Electrochemical Characterization of Carbon Solidlike Paste Electrode Assembled Using Different Carbon Nanoparticles

Solid like carbon paste electrodes (SCPEs) are built using different carbon materials namely carbon black N110, N220, N375, N772 and acetylene black. The electrochemical behavior of these electrodes and the influence of carbon black/paraffin ratio were studied and the results were discussed and compared to other electrodes prepared with graphite, mesoporous carbon and nanopowder carbon. Cyclic voltammetry, amperometry and electrochemical impedance spectroscopy were employed for their electrochemical and analytical characterizations. Amperometric measurements using N110, N220, N375 SCPEs with solid paraffin, showed a linear response of benzoquinone concentration with a detection limit of 75, 32 and 171 nM respectively.     

Cysteine combined with carbon black as support for electrodeposition of poly (1,8-Diaminonaphthalene): Application as sensing material for efficient determination of nitrite ions

Poly 1,8-Diaminonaphtahlene/cysteine (poly 1,8-DAN/Cys) combined with carbon black (CB) nanoparticles are proposed as an excellent sensor for the detection of nitrite ions. To design the electrocatalyst, a simple approach consisting on drop-casting method was applied to disperse carbon black on the surface of glassy carbon electrode, followed by the immobilization of cysteine on the surface of CB nanoparticles. The electrochemical polymerization of 1,8-Diaminonaphthalene was conducted in acidic medium by using cyclic voltammetry. The prepared hybrid material was denoted poly 1,8-DAN /Cys/CB. Several methods were used to characterize the structural and electrochemical behavior of the reported hybrid material including Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), amperometry and differential pulse voltammetry (DPV). The prepared electrode displayed an outstanding electroactivity towards nitrite ions reflected by an enhancement in the intensity of the current and a decrease of the charge transfer resistance. Poly 1,8-DAN/Cys/CB displayed an excellent sensing performance towards the detection of nitrite with a very low detection limit of 0.25 µM. Two linear ranges of 1–40 µM and 20–210 µM when using amperometry and differential pulse voltammetry (DPV) were obtained respectively. This work highlights the simple preparation of a polymeric film rich in amine and thiol groups for nitrite detection.     

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)(10)Cl]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 microA/microM over the linear range 5 x 10(-8)-5 x 10(-4)M nitrite with a detection limit of 3 x 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.     

Ultralow Cost Electrochemical Sensor Made of Potato Starch and Carbon Black Nanoballs to Detect Tetracycline in Waters and Milk

Detection of traces from pharmaceutical drugs such as antibiotics in drinking water and foodstuff is essential for guaranteeing human health in some environments, and this has to be done with low cost technologies to be widely deployed in public services and industry. In this paper, we describe an ultralow cost (<US$ 0.005 per unit of sensing layer) electrochemical sensor to detect the antibiotic tetracycline, which is made of a homogeneous thin film of potato starch (PS) and carbon black (CB) deposited on glassy carbon electrodes (GCE). Detection of tetracycline was also performed in real samples consisting of tap water, river water, milk and in solutions prepared with commercial tablets of this medicine in the range between 5.0 and 120 μmol L⁻¹, with a detection and quantification limit of 1.15 and 4.47 μmol L⁻¹, respectively. The high sensitivity was attributed to the enhanced conductivity and larger surface area induced by incorporating the carbon black into potato starch. The CB‐PS/GCE electrodes were reproducible and stable, thus serving as a generic platform for detection of other antibiotics and hormones whose redox potentials are similar to those of tetracycline.     

基于不同工作电极的亚硝酸盐电化学传感器

亚硝酸盐是环境和生物循环中不可或缺的一部分,但其浓度超标不仅会污染环境,还会致癌。因此对亚硝酸盐实现高效、快速精密检测具有重要的科学和实际意义。基于电化学传感技术的污染物分析与检测已成为研究热点,尤其工作电极的选用和设计对提升响应速度、灵敏度、检测限及降低成本、简化操作等至关重要而备受研究者广泛关注。本文将以玻碳电极、碳糊电极、金属薄膜、聚合物薄膜及碳布电极为分类,针对亚硝酸盐的检测,详细综述基于不同电极的电化学传感器的研究进展。以期通过构建方法和电催化性能的对比为构建新型传感器提供理论与实际指导。     

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.     

Zeolite-modified solid carbon paste electrodes

New zeolite-modified carbon-based electrodes are described. They are based either on the physical anchoring of zeolite particles on the surface of solid carbon paste (the viscosity of which can be tuned by temperature change or controlled dissolution by an organic solvent), or on the dispersion of zeolite particles in the bulk of a carbon paste matrix containing solid paraffin as a binder. Both these systems display superior electrochemical performance in comparison to corresponding "classical" zeolite-modified carbon paste electrodes using mineral oil as binder. These well-described composites usually suffer from poor mechanical stability in stirred media as well as memory effects due to significant ingress of the external solution into the bulk electrode. Advantages of the zeolite-modified solid carbon paste electrodes are reported mostly on the basis of two electroanalytical applications: the voltammetric detection of Cu²⁺ ions after accumulation by ion exchange at open circuit, and the indirect amperometric detection of non-electroactive species (i.e. Na⁺) in flow injection analysis.     

Electrochemical Determination of Uric Acid,Dopamine and Tryptophan at Zinc Hexacyanoferrate Clay Modified Electrode

A Cameroonian smectite clay has been transformed into Zn²⁺ homoionic form and then used to prepare film modified glassy carbon electrodes and carbon paste electrodes. These electrodes containing Zn²⁺ were exploited to prepare a mixed valence zinc hexacyanoferrate (ZnHCF). Cyclic voltammetry has been employed to monitor the in situ growth of ZnHCF on clay modified electrodes. Although interesting electrocatalytic properties toward UA were observed with these modified electrodes, the modified carbon paste electrodes were the most suitable for dopamine, uric acid and tryptophan detection and exhibited for these analytes extended linear range, high sensitivities, selectivity and low limit.     

Two new manganese(II) complexes bulk-modified carbon paste electrodes: Preparation and electrocatalytic activities

Two new manganese complexes of [(2-py)CNOH]₂Cl₂ (1) and [(2-py)CNOH] ₂(OAc) ₂ (2) were synthesized and their structures were characterized by X-ray crystallography, IR spectroscopy and elemental analysis. Two complexes were used as bulk modifier to fabricate two carbon paste electrodes (Mn-CPE: 1-CPE and 2-CPE). The electrochemical behaviors of two modified electrodes were characterized by cyclic voltammetry. They have similar electrochemical behaviors and good electrocatalytic activities toward the reduction of hydrogen peroxide and nitrite. The results are reproducible with a lower detection limit than earlier reports. There exist a good linear relationship between peak current with the concentration in the range of 0.10?C1.20 ??M and a detection limit of 0.08 ??M for hydrogen peroxide, and in the range of 0.02?C0.10 ??M and a detection limit of 0.01 ??M for nitrite. Also Mn-CPE exhibits remarkable long term stability, simple preparation and inexpensive material, which is important for practical application on electrochemistry sensors.     

A comparative study of chromium(III) ion-selective electrodes based on N,N-bis(salicylidene)-o-phenylenediaminatechromium(III)

A comparative study was made between three types of Cr(III) ion-selective electrodes: PVC membrane electrode, silver coated electrode and modified carbon paste electrode based on N,N-bis(salicylidene)-o-phenylenediaminatechromium(III) complex (Crsalophen). As anticipated, electrodes with a solid contact, rather than a traditional liquid inner contact, give lower detection limits because of diminished ion fluxes. Often, however, ill-defined solid contact gives rise to instabilities and interferences by oxygen gas. The carbon paste electrode provides a more sensitive and stable device than that afforded by PVC and coated electrodes. The best performance was obtained by an electrode based on the paste containing 3.5 wt% Cr-complex, 48.5% graphite plasticized with a mixture of 24.0 wt% tris(2-ethylhexyl) phosphate (DOPh) + 24.0 wt% dioctyl sebacate (DOS). The sensor has a linear dynamic range of 7.5 × 10^-6 to 1.0 × 10^-2 M, with a Nernstian slope of 20.1 ± 0.6 mV decade^-1, and a detection limit of 1.8 × 10^-6. It has a short response time of a bout 8 s and is applicable in a pH range of 4.5-7.7. It was successfully used as an indicator electrode in potentiometric titration of Cr(III) with EDTA and in determination of Cr(III) in water samples and chromium in (Crsalophen).     

Lead ion sensor with electrodes modified by imidazole-functionalized polyaniline

Glassy carbon electrodes (GCE) and carbon paste electrodes (CPE) were modified with imidazole functionalized polyaniline with the aim to develop a sensor for lead (II) in both acidic and basic aqueous solution. The electrodes were characterized by cyclic voltammetry and differential pulse adsorptive stripping voltammetry. The limit of detections obtained with glassy carbon electrode and carbon paste electrode are 20?ng?mL^-1 and 2?ng?mL^-1 of lead ion, respectively. An interference study was carried out with Cd(II), As(III), Hg(II) and Co(II) ions. Cd(II) ions interfere significantly (peak overlap) and As(III) has a depressing effect on the lead signal. The influence of pH was investigated indicating that bare and modified GCE and CPE show optimum response at pH?4.0 ± 0.05.

Electrocatalytic amperometric determination of amitrole using a cobalt-phthalocyanine-modified carbon paste electrode

Cobalt-phthalocyanine-modified carbon paste electrodes are shown to be excellent indicators for electrocatalytic amperometric measurements of triazolic herbicides such as amitrole, at low oxidation potentials (+0.40 V). The detection and determination of amitrole in flow injection analysis with a modified carbon paste electrode with Co-phthalocyanine is described. The concentrations of amitrole in 0.1 M NaOH solutions were determined using the electrocatalytic oxidation signal corresponding to the Co(II)/Co(III) redox process. A detection limit of 0.04 microg mL(-1) (4 ng amitrole) was obtained for a sample loop of 100 microL at a fixed potential of +0.55 V (vs. Ag/AgCl) in 0.1 M NaOH and a flow rate of 4.0 mL min(-1). Furthermore, the modified carbon paste electrodes offers reproducible responses in such a system, and the relative standard deviation was 3.3% using the same surface, 5.1% using different surface, and 6.9% using different pastes. The performance of the cobalt-phthalocyanine-modified carbon paste electrodes is illustrated here for the determination of amitrole in commercial formulations. The response of the electrodes is stable, with more than 80% of the initial retained activity after 50 min of continuous use.     

NO-2的芯片毛细管电泳-修饰碳糊电极电化学检测

制备了3-巯丙基三甲氧基硅烷-铜(MPTMS-Cu)/MCM-41分子筛修饰碳糊电极,研究了该修饰电极对NO-2电化学还原的 电催化作用,分析了修饰物含量、溶液pH对电化学反应的影响。以该电极为检测电极,设计制作了芯片毛细管电泳-电化学 检测系统,探讨了NO-2的芯片毛细管电泳检测方法。以50 mmol/L醋酸钠(pH 5.8)为电泳缓冲液、分离电压为-1.6　kV时 ,检测可在40 s内完成。纯水中NO-2检测的线性浓度范围为10.0～5000.0 μmol/L,检出限为4.0 μmol/L。     

碳糊电极在硫化矿发电浸出过程中的应用研究

应用线性电势扫描法研究硫化矿的纯矿电极与碳糊电极体系在氯化钠电解液中的电化学行为.结果表明,乙炔黑在硫化矿浸出过程中起到电催化作用,加入乙炔黑的碳糊电极较之纯矿电极,其发电浸出输出电流和电压均有一定程度的增加,同时活化能较传统浸出的低.     

Comparison of different carbon nanostructures influence on potentiometric performance of carbon paste electrode

Recently, different carbon nanomaterials were introduced for construction of electrochemical sensors. In this study, the influence of carbon nanomaterial on performance of carbon paste potentiometric electrode was investigated. In this manner, different kinds of carbon nanomaterial, i.e., graphene, graphene oxide and carbon nanotube (CNT) were used as a conduction phase in carbon paste electrode. Then, potentiometric characteristics of the corresponding paste electrodes such as calibration slope, linear range, detection limit, response time and stability were compared with each other. The results appeared comprehensive findings about the role of electrode’s content in electrochemical performance.     

Amperometric detection of glucose using self-catalytic carbon paste electrodes

The analytical detection of d-glucose by means of self-catalytic carbon paste electrodes is described. In the construction of these electrodes, carbon powder has been modified with the redox liquid n-butylferrocene, which simultaneously serves both to help bind the paste together whilst also acting as a mediator in the enzymatic oxidation of d-glucose by glucose oxidase. The sensor then functions by monitoring the electrochemical oxidation of the constituent n-butylferrocene itself. Through testing in model glucose solutions, the electrodes were found to yield a linear response over a d-glucose concentration range of 2-20 mM. They were also successfully employed in the determination of d-glucose levels in a spiked blood sample, giving a detection limit of 0.8 mM (based on the 3sigma criterion).     

聚铬黑T修饰电极检测亚硝酸盐的研究

利用电化学聚合法将铬黑T修饰到玻碳电极表面,制得聚铬黑T修饰电极。该修饰电极对亚硝酸盐的电化学氧化具有明显的催化作用,这种催化作用主要是由于聚铬黑T薄膜与带负电荷的亚硝酸盐离子的静电相互作用,导致亚硝酸盐离子富集在电极表面/溶液界面,显著增强了亚硝酸盐的氧化电流。电子传输系数α为0.735。选用0.85V作为工作电压,对亚硝酸盐进行安培检测,在0.05μmol/L～1.0 mmol/L和1.0～20.0 mmol/L两个浓度范围内呈现良好的线性关系,检测限达到0.01μmol/L。且该修饰电极有良好的重现性和稳定性。将该修饰电极用于泡菜中亚硝酸盐的测定,获得了满意的结果。     

Development of a Novel Molecularly Imprinted Polyvinylimidazole/Functionalized Carbon Black Nanocomposite-based Paste Electrode for Electrochemical Sensing of Imazethapyr in Rice Samples

This paper reports the development of a simple electroanalytical method for imazethapyr (IMT) determination in rice samples based on molecularly imprinted polymer and functionalized carbon black paste electrode (MIP-fCBPE). Carbon black (CB) was functionalized by the insertion of oxygenated functional groups upon acid treatment with HNO₃ and H₂SO₄. The functionalized carbon black (fCB) presented higher performance for IMT determination than the CB without functionalization. The insertion of molecularly imprinted polyvinylimidazole (MIP-VN) in the fCBPE promoted a significant increase in the cathodic peak current even at low proportions (7.5 % w/w) due to the specific binding sites for IMT recognition. For IMT determination, DPV parameters were optimized by the Doehlert matrix applying 0.1 V for 60 s as pre-treatment in acetate buffer solution (pH 3.0) as supporting electrolyte. The proposed method showed low limit of detection (0.03 μmol L⁻¹), a wide linear range (0.10–70.00 μmol L⁻¹), and good precision in terms of repeatability of intraday measures (RSD%=3.6). The method was applied in rice samples after microwave-assisted extraction of IMT and the accuracy of the method was evaluated by addition/recovery assays (96.3–105.7 %), being statistically attested using HPLC-DAD as reference technique.     

Nitrite Oxidation with Copper–Cobalt Nanoparticles on Carbon Nanotubes Doped Conducting Polymer PEDOT Composite

Copper–cobalt bimetal nanoparticles (Cu?Co) have been electrochemically prepared on glassy carbon electrodes (GCEs), which were electrodeposited with conducting polymer nanocomposites of poly(3,4‐ethylenedioxythiophene) (PEDOT) doped with carbon nanotubes (CNTs). Owing to their good conductivity, high mechanical strength, and large surface area, the PEDOT/CNTs composites offered excellent substrates for the electrochemical deposition of Cu?Co nanoparticles. As a result of their nanostructure and the synergic effect between Cu and Co, the Cu?Co/PEDOT/CNTs composites exhibited significantly enhanced catalytic activity towards the electrochemical oxidation of nitrite. Under optimized conditions, the nanocomposite‐modified electrodes had a fast response time within 2 s and a linear range from 0.5 to 430 μm for the detection of nitrite, with a detection limit of 60 nm . Moreover, the Cu?Co/PEDOT/CNTs composites were highly stable, and the prepared nitrite sensors could retain more than 96 % of their initial response after 30 days.     

Carbon paste-based electrochemical detectors for microchip capillary electrophoresis/electrochemistry

The first reported use of a carbon paste electrochemical detector for microchip capillary electrophoresis (CE) is described. Poly(dimethylsiloxane) (PDMS)-based microchip CE devices were constructed by reversibly sealing a PDMS layer containing separation and injection channels to a separate PDMS layer that contained carbon paste working electrodes. End-channel amperometric detection with a single electrode was used to detect amino acids derivatized with naphthalene dicarboxaldehyde. Two electrodes were placed in series for dual electrode detection. This approach was demonstrated for the detection of copper(II) peptide complexes. A major advantage of carbon paste is that catalysts can be easily incorporated into the electrode. Carbon paste that was chemically modified with cobalt phthalocyanine was used for the detection of thiols following a CE separation. These devices illustrate the potential for an easily constructed microchip CE system with a carbon-based detector that exhibits adjustable selectivity.