Voltammetric behavior of dopamine at a glassy carbon electrode modified with NiFe(2)O(4) magnetic nanoparticles decorated with multiwall carbon nanotubes.

Voltammetric behavior of dopamine was studied on a glassy carbon electrode (GCE) modified-NiFe(2)O(4) magnetic nanoparticles decorated with multiwall carbon nanotubes. Impedance spectroscopy and cyclic voltammetry were used to characterize the behavior of dopamine at the surface of modified-GCE. The modified electrode showed a synergic effect toward the oxidation of dopamine. The oxidation peak current is increased linearly with the dopamine concentration (at pH7.0) in wide dynamic ranges of 0.05-6.0 and 6.0-100μmolL(-1) with a detection limit of 0.02μmolL(-1), using differential pulse voltammetry. The selectivity of the method was studied and the results showed that the modified electrode is free from interference of organic compounds especially ascorbic acid, uric acid, cysteine and urea. Its applicability in the determination of dopamine in pharmaceutical, urine samples and human blood serum was also evaluated. The proposed electrochemical sensor has appropriate properties such as high selectivity, low detection limit and wide linear dynamic range when compared with that of the previous reported papers for dopamine detection.

Ensafi AA ，Arashpour B ，Rezaei B ，Allafchian AR ... -  《-》

Highly selective differential pulse voltammetric determination of phenazopyridine using MgCr2O4 nanoparticles decorated MWCNTs-modified glassy carbon electrode.

A selective modified glassy carbon electrode based on multiwall carbon nanotubes decorated with MgCr2O4 nanoparticles was fabricated and used for the determination of phenazopyridine using differential pulse voltammetry. The electrochemical response of the modified electrode toward phenazopyridine was characterized by different electrochemical methods including differential pulse voltammetry (DPV), cyclic voltammetry (CV), and impedance spectroscopy. The prepared electrode showed an efficient synergic effect on the oxidation of phenazopyridine at pH 6.0. The oxidation peak current was proportional to the concentration of phenazopyridine from 0.05 to 7.5 μmol L(-1). The detection limit was 0.025 μmol L(-1). The applicability of the method was confirmed with satisfactory results obtained through the assay of phenazopyridine in human plasma, urine samples, and pharmaceuticals.

Ensafi AA ，Arashpour B ，Rezaei B ，Allafchian AR ... -  《-》

Multiwall carbon nanotubes decorated with NiFe2O4 magnetic nanoparticles, a new catalyst for voltammetric determination of cefixime.

Multiwall carbon nanotubes were decorated with synthesized NiFe(2)O(4) magnetic nanoparticles. The new materials were characterized with different techniques such as transform infrared spectroscopy, transmission electron microscopy, atomic force microscopy and electrochemical impedance spectroscopy. The multiwall carbon nanotubes decorated with NiFe(2)O(4) magnetic nanoparticles was used as a new mediator for the voltammetric determination of cefixime. Under the optimum conditions at pH 8.0, the oxidation of cefixime was occurred at 850 mV at the surface of the modified electrode. Linear sweep voltammetry exhibited two wide linear dynamic ranges of 0.1-100 and 100-600 μmol L(-1) cefixime. The detection limit was found to be 0.02 μmol L(-1) cefixime. Finally, the modified electrode showed good sensitivity, selectivity and stability for the determination of cefixime in real samples.

Ensafi AA ，Allafchian AR 《-》

Electrocatalytic detection of dopamine in the presence of ascorbic acid and uric acid using single-walled carbon nanotubes modified electrode.

Single-walled carbon nanotubes (SWCNTs) fabricated by sodium dodecyl sulfate (SDS) (f-SWCNTs) modified glassy carbon electrodes (f-SWCNTs/GCE) for the simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). The f-SWCNTs/GCE displayed very good electrochemical catalytic activities with respect to GCE. The oxidation over-potentials of DA and UA decreased dramatically, and their oxidation peak currents increased significantly at f-SWCNTs/GCE compared to those obtained at the bare GCE. Simultaneously, the oxidation peak currents of AA decreased accordingly. The f-SWCNTs/GCE not only divide the overlapping voltammetric responses of them into individual voltammetric peaks, but also totally eliminate the interference from AA and distinguish DA from UA. The catalytic peak currents obtained from square-wave voltammetry increased linearly with increasing DA concentrations in the range of 5.0×10(-6) to 1.0×10(-4)M with a detection limit of 2.0×10(-8)M (S/N=3). The method was also successfully applied for determination of DA and showed good recovery in some biological fluids.

Li Y ，Du J ，Yang J ，Liu D ，Lu X ... -  《-》

Adsorptive anodic stripping differential pulse voltammetric determination of CellCept at Fe(3)O(4) nanoparticles decorated multi-walled carbon nanotubes modified glassy carbon electrode.

A simple and sensitive method based on adsorptive anodic stripping differential pulse voltammetry (AASDPV) for the determination of cellcept, using a magnetic Fe3O4 nanoparticles and functionalized (carboxylated) multi-walled carbon nanotubes modified glassy carbon electrode (f-MWCNs/Fe3O4/GCE) was developed. In phosphate buffer solution (pH = 5), the voltammogram of cellcept exhibited tow anodic peaks and the well-defined peak at about 0.611 V vs SCE was used for its monitoring. The modified electrode was characterized by different methods such as electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and cyclic voltammetry (CV). The experimental parameters, such as pH, deposition potential and time, as well as scan rate were optimized. Under the optimized conditions, Ip (μA) was proportional to the cellcept concentration in the range of 0.05-200 μM (R2 = 0.9989) with a detection limit of 9.0 nM and limit of quantification of 30.2 nM. The recovery was >98%. The practical analytical utilities of the modified electrode were demonstrated by the determination of cellcept in human urine and blood serum samples. Modified electrode showed an adequate sensitivity and stability for evaluated samples.

Gholivand MB ，Solgi M 《-》