used as supporting electrolyte. In this aqueous media, PX has been selectively accumulated on the surface of electrode by CD as a modifier. The drug presented one irreversible oxidation peaks at about 500 mV on modified carbon paste electrode vs. Ag/AgCl which produced a higher current. This property was used for analytical purposes by developing a stripping FFTCV method to determine piroxicam. Furthermore, signal-to-noise ratio has significantly increased by application of discrete fast Fourier Transform (FFT) method, background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window. The effective parameters were optimized. As a result, CDL of 5.0×10-9 mol L-1 and LOQ of 8.0×10-9 mol L-1 were obtained. The electrode applied for determination of PX in urine and plasma and formulation samples. The recovery for spiked assay in urine and plasma samples was obtained 101-105% respectively and a good quantification of piroxicam was achieved in a commercial formulation. The effect of some interfering substances was investigated and electrode showed a good selectivity to piroxicam.