Preparation and Characterization of Graphite-Epoxy Composite Modified with Zinc Hexacyanoferrate and Their Electrochemical Behaviour in Presence of Substituted Anilines

The growth of zinc hexacyanoferrate (ZnHCF) hybrid film on the surface of graphite-epoxy composite (GEC) electrodes was demonstrated by cyclic voltammetry. Surface morphology of the hybrid film was investigated by using scanning electron microscopy. The effect of the type of monovalent cations on the redox behaviour of hybrid film was also studied. This effect indicated that the radius of the hydrated cation mainly determines the ion permeability of the film.The electrochemical behavior of the substituted anilines (procaine and sulfamerazine) in 1 M KCl of the modified GEC electrode showed a decrease of the cathodic currents while increasing the concentration of these analytes. The developed sensor also showed excellent stability for long time usage, higher sensitivity and cost-effective fabrication.

Determination of atenolol in environmental water samples and pharmaceutical formulations at a graphite-epoxy composite electrode

A bare graphite-epoxy composite was evaluated as an electrode material in the determination of atenolol in natural water samples and pharmaceutical formulations for which the analyte was spiked. Using a DPV procedure, a linear response was observed in the 4.45-84.7 mu mol L-1 range with a LOD = 2.23 mu mol L-1, without need of surface renewal between successive runs, and recoveries between 92.5 and 107.5% for pharmaceutical formulations. The results obtained from the proposed procedure agreed with HPLC results within a 95% confidence level. During the determination of atenolol in water samples, recoveries between 96.1 and 102.6% were found.

Desenvolvimento, caracterização e aplicação eletroanalítica de um compósito fluido de adesivo epóxi, grafite e ciclo-hexanona

A fluid conducting composite material prepared from graphite powder, commercial epoxy resin Araldite®, and cyclohexanone has been developed. The composition was optimized considering the mechanical properties as conductivity and adhesiveness using response surface methodology. This work employed cyclic voltammetry and amperometry to investigate the characteristics of such composite electrodes without and with the insertion of Prussian blue in the electrode body (bulk modified electrode). The composite electrodes were also successfully used for the amperometric detection of hydrogen peroxide at 0.0V vs Ag/AgCl.

Determination of paracetamol at a graphite-polyurethane composite electrode as an amperometric flow detector

A bare graphite-polyurethane composite was evaluated as an amperometric flow injection detector in the determination of paracetamol (APAP) in pharmaceutical formulations. A linear analytical curve was observed in the 5.00 x 10-5 to 5.00 x 10-3 mol L-1 range with a minimum detectable net concentration of 18.9 µmol L-1 and 180 determinations h-1, after optimization of parameters such as the detection potential, sample loop volume, and carrier solution flow rate. Interference of ascorbic acid was observed, however, it was possible overcome the interference, reaching results that agreed with HPLC within 95% confidence level. These results showed that the graphite-polyurethane composite can be used as an amperometric detector for flow analysis in the determination of APAP.

Interlaminar fracture characterization of a carbon-epoxy composite in pure mode II

The interlaminar fracture toughness in pure mode II (GIIc) of a Carbon-Fibre Reinforced Plastic (CFRP) composite is characterized experimentally and numerically in this work, using the End-Notched Flexure (ENF) fracture characterization test. The value of GIIc was extracted by a new data reduction scheme avoiding the crack length measurement, named Compliance-Based Beam Method (CBBM). This method eliminates the crack measurement errors, which can be non-negligible, and reflect on the accuracy of the fracture energy calculations. Moreover, it accounts for the Fracture Process Zone (FPZ) effects. A numerical study using the Finite Element Method (FEM) and a triangular cohesive damage model, implemented within interface finite elements and based on the indirect use of Fracture Mechanics, was performed to evaluate the suitability of the CBBM to obtain GIIc. This was performed comparing the input values of GIIc in the numerical models with the ones resulting from the application of the CBBM to the numerical load-displacement (P-) curve. In this numerical study, the Compliance Calibration Method (CCM) was also used to extract GIIc, for comparison purposes.

Determination of hydroquinone in a square wave voltammetry procedure using a graphite-polyurethane composite electrode

In order to a better characterization of a graphite-polyurethane composite intended to be used as a voltammetric sensor, the performance in a square wave voltammetric procedure was investigated. Using hydroquinone (HQ) as a probe, the electrode showed to be useful in square wave voltammetry with limit of detection of 0.28 µmol L-1, with recoveries between 99.1 and 101.5%. The results of the proposed method agreed with HPLC ones within 95% confidence level.

A Graphite-Polyurethane Composite Electrode for the Analysis of Furosemide

A graphite-polyurethane composite electrode has been used for the determination of furosemide, a antihypertensive drug, in pharmaceutical samples by anodic oxidation. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the electrooxidation process at +1.0 V vs. SCE over a wide pH range, with the result that no adsorption of analyte or products occurs, unlike at other carbon-based electrode materials. