Response Of Carbon Paste Electrode Research Articles

Fabrication of an electrochemical sensor based on eggshell waste recycling for the voltammetric simultaneous detection of the antibiotics ofloxacin and ciprofloxacin

In this work, an accurate, highly sensitive, and economical electrochemical sensor based on a carbon paste electrode modified by Ca2CuO3 nanostructure (Ca2CuO3 NS) was constructed using Eggshell waste recycling as a cheap source of calcium. The Ca2CuO3 NS was analyzed using FTIR, SEM, and XRD measurements. The synthesized nanomaterials utilized for the first time to enhance the electrocatalytic efficiency of carbon paste electrode (CPE) toward fluoroquinolones antibiotics ofloxacin (OFL) and ciprofloxacin (CIP), The drugs used to treat pneumonia caused by COVID-19. The synthesized Ca2CuO3 NS dramatically enhanced the anodic peak response of CPE toward both drugs compared to the unmodified one and other modified electrodes. The simultaneous detection of the two antibiotics was performed in the linear range of 0.09–1.0 μM for OFL and 0.05–0.8 μM for CIP with the LOD of 0.027 μM and 0.012 μM, respectively. The suggested method was applied successfully to determine OFL and CIP in real samples.

Electrochemical response of carbon paste electrodes modified with carbon nanotubes: Effects of temperature of nitrogen doping and oxygen functionalization

Carbon paste electrodes (CPE) were modified with nitrogen-doped carbon nanotubes (N-CNTs) synthesized at 750 °C (N-CNT750) and 850 °C (N-CNT850), carboxyl functionalized carbon nanotubes (MWCNTCOOH), and pristine carbon nanotubes (MWCNT). Their electrochemical properties were investigated and compared towards a common redox probe, potassium ferricyanide (K3[Fe(CN)6]). The electrochemical responses were probed using cyclic voltammetry, and the results unveiled that modification with carbon nanotubes enhanced anodic peak currents (Ipa) for the electrodes CPE/MWCNTCOOH, CPE/N-CNT750 and CPE/N-CNT850 (Ipa, p < 0.05 in relation to pure CPE). In particular, CPE modified with N-CNTs synthesized at 850 °C (CPE/N-CNT850) exhibited better electrochemical response, with lower peak-to-peak potential separation (ΔEp, p < 0.05 in relation to pure CPE). Complementary studies were conducted to investigate the electroactive area (A) and heterogeneous electron-transfer kinetics (k0). CPE/N-CNT850 (0.034 ± 0.005 cm2) and CPE/MWCNTCOOH (0.057 ± 0.002 cm2) presented more satisfactory results for the anodic and cathodic electroactive area (A), respectively. Kinetic studies revealed a higher k0 (1.03 × 10−3 cm.s−1) for the CPE/N-CNT850 electrode. Differential pulse voltammetry was employed for the electrochemical detection of Acetaminophen (AC). The response was linear for an AC concentration range from 66.2 to 259.7 μmol L−1, with the lowest detection limit (LOD) of 0.37 μmol L−1 and the highest sensitivity of 0.244 ± 0.002 μA L μmol−1 for the respective electrodes CPE/N-CNT850 and CPE/MWCNTCOOH. The CPE/N-CNT850 and CPE/MWCNTCOOH electrodes show the best correlation of results, the presence of polar groups on the surface of MWCNTCOOH and a higher amount of graphitic nitrogen bond of N-CNT850 suggest that these CNTs are particularly promising for applications in electrochemical fields.

VOLTAMMETRIC DETERMINATION OF ESTRADIOL IN MILK AND PHARMACEUTICALS BASED ON FUMED-SILICA MODIFIED CARBON PASTE ELECTRODE

In this study, modification of carbon paste electrode (CPE) with a nano-structured substance, fumed silica (FS), was investigated to develop a voltammetric method for the determination of an endocrine disrupting chemical, estradiol (EST). FS prominently increased the voltammetric response of CPE towards EST. The parameters that affect the volmametric performance of modified CPE were examined to find the optimal conditions. Modified electrode showed a linear response towards EST between the concentration values of 0.1 mM and 15.0 mM EST. Limit of detection value for the method developed was calculated as 0.023 mM. Production reproducibility of the modified electrode was obtained as 3.6 %. The voltammetric behavior of EST was also examined in the presence of different possible substances to evaluate their interference effects. The modified electrode successfully discriminated the oxidation potential of EST in the presence of different substances. The determination of EST was tested in milk and pharmaceutical samples to evaluate the analytical performance of the method. The recovery analysis of EST in milk samples showed that the modified electrode can be used safely in these samples. The modified electrode also achieved the determination of EST in pharmaceutical samples.

