Nanomolar amperometric sensing of hydrogen peroxide using a graphite pencil electrode modified with palladium nanoparticles

We report on a simple and rapid method for the preparation of a disposable palladium nanoparticle-modified graphite pencil electrode (PdNP-GPE) for sensing hydrogen peroxide (H₂O₂). The bare and PdNP-modified GPEs were characterized by cyclic voltammetry and SEM. The two electrodes displayed distinct electrocatalytic activities in response to the electrochemical reduction of H₂O₂. The amperometric detection limits were 45 nM and 0.58 mM, respectively, for the PdNP-GPE and bare-GPE, at an S/N of 3. The electrodes can be prepared simply and at low cost, and represent a promising tool for sensing H₂O₂.

Enzyme-free amperometric sensing of hydrogen peroxide and glucose at a hierarchical Cu2O modified electrode

In this paper, an enzyme-free amperometric electrochemical sensor was fabricated by casting Nafion-impregnated Cu₂O particles onto a glassy carbon electrode. A dual dependence of peak current on sweeping rate, which can be attributed for the accumulation of reaction products, was observed on the sensor. Electrochemical analysis of the particulate Cu₂O for detecting H₂O₂ and glucose is described, showing remarkable sensitivity in both cases. The estimated detection limits and sensitivities for H₂O₂ (0.0039 μM, 52.3 mA mM⁻¹ cm⁻²) and glucose (47.2 μM, 0.19 mA mM⁻¹ cm⁻²) suggest that the response for H₂O₂ detection was much higher than for glucose detection. Electron microscopy observation suggested that the hierarchical structures of Cu₂O resulting from self-assembly of nanocrystals are responsible for the specific electrochemical properties.     

A glassy carbon electrode modified with SnO2 nanofibers,polyaniline and hemoglobin for improved amperometric sensing of hydrogen peroxide

Microchimica Acta - The authors describe a glassy carbon electrode (GCE) modified with a multiporous nanofibers prepared from SnO2, polyaniline and hemoglobin, and its application to the...     

An amperometric sensor for hydrazine based on nano-copper oxide modified electrode

A sensitive hydrazine sensor has been fabricated using copper oxide nanoparticles modified glassy carbon electrode (GCE) to form nano-copper oxide/GCE. The nano-copper oxide was electrodeposited on the surface of GCE in CuCl₂ solution at −0.4 V and was characterized by Scanning electron microscopy and X-ray diffraction. The prepared modified electrode showed a good electrocatalytic activity toward oxidation of hydrazine. The electrochemical behavior of hydrazine on nano-copper oxide/GCE was explored. The oxidative current increased linearly with improving concentration of hydrazine on nano-copper oxide/GCE from 0.1 to 600 μM and detection limit for hydrazine was evaluated to be 0.03 μM at a signal-to-noise ratio of 3. The oxidation mechanism of hydrazine on the nano-copper oxide/GCE was also discussed. The fabricated sensor could be used to determine hydrazine in real water.     

Dendrimer-rhodium nanoparticle modified glassy carbon electrode for amperometric detection of hydrogen peroxide

Metallic nanoparticles of rhodium were prepared by using the newly synthesized N,N-bis-succinamide-based dendrimer as stabilizers. The Rh nanoparticles were spherical shaped with a particle size of ∼2 nm. The dendrimer Rh-encapsulated nanoparticles (Rh-DENs) were immobilized on glassy carbon electrode (GCE) and their electrocatalytic activity towards hydrogen peroxide reduction was investigated using cyclic voltammetry and chronoamperometry. The Rh-DENs modified GCE showed excellent electrocatalytic activity for hydrogen peroxide reduction reactions. The steady-state cathodic current response of the modified electrode at −0.3 V (vs SCE) in phosphate buffer (pH 7.0) showed a linear response to hydrogen peroxide concentration ranging from 8 to 30 μM with a detection limit and sensitivity of 5 μM and 0.03103 × 10⁻⁶ A μM⁻¹, respectively.     

Voltammetric behaviour and amperometric sensing of hydrogen peroxide on a carbon paste electrode modified with ternary silver-copper sulfides containing intrinsic silver

Monatshefte für Chemie - Chemical Monthly - The electrochemical behavior of three ternary mixed silver-copper sulfides toward hydrogen peroxide, at various pH values, is presented....     

beta-Cyclodextrin-ferrocene inclusion complex modified carbon paste electrode for amperometric determination of ascorbic acid

Inclusion complex of ferrocene (Fc) with beta-cyclodextrin (beta-CD) has been synthesized in ethylene glycol. It was unsolvable in water and had been successfully used to the preparation of beta-CD-Fc inclusion complex modified carbon paste electrode (CFCPE). Solid paraffin was used as the binder of the electrode. Ascorbic acid (AA) was electrocatalytically oxidized at the electrode in NH(3)-NH(4)Cl buffer (pH 10.0) with a anodic peak potential of +0.20 V (vs. SCE). The anodic current was proportional to the concentration of AA in the range 1.0x10(-3)-5.0x10(-7) mol l(-1) with the detection limit of 1.0x10(-7) mol l(-1). Using the inclusion complex as the electroactive substance greatly increased the stability and reproducibility of CFCPE than using Fc; the lifetime of the electrode can be over 1 year. Because CFCPE responds rapidly and sensitively, it has been successfully applied to the determination of AA in fruit juices.     

Copper modified platinum electrode for amperometric detection of spectinomycin sulfate by anion-exchange chromatography

A La~(3+)-Cu/Pt modified electrode was fabricated by electrodepositing process in CuSO_4 solution by adding a small amount of lanthium compound,and it was employed for direct current(DC) amperometric detection of spectinomycin by anion-exchange chromatography.Without derivatization,this method can simultaneously determine the main component and impurities in spectinomycin pharmaceutical raw material.Ease of preparation,being applied in DC detection mode and good catalytic stability confirmed the interest...     

Benzoquinone modified electrode for sensing NADH and ascorbic acid

A benzoquinone modified basal plane pyrolytic graphite electrode shows electrocatalytic activity for the oxidation of NADH and ascorbic acid in phosphate buffer (pH 7.3). The modified electrode shows a linear variation of catalytic current with concentration in the range 1-10 mM for both NADH and ascorbic acid. The rate constants have been estimated from the surface coverage data.     

Mechanically immobilized nickel aquapentacyanoferrate modified electrode as an amperometric sensor for the determination of BHA

Nickel aquapentacyanoferrate (NAPCF), a novel transition metal complex has been prepared and its ability to act as an electrocatalyst for BHA oxidation has been demonstrated. The cyclic voltammetric behaviour of the NAPCF modified electrode prepared by mechanical immobilization on the graphite electrode was well defined. A pair of redox peaks corresponding to the electrochemical behaviour of the NAPCF was observed at 0.35 V and 0.31 V, corresponding to the anodic and cathodic peaks respectively, with a formal potential of 0.33 V. The NAPCF modified electrode favoured electrocatalytic oxidation of BHA to occur at a greatly minimized overpotential of 0.48 V. Experiments were performed to characterize the electrode as an amperometric sensor for the determination of BHA. The anodic peak current was linearly related to BHA concentration in the range of 6.24x10(-7) M to 2.19x10(-4) M with a detection limit of 2.49x10(-7) M and a correlation coefficient of 0.9979. Amperometry in stirred solution exhibited quick and sensitive response to BHA, showing the possible application of the modified electrode in flow system analysis. The modified electrode retained its initial response for more than 2 months when stored in supporting electrolyte, owing to the chemical and mechanical stability of the NAPCF mediator. This modified electrode was also quite effective in the determination of BHA in commercial samples.     

Carbon paste-tetrathiafulvalene amperometric enzyme electrode forthe determination of glucose in flowing systems

The development of a carbon paste-tetrathiafulvalene amperometric enzyme electrode for the determination of glucose in flowing streams is described. The enzyme electrode is operated in a flow-through detector based on the wall-jet configuration under flow injection (FI) and steady-state (SS) conditions. Under FI conditions, high precision (0.6%) and sample throughput (120 samples h-1) are possible. Moreover no pre-conditioning of the electrode is required. The flow system is suitable for the determination of glucose in whole blood without sample dilution. With proper orientation of the jet with respect to the enzyme electrode, high accuracy can be obtained under SS conditions.     

Flow injection amperometric determination of acetaminophen at a gold nanoparticle modified carbon paste electrode

An amperometric detector with a gold nanoparticle modified carbon paste electrode (GNMCPE) was applied applied to flow injection analysis for the determination of acetaminophen. An obvious shift of the peak potential and increase of the current peak were observed for the GNMCPE in comparison to that of the bare carbon paste electrode. The experimental conditions, such as species of buffer, pH, flow rate, detection volume, injection volume, and injection time were investigated. Under the optimized conditions, the calibration curve was obtained over the concentration range of 0.1–80 mg L^?1 of acetaminophen with a linear correlation coefficient of 0.9994. The detection limit (3σ) was estimated to be 0.05 mg L^?1 (n?=?7). The recoveries of acetaminophen were between 98.40% and 104.1%, and the relative standard deviation varied between 1.66% and 2.74% for the different samples. This method was applied to analyze six types of tablets obtained from a local drugstore. The contents of acetaminophen were found to be 0.498, 0.323, 0.249, 0.324, 0.319 and 0.323 g of each tablet, respectively. These results are consistent with the values obtained by high performance liquid chromatography.     

Flow injection-pulse amperometric detection of ephedrine at a cobalt phthalocyanine modified carbon paste electrode

Direct detection of ephedrines and other underivatized amino compounds (amines, alicyclic amines, alkanolamines, and amino acids) can be carried out via electrocatalytic oxidation at a carbon paste electrode (CPE) modified with cobalt phthalocyanine (CoPC) in alkaline solution (0.10 mol L-1 NaOH). Most of the amino compounds tested could be determined using the CoPC/CPE in an amperometric flow detector. The analytical signal of ephedrine was stabilised by alternating the potential between an anodic detection potential of +0.30 V (+0.45 V for other amino compounds) applied for 220 ms and a cathodic reactivation potential of -0.30 V applied for 100 ms (potentials versus SCE). The linear response range for ephedrine was within 1-100 mumol L-1 and the detection limit was 0.8 mumol L-1 with a 100 microL sample loop and a typical sampling ra 60 h-1. The signal (oxidation peak current) reproducibility was 2-3%. The method was applied to the determination of ephedrine in pharmaceutical formulations with results comparable to those obtained with a standard spectrophotometric method.     

Enhanced sensing of anthraquinone dyes using multiwalled carbon nanotubes modified electrode

The voltammetric behaviour of two anthraquinone dyes such as Alizarin Red S (ARS) and Reactive blue 4 (RB4) was investigated at plain glassy carbon electrode (GCE), multiwalled carbon nano tube modified GCE (MWCNT/GCE) and zeolite modified GCE (ZE/GCE) using cyclic voltammetry. Effects of pH, scan rate and concentration were studied. The surface morphology of the modified electrode in the absence and presence of dye molecules was characterized by scanning electron microscopy (SEM). A systematic study on the variation of experimental parameters with differential pulse stripping voltammetry (DPSV) was carried out and the optimized experimental conditions were arrived. MWCNT/GCE performed well among the three electrode systems and the limit of detection (LOD) was 0.036?µg?mL^?1 for ARS and 0.05?µg?mL^?1 for RB4 on this modified system. Suitability of the differential pulse stripping voltammetric method for the trace determination of textile dyes in effluents was also realized.     

Pulsed amperometric detection of underivatized amino acids using polypyrrole modified copper electrode in acidic solution

The successful pulsed amperometric detection of underivatized amino acids have been carried out in an acidic media on a polypyrrole (PPy) modified Cu electrode. The formation of PPy film doped with glutamate (glu) on a Cu electrode surface changes the mechanism of Cu dissolution. After application of multistep potential waveform, the PPy film was glu free due to the electro-reduction and overoxidation. High anodic potential polarization treatment yielded partially overoxidized PPy film as long as the Cu surface dissolution and amino acid permeation through the film was well controlled. This overoxidized PPy film acted as a charge and size exclusion barrier in order to improve the selectivity and stability of a Cu electrode. Various process parameters such as film modification time, detection and cleaning potential and pH of solution have been optimized to maximize the beneficial electrocatalytic properties of the electrode surface. At an optimized condition, detection limits for positively charged histidine and arginine are 19 and 22 pg respectively, whereas the neutral amino acids detected in amounts of 0.9–2.3 ng. Furthermore, the PPy coated Cu electrode response was long lived, stable and reproducible.     

An amperometric glucose biosensor based on the immobilization of glucose oxidase on the CuGeO3 nanowire modified electrode

A new amperometric biosensor based on adsorption of glucose oxidase (GOx) at the CuGeO₃ nanowires (NW) modified glassy carbon electrode (GCE) is reported in this article. The properties of the biosensor were characterized by Fourier transform infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS) and electrochemical techniques. The GCE modified with the CuGeO₃ NW/GOD showed excellent electrocatalytical response to the oxidation of glucose. Different parameters including GOx concentration, working potential and pH of supporting electrolyte that governed the analytical performance of the biosensor have been studied in detail and optimized. The biosensor was applied to detect glucose with a linear range of 0.5 to 7 mM. The biosensor exhibited excellent reproducibility and stability.