Use Of Carbon Paste Electrode Research Articles

Fabrication of a graphite-paraffin carbon paste electrode and demonstration of its use in electrochemical detection strategies.

Electrochemical detection methods hold many advantages over their optical counterparts, such as operation in complex sample matrices, low-cost and high volume manufacture and possible equipment miniaturisation. Despite these advantages, the use of electrochemical detection is currently limited in the clinical setting. There is a wide range of potential electrode materials, selected for optimal signal-to-noise ratios and reproducibility when detecting target analytes. The use of carbon paste electrodes (CPEs) for electrochemical detection can be limited by their analytical performance, however they remain very attractive due to their low cost and biocompatibility. This paper presents the fabrication of an easy-to-make and use graphite powder/paraffin wax paste combined with a substrate produced via additive manufacturing and confirms its functionality for both direct and indirect electrochemical measurements. The produced CPEs enable the direct voltammetric detection of hexaammineruthenium(III) chloride and dopamine at an experimental limit of detection (ELoD) of 62.5 μM. The key inflammatory biomarker Interleukin-6 through an enzyme-linked immunosorbant assay (ELISA) was also quantified, yielding a clinically-relevant ELoD of 150 pg ml-1 in 10% human serum. The performance of low-cost and easy-to-use CPEs obtained in 0.5 hours is showcased in this study, demonstrating the platform's potential uses for point-of-need electroanalytical applications.

Use of carbon paste electrode and modified by gold nanoparticles for selected macrolide antibiotics determination as standard and in pharmaceutical preparations

In this work, carbon paste electrode (CPE) and carbon paste electrode modified with gold nanoparticles (AuNPs/CPE) were employed with rapid direct anodic square wave voltammetry (SWV) for macrolide antibiotics erythromycin ethylsuccinate (EES), azithromycin (AZI), clarithromycin (CLA) and roxithromycin (ROX) determination. The surface of working electrodes was morphologically characterized by scanning electron microscopic (SEM) measurements whereby the presence of randomly distributed AuNPs of 10 nm diameter size on CPE surface was confirmed by energy dispersive spectrometer (EDS). SWV determination of four macrolide antibiotics using CPE was performed in aqueous Britton-Robinson buffer solutions (pH 2.0 to 11.98) showing that oxidation signals strongly depend upon pH (at pH ≥ 6) and exhibited the most favorable characteristics at pH 8.0 in the case of EES and pH 11.98 in the case of AZI, CLA and ROX. Under optimized conditions, the SWV method using CPE enables determination of all investigated macrolide antibiotics in low μg mL−1 concentration ranges with relative standard deviations (RSDs) lower than 6% and achieved detection limits (LODs) as 0.18, 0.045, 1.43 and 0.30 μg mL−1 for EES, AZI, CLA and ROX, respectively. In the case of AZI and ROX, it was demonstrated that the use of AuNPs/CPE as working electrode could additionally improve the results obtained with the SWV method concerning exhibited sensitivity, reproducibility and linear concentration range, due to the electrocatalytic properties of synthesized AuNPs. The optimized experimental parameters with the use of SWV method and CPE or AuNPs/CPE were successfully applied for determination of ROX and AZI in their pharmaceutical preparations Runac® and Hemomycin®, respectively. The reliability of the elaborated procedures and thus the accuracy of the obtained results were validated by comparing them with those obtained by means of HPLC-DAD measurements.

Electrochemical study of silver telluride (Ag2Te): anodic and cathodic potential dependent-reactions in alkaline cyanide solutions

Although electrochemical characterization has been used to elucidate the species formed during hydrometallurgical processes, it has not been commonly applied to the cyanidation of precious metal tellurides. In this study, voltammetric characterization of the silver telluride (Ag2Te) reaction system in alkaline cyanide solutions (pH 10.9 and 1250 mg/L CN−) was carried out making use of carbon paste electrodes. For this purpose, the electrochemical reactions system of elemental silver and elemental tellurium were first studied by cyclic voltammetry in two aqueous media (i.e., aqueous solution at pH 10.9, and 1250 mg/L CN− at pH 10.9) and, by comparing the cyclic voltammograms obtained with those for Ag2Te, the electrochemical reaction system was elucidated. The results obtained showed that the anodic oxidation of Ag2Te in alkaline cyanide solutions occurred by at least two consecutive steps according to:Step 1 (fast reaction): Ag2Te + 4CN− ↔ Te + 2Ag(CN)2− + 2e−.Step 2 (slow reaction): Te + 3H2O ↔ TeO32− + 6H+ + 4e−while the cathodic reduction of Ag2Te in alkaline cyanide solutions occurred according to:Ag2Te+2e−↔2Ag+Te2−

Use of carbon paste electrodes as a novel strategy to study adsorption mechanism of silver ions onto functionalized grapefruit peel

In order to study the adsorption mechanism of silver ions onto adsorbents prepared from grapefruit peels functionalized with urea and melamine, carbon paste electrodes (CPE) were prepared and cyclic voltammetry studies were carried out. The electrochemical results showed that for the case of CPE containing the adsorbent functionalized with urea, there is one oxidation signal at 0.0 V vs. MSE attributable to the oxidation of silver that was adsorbed onto the amino groups present on its surface. On the other hand, in the CPE that contained the adsorbent functionalized with melamine, two oxidation signals were observed at 0.0 V and −0.1 V vs. MSE attributable to silver adsorbed to the surface, but indicating the presence of two different energy adsorption sites: The first of them associated with amino groups and the second with carboxyl groups. The results were complemented with infrared spectroscopy techniques, X-ray photoemission spectroscopy, and dispersive energy spectroscopy and immersion microcalorimetry. From the results obtained it was possible to define the mechanism of adsorption of the metal on each of the adsorbents studied. The electrochemical study has provided valuable information to elucidate the mechanism of adsorption, adequately complemented with conventional spectroscopic techniques has achieved a broad characterization of the amino-functionalized organic matrix, so that this analytical technique is shown as a new alternative to study superficial chemical changes in functionalized materials.

Use of carbon paste electrodes for the voltammetric detection of silver leached from the oxidative dissolution of silver nanoparticles

The widespread use of silver nanoparticles (Ag NPs) in consumer goods has raised concerns about the release of silver in environmental waters. Of particular concern is the oxidative dissolution of Ag NPs to release Ag+ ions, which are highly toxic to many aquatic organisms. Here, we have investigated the application of differential pulse stripping voltammetry (DPSV) with carbon paste electrodes (CPEs) in monitoring the oxidation of Ag NPs. Using a commercially available, unmodified carbon paste and 60-s deposition times, a detection limit of 3 nM Ag+ could be achieved. We demonstrate its selectivity for free Ag+ ions over Ag nanoparticles, allowing for analysis of the oxidation of Ag NPs without the need for separation of ions and nanoparticles prior to analysis. We applied this approach to investigate the effect of pH in the oxidative dissolution of Ag NPs, demonstrating the usefulness of CPEs in studies of this type.

Use of Carbon Paste Electrode Modified with Biomass for Studying the Equilibria, Kinetics, and Proton Exchange Processes Associated with Bioaccumulation

AbstractThe sorption of Cd2+ onto nonliving Typha latifolia roots was investigated using carbon paste electrodes modified with a powder formed from the ground dried root. The equilibria, kinetics, and proton exchange processes associated with the biosorption process were determined. Cd2+ was found to accumulate on the root‐modified electrode under open circuit conditions, and the electrode was transferred to an electrochemical cell for square wave anodic stripping voltammetry measurements. The measured currents were proportional to the amount of Cd2+ adsorbed onto the root, which permitted the biosorption process to be measured as a function of cadmium solution concentration, time, and pH. The equilibrium values were fit to the Langmuir or Freundlich equations, and that the Langmuir isotherm model was found to provide a better fit than the Freundlich model. The pH‐dependent sorption curves showed that the accumulation of cadmium proceeded with proton exchange, and each adsorbed cadmium ion resulted in expulsion of two protons. The sorption kinetics were studied, the data obtained were fit to two models: a pseudo‐second‐order model and an intraparticle diffusion model. The pseudo‐second‐order model provided the best description of the bioadsorption data. These results indicated that these methodologies have clear advantages over existing methods, because the amount of reagents and sorbent used for the experiments are much less than are required for batch experiments.

Characterization of a carbon paste electrode modified with tripolyphosphate-modified kaolinite clay for the detection of lead

We report about the use of carbon paste electrode modified with kaolinite for analytical detection of trace lead(II) in domestic water by differential pulse voltammetry. Kaolinite clay was modified with tripolyphosphate (TPP) by impregnation method. The results show that TPP in kaolinite clay plays an important role in the accumulation process of Pb(II) on the modified electrode surface. The electroanalytical procedure for determination of Pb(II) comprised two steps: chemical accumulation of the analyte under open-circuit conditions, followed by electrochemical detection of the pre-concentrated species using differential pulse voltammetry. The analytical performance of this system has been explored by studying the effects of preconcentration time, carbon paste composition, pH, supporting electrolyte concentration, as well as interferences due to other ions. The calculated detection limit based on the variability of a blank solution (3sb criterion) for 10 measurements was 8.4×10−8molL−1, and the sensitivity determined from the slope of the calibration graph was 0.910molL−1. The reproducibility (RSD) for five replicate measurements at 1.0mgL−1 lead level was 1.6%. The results indicate that this electrode is sensitive and effective for the determination of Pb2+.

Electrochemical kinetic study of amperometric hydrogen peroxide biosensor fabricated using SBR

When rubber solution was used as a binder of carbon powder, the fast volatility of its solvent, toluene, assured the mechanical solidity of the carbon paste electrode just after electrode fabrication. This utility of the rubber binder met qualifications for the practical use of carbon paste electrodes and heightened morale to design a new enzyme electrode bound with SBR. In an attempt to evaluate the possibilities for practical use of the electrode, its electrochemical kinetic parameters, e.g. the symmetry factor (0.41), the exchange current density ( i 0, 4.62 × 10 −7 A/cm 2), the capacitance of double layer ( C d, 8.1 × 10 −6 F), the time constant ( τ A, 0.019 s), the maximum current ( i max, 9.80 × 10 −5 A/cm 2), the Michaelis constant ( K M, 4.24 × 10 −3 M), the diffusion constant ( D 1/2, 1.59 × 10 −6 cm/s 1/2) of the substrate, and other factors were investigated. Results show that SBR is a desirable binder of carbon powder.

부타디엔 고무로 결합된 탄소반죽 바이오센서를 이용한 과산화수소의 전기화학적 정량

When polybutadiene dissolved in toluene was a binder of carbon powder, the volatility of solvent just after electrode fabrication assured the mechanical solidity of the carbon paste electrode. This characteristic met the qualifications for practical use of carbon paste electrodes. A new enzyme electrode bound with butadiene rubber was constructed. In order to confirm whether it shows quantitative electrochemical behaviors or not, its electrochemical kinetic parameters, e.g. the symmetry factor, the exchange current density, the capacitance of double layer, the time constant, the maximum current, the Michaelis constant and other factors were investigated. These experimental facts showed that butadiene rubber is a recommendable binder for practical use of a carbon paste electrode.

Electrochemical Investigation of Animal Tissue Embedded Biosensor Bound with Ethylene-Propylene Rubber

When rubber dissolved in toluene was used as a binding material of graphite powder, the mechanical robustness of the carbon paste was guaranteed by the fast volatility of the solvent immediately after electrode construction. This cha-racteristic of the rubber solution met qualifications for practical use of carbon paste electrodes and enabled the design of a new enzyme electrode bound with EPDM. In order to confirm whether the electrode shows quantitative electrochemical behaviors or not, its kinetic parameters, e. g. the symmetry factor (0.2), the exchange current density (3.66 µA/cm

Optimization of the use of carbon paste electrodes (CPE) for electrochemical study of the chalcopyrite

The use of carbon paste electrodes (CPE) of mineral sulfides can be useful for electrochemical studies to overcome problems by using massive ones. Using CPE-chalcopyrite some variables were electrochemically evaluated. These variables were: (i) the atmosphere of preparation (air or argon) of CPE and elapsed time till its use; (ii) scan rate for voltammetric measurements and (iii) chalcopyrite concentration in the CPE. Based on cyclic voltammetry, open-circuit potential and electrochemical impedance results the recommendations are: oxygen-free atmosphere to prepare and kept the CPE until around two ours, scan rates from 10 to 40 mV s-1, and chalcopyrite concentrations > 20%.

Electrochemical modulation of the ligand properties of organically modified mesoporous silicas

A “soft” electrochemical method has been developed to deprotonate propylammonium-functionalised mesoporous silica particles and to exploit the resulting amine-functionalised material in carbon paste electrodes in the “open-circuit accumulation–voltammetric detection” sequence, using Cu(II) as the target analyte. The method is based on shifting the ammonium-amine acid–base equilibrium to the right via the electrochemical reduction of protons arising from the dissociation of ammonium moieties in aqueous medium. This approach is less destructive than the “classical” chemical deprotonation involving the use of hydroxide ions, resulting in much higher sensitivity with respect to Cu(II) preconcentration and detection. Possible generalisation of the electrochemically induced improvement of the binding properties of silica-based organic–inorganic hybrids was then illustrated through the use of carbon paste electrodes modified with carnosine-functionalised silica applied to Cu(II) detection with enhanced sensitivity and selectivity.

Carbon paste electrodes: correlation between the electrochemical hydrogen storage capacity and the physicochemical properties of carbon blacks

The difficulties in the use of carbon paste electrodes to quantify the electrochemical adsorption of hydrogen in nanocarbon materials are described. Chronoamperometry studies using a Ferro/Ferri redox couple were performed to obtain the electrochemical active area of paste electrodes prepared by dispersion of differing samples of carbon blacks (CB) within silicon oil. This electrochemical active area was combined with the BET-surface area of the carbon blacks, to obtain the mass of superficial carbon involved in the electrochemical processes. To assure equal conditions for comparison, the electronic conductivity of the paste was equivalent in all the samples. From our results it appears that cyclic voltammetry, combined with carbon paste electrodes and nitrogen adsorption isotherms, provides a simple and less expensive route for the qualitative evaluation of the electrochemical hydrogen uptake of novel carbon materials. Still, for quantitative measurements, some issues remain unsolved in highly structured carbons, where the lack of penetration of the bulky Ferro/Ferri redox couple in the micropores of the CB and the occurrence of solid-state diffusion cause the underestimation of the mass involved in hydrogen adsorption.

Electrochemiluminescence of dichlorotris (1,10-phenanthroline) ruthenium (II) with peroxydisulfate in purely aqueous solution at carbon paste electrode

The electrochemiluminescence (ECL) of dichlorotris (1,10-phenanthroline) ruthenium (II) [Ru phen 3 2+ ] with peroxydisulfate (S 2O 8 2−) was first described. The use of carbon paste electrodes, organic solvent modified electrodes, allowed obtaining ECL in purely aqueous solution. The ECL produced by the reaction of electrogenerated Ru phen 3 + with the strongly oxidizing intermediate SO 4 −·, was observed only when the applied potential was negative enough to reduce Ru phen 3 2+ . In comparison with Ru bpy 3 2+ /S 2O 8 2− ECL, the Ru(phen) 3 2+/O 8 2−/S 2O 8 2− ECL was more stable in aqueous solution. It was not affected by the storage of the carbon paste electrodes, and it quenched only at quite high S 2O 8 2− concentrations. The ECL intensity was a function of S 2O 8 2− concentration, increasing linearly with the S 2O 8 2− concentration from 5×10 −6 to 2×10 −3 mol l −1, and dropping off sharply at S 2O 8 2− concentration higher than 20 mmol l −1. The proposed ECL method with Ru phen 3 2+ was sensitive and selective for the determination of S 2O 8 2−.

The use of carbon paste electrode in the direct voltammetric determination of tryptophan in pharmaceutical formulations

A simple, fast and sensitive method is proposed for Tryptophan (Trp) determination in pharmaceutical formulations containing other non-electroative aminoacids, vitamins and hydroxycobalamines. Optimized conditions for differential pulse voltammetry allowed the determination of Trp with detection limit of 1.7 μM in 2–30 mM linear dynamic range ( n=7; r=0.999), at a bare, non-treated carbon paste electrode. Ascorbic acid interference was evaluated and eliminated by choosing a suitable baseline for determination of peak currents for Trp.

An electrochemical study of galena concentrate in perchlorate medium at pH 2.0: the influence of chloride ions

An electrochemical study of galena flotation concentrates in solutions of perchlorate and chloride ions at pH 2 has been carried out, through the use of carbon paste electrodes and cyclic voltammetry. The analysis of the voltammetric results indicates that in perchlorate solutions the galena is oxidized forming several products dependent on the applied potential. When the potential is below to 0.54 V/saturated calomel electrode (SCE), Pb(II) and elementary sulfur are formed. Galena oxidation to higher oxidation state of sulfur (e.g. thiosulfate and sulfate) requires a higher overpotential ( E>0.8 V vs. SCE), in the presence of perchloric acid, while in chloride medium a considerable lower overpotential is needed. From this reaction, the Pb(II) reacts with the chloride ions in order to form a lead–chloride complex that could precipitate depending on the concentration of chloride in solution and also could remain adsorbed on the galena particle surface. In the chloride media, the galena is reduced into metallic lead and hydrogen sulfide.

The use of carbon paste electrodes with non-conducting binder for the study of minerals: Chalcopyrite

A pulverized chalcopyrite mixture with graphite and silicon was subjected to electrochemical studies and found to have similar behaviour to that of chalcopyrite massive electrodes, with the advantage of excellent reproducibility, since the problems of polishing deficiency, fracture and lack of homogeneity that solid electrodes present, are avoided. From voltammetric studies of these carbon paste-chalcopyrite electrodes in H 2SO 4, HNO 3 and HCl media, it has been established that the reduction process is limited by the diffusion of protons to the interface. This study also shows that the increase of chloride ion concentration energetically favours the chalcopyrite reduction process, allowing for the separation of the processes of formation of chalcocite and bornite. On the other hand, this study also shows a reversible oxidation of the bornite and chalcocite obtained in the previous chalcopyrite reduction.

Carbon paste electrodes in mineral processing: an electrochemical study of galena

Electrochemical theories are often used to explain leaching of sulphide minerals and it is therefore desirable to study the individual processes with electrochemical methods. For good conducting minerals this comprises no difficulties since the mineral itself can be used as an electrode. However, for poorly conducting minerals this is not possible and direct electrochemical measurements cannot be performed. The aim of the present study was to examine the applicability of the carbon paste electrode technique to mineral processing. The mineral is embedded in graphite and the reaction at the heterogeneous electrode/electrolyte interface is investigated. In order to quantify the use of carbon paste electrodes a conducting mineral was chosen: galena. This makes a critical comparison of the electrochemical properties of the carbon paste-galena electrode and pure galena electrode possible. Potentiodynamic sweeps in acidic perchlorate solutions and with both stationary and rotating disk electrodes were used for the qualitative examination. In order to investigate the nature of the overall anodic dissolution reaction of galena, chronocoulometry in conjunction with atomic absorbance spectrometry was used. It was exclusively shown that the electrochemical behaviour of the carbon paste-galena system was the same as for pure galena. The overall anodic dissolution reaction involves two electrons and the stoichiometry of the galena sample was determined to be Pb 1.1S.

Determination of nitrite based on mediated oxidation at a carbon paste electrode modified with a ruthenium polymer

The use of carbon paste electrodes modified with [Ru(bpy) 2(PVP) 10Cl]Cl for the mediated detection of nitrite is described. This surface modifier substantially lowers the overpotential for nitrite oxidation, hence permitting its determination at a lower potential. Various electrode characteristics were optimized, including the modifier loading and the monitoring potential, using batch amperometry. Standard calibration curves yielded slopes of 0.30 μA/μ M over the linear range 5 × 10 −8−5 × 10 −4 M nitrite with a detection limit of 3 × 10 −8 M (1.38 ppb) nitrite. The modified electrode response was shown to be relatively stable over a period of 5 days with a signal diminution of 8%. Electrode-to-electrode precision was measured as 11.4%. Flow-injection studies indicated the suitability of this electrode as a detector in flowing streams.

L'electrode a Pate de Carbone Modifiee Son Utilisation en Voltammetrie par Redissolution Anodique a Impulsions Differentielles en Presence d'Un Film de Mercure

Abstract The various problems which are associated with the use of carbon paste electrode as thin mercury film electrode (TKFE) for anodic stripping voltammetry (ASV) can be overcame in a very easy and rapid way. The procedure consists to coat the carbon paste surface by spraying a graphite based conductive solution. For example, the dispersion of colloidal graphite in a mixture of methyl polymethacrylate with butyl acetate (as solvent) gives interesting results. Such a surface is easily renewable and the electrode does not require any pretreatment procedure like cleaning or polarization cycles…, after coating. The technique offers the advantage to limit the risk of sample contamination and memory effects. After pulverisation, a hard, uniform and compact layer is formed after evaporation of the solvent excess. The resulting electrode, electrochemically coated with mercury, exhibits a good stability as shown for the differential pulse anodic stripping voltammetry (DPASV) for cadmium ions. Replicate measurements were carried out in two different buffers at pH 8.5 and 5.0. Compared to the originally carbon paste electrode, a marked improvement of the reproducibility of the peak currents is observed. Calibration curves obtained by using the method of standard additions show a good linear relationship between cadmium ions concentration and peak current (down to 4×10−10 M.L−1). After a deposition time of 10 minutes, the detection limit for cadmium is 1×10−10 M.L−l in both media).