Effect of the substituent of the cation of N-octylpyridinium hexafluorophosphate in the electrical and electrochemical response of carbon paste electrodes modified with these ionic liquids

A series of N-octylpyridinium hexafluorophosphate ionic liquids (ILs), ascribed as ROpyPF6, where Opy = N-octylpyridinium and R are the substituents OCH3, CH3, CF3 and CN at the para position of the cation, were characterized and employed as binders in carbon paste electrodes (CILEs) to evaluate the electron donating or withdrawing effects of the substituent of the cation in physical and electrochemical properties of these CILEs. Substituents strongly affect the melting point of the ILs, the electric properties of the CILEs measured by electrochemical impedance spectroscopy, and the electrochemical behavior measured by the response for an outer-sphere reaction (ferro/ferricyanide redox couple) and for an inner-sphere irreversible reaction (oxidation of sulfite). Results show that ILs can be separated in two different groups: those that have withdrawing electron substituents and those that have donating-electron substituents. OpyPF6 has a behavior similar to those that have withdrawing electron substituents. Carbon paste electrode prepared with mineral oil as binder (CPE) has a very different behavior and is described for comparison purposes only. Results show that the ILs with withdrawing electron substituents have more polarized cations (a more localized positive charge) acquiring a slight ionic character in comparison to the ILs with donating substituents. The electron withdrawing effect modifies the hydrogen-fluorine interactions and also the electrostatic interactions between anion and cation, modifying the electric and electrochemical response of the CILEs, resulting in more conductive and homogeneous surfaces.

Electrochemical response of carbon paste electrode modified with mixture of titanium dioxide/zirconium dioxide in the detection of heavy metals: Lead and cadmium

A novel carbon modified electrode was developed by incorporating titanium dioxide/zirconium dioxide into the graphite carbon paste electrode to detect heavy metals—cadmium and lead. In this work, the development of the novel titanium dioxide/zirconium dioxide modified carbon paste electrode was studied to determine the optimum synthesis conditions related to the temperature, heating duration, amount and ratio of titanium dioxide/zirconium dioxide, and amount of surfactant, to create the most reproducible results. Using cyclic voltammetric (CV) analysis, this study has proven that the novel titanium dioxide/zirconium dioxide can be utilized to detect heavy metals—lead and cadmium, at relatively low concentrations (7.6×10−6M and 1.1×10−5M for Pb and Cd, respectively) at optimum pH value (pH=3). From analyzing CV data the optimal electrodes surface area was estimated to be 0.028 (±0.003)cm2. Also, under the specific experimental conditions, electron transfer coefficients were estimated to be 0.44 and 0.33 along with the heterogeneous electron transfer rate constants of 5.64×10−3 and 2.42×10−3(cm/s) for Pb and Cd, respectively.

Characterization and electrochemical investigations of micellar/drug interactions

The effect of adding surface-active agents to electrolytes containing isoniazid (INH), an antituberculous drug, on the voltammetric response of carbon paste electrode (CPE) was studied. The enhancement of current signal due to the oxidation process was a function of the amount of analyte, pH of the medium, surfactants’ type, and chain length and aromaticity and accumulation time at the electrode surface. Eight surfactants were used, three anionic type, sodium dodecyl sulphate (SDS), sodium octyl sulphate (SOS) and sodium dodecyl benzene sulphonate (SDBS), three cationic type, cetyl trimethyl ammonium bromide (CTAB), trimethyl octyl ammonium bromide (TMOB) and cetyl pyridinium bromide (CPB) and two nonionic surfactants, albumin and Triton X-405. Addition of SDS and SDBS to the isoniazid-containing electrolyte was found to enhance the oxidation current signals while SOS showed an opposite effect. The addition of either the cationic or nonionic surfactants was found to decrease oxidation current signals. To confirm the interactions between surfactant and isoniazid, absorbance spectroscopy has been performed. NMR measurements gave a good expectation for the location and orientation of INH in different micelles and gave a similar conclusion to that obtained from electrochemical and UV–vis data. The use of SDS in the electrochemical determination of isoniazid using differential pulse voltammetry at carbon paste electrode improved the limit of detection to 6.29ngmL−1. The validity of using this method in the determination of drug active ingredient in tablet formulations was also demonstrated.

Ferrocenyl silicon-based dendrimers as mediators in amperometric biosensors

The application of ferrocene-containing dendrimers as mediators in amperometric biosensors is described. The steady-state amperometric response of carbon paste electrodes containing these dendritic relay systems and glucose oxidase is investigated as a function of the glucose concentration and the applied potential. The results show that these sensors respond rapidly to the addition of glucose. The dependence of the glucose sensor response on the size, the number of organometallic redox centers and the nature of the organosilicon dendritic framework is discussed.

Electrochemical response of a carbon paste electrode containing an adsorbed species on incorporated alumina

The electrochemical response of carbon paste electrode was investigated containing an inorganic and a non-electroactive compound on which an electro- active organic molecule was adsorbed. Alizarin S was chosen as the test molecule adsorbed on 150 m(2)/g of alumina, because this molecule is either easily reduced or oxidized on carbon. The electrode response was found to be linear for low amounts of alumina containing a known amount of Alizarin S. The electrical yield was never higher than 50%, but was reproducible. An increasing alumina amount in the paste increased the response, but lowered the electrical yield.

Altered response of carbon paste electrodes after contact with brain tissue: Implications for modified electrode use in vivo

Altered response of carbon paste electrodes after contact with brain tissue: Implications for modified electrode use in vivo