Bare Carbon Paste Research Articles

Total flavonoid content in plant derived beverages determined by extractive stripping voltammetry

The catechin (CAT)-equivalent of flavonoids content of plant derived-beverages (PDBs) was estimated by partial extraction into the bare carbon paste and subsequent determination by differential pulsed voltammetry (DPV). The selectivity of the method was investigated by determining in presence of the potential interferences. While the determination of CAT in the presence of some non-flavonoid interferences was not possible by direct voltammetry, there was no interfering effect observed in the developed method. The effect of various paste compositions was studied on the extraction of the CAT onto the paste, and it was found that the combination of expanded graphite with silicon oil provides the best paste for the extraction. The RSD of 3.93% confirms a good repeatability of the developed method when 5 repetitive measurements were carried out. The LOD and LOQ of the developed method were calculated to be 1.2 × 10−8 M and 3.9 × 10−8 M, respectively. The accuracy of the developed method was controlled by analysis of the spiked sample, where the recovery rate of 98% and 104% indicate the accuracy of the developed ex-situ method. Finally, the developed method was successfully used for the determination of CAT-equivalent of flavonoids in a green tea sample.

A caffeic acid electrochemical sensor amplified with GNR/CoFe2O4@NiO and 1-Ethyl-3-methylimidazolium acetate; a new perspective for food analysis

Determining Caffeic acid is important as an antioxidant compound in food. In this study, caffeic acid (CA) was measured using a carbon paste electrode modified with GNR/CoFe2O4@NiO and 1-Ethyl-3-methylimidazolium acetate (EMIM Ac) as ion liquid. A simple sensor showed a higher current than a bare carbon paste; thus, it can be said that the modified electrode has a higher sensitivity for detecting CA. The linear range of this sensor and its detection limit was equal to 0.01–100.0 μM and 0.01 μM, respectively. Moreover, the developed electrode indicated outstanding selectivity in the presence of several interferences, high sensitivity, reproducibility, and long-term stability. The percentage recovery of CA obtained with the developed sensor affirmed its reliability for CA determination in real samples. The modified sensor's accuracy was confirmed to identify this analyte according to the results.

Voltammetric Determination of Sulfaclozine Sodium at Sephadex-modified Carbon Paste Electrode

The electrochemical behavior of Sulfaclozine Sodium (SLC) was studied at a bare and sephadex-modified carbon paste electrodes by cyclic voltammetry and square wave voltammetry. The cyclic voltammetry (CV) showed a well-defined irreversible oxidation peak at 0.94 V in Britton- Robinson buffer pH 7.0. The strong affinity of SLC to sephadex allowed accumulation of SLC at the surface of electrode and thus higher electrochemical sensitivity to SLC. The influence of sephadex loading, the pH of the solution and the scan rate on the peak current was studied. A linear calibration curve covering the concentration range from 0.005 to 1 mM was obtained using SWV. The method was successfully applied for the determination of SLC in the veterinary pharmaceutical formulations with satisfactory accuracy and precision.

Poly (vanillin) modified carbon paste electrode for the determination of adrenaline: A voltammetric study

The bare carbon paste (BCPE) was modified by electrochemical deposition of vanillin on the surface of carbon paste electrode and applied for the study of electrochemical behavior of Adrenaline (AD) and Uric acid (UA) using cyclic voltammetric and differential pulse voltammetric techniques. Compared to bare carbon paste electrode, a good enhancement in peak current was observed at modified carbon paste electrode. The effect of scan rate and concentration on the oxidation of Adrenaline and uric acid was examined and it was found that the oxidation peak current was proportional to the scan rate and concentration, the LOD and LOQ were found that 5.4 µM and 18 µM. The poly (Vanillin) modified carbon paste electrode showed significantly higher sensitivity and selectivity and used for the simultaneous determination of Adrenaline and uric acid which gives good report.

Role of heat on the development of electrochemical sensors on bare and modified Co 3 O 4 /CuO composite nanopowder carbon paste electrodes

The Co3O4/CuO composite nanopowder (NP) was synthesized by a mechanochemical method and characterized by using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The synthesized Co3O4/CuO NP was used as a modified carbon paste electrode (MCPE) and further the bare carbon paste and Co3O4/CuO NP modified carbon paste was heated at different temperatures (100, 150, 200 and 250 °C) for 10 min. The Co3O4/CuO NP MCPE was used to study the consequences of scan rate and dopamine concentration. Furthermore the preheated modified electrodes were used to study the electrochemical response to dopamine (DA), ascorbic acid (AA) and uric acid (UA).

Enzymatic Biosensor Based on Carbon Paste Electrodes Modified with Gold Nanoparticles and Polyphenol Oxidase

AbstractThe results presented here demonstrate the important catalytic effect of a carbon paste electrode modified by dispersion of gold nanoparticles towards different electroactive compounds. The oxidation of hydrogen peroxide starts at potentials 400 mV less positive than at bare carbon paste, while the reduction, almost negligible at bare carbon paste, starts at 0.100 V. The influence of the size and amount of gold nanoparticles in the composite matrix on the response of the electrode is discussed. The incorporation of albumin within the carbon paste facilitates the dispersion of gold nanoparticles, improving substantially the catalytic effects. At carbon paste modified with gold nanoparticles and albumin, the peak potential separation for hydroquinone decreases from 0.385 V to 0.209 V while the reduction current increases from 16.6 to 75.2 μA. The immobilization of polyphenol oxidase within the carbon paste electrode modified with nanoparticles has allowed us to obtain a very sensitive biosensor for dopamine even in the presence of large excess of ascorbic acid.

Cathodic stripping voltammetric determination of doxazosin in urine and pharmaceutical tablets using carbon paste electrodes.

Several voltammetric techniques were used to explore the reductive behaviour of the antihypertensive agent doxazosin on a bare carbon paste (CPE) and a Tenax-modified carbon paste electrode (TMCPE). The results indicate that the process is irreversible and fundamentally controlled by adsorption, which allows doxazosin to be accumulated at the electrode surface. The cathodic adsorptive stripping (AdS) response was evaluated with respect to pH, accumulation variables and instrumental parameters, using differential-pulse (DPV) and square-wave voltammetry (SWV) as redissolution techniques. In both cases, a voltammetric peak close to 0 V in Britton-Robinson buffer (pH 6.6) was obtained after a preconcentration step at 0.55 V for 3 min (2000 rpm) and a subsequent cathodic scan. When the TMCPE was used, the limits of detection were 4.35 x 10(-11) and 5.18 x 10(-11) M for AdS-DPV and AdS-SWV, respectively. The deposition time (3 min) was improved relative to that obtained by means of CPE (6 min). Under the optimum operational conditions, the doxazosin reduction peak showed a linear response in the range from 6 x 10(-11) to 1 x 10(-9) M by using AdS-DPV, with an RSD of 3.39% for 3 x 10(-8) M doxazosin solution (n = 10). A method was developed for the determination of doxazosin in human urine and formulations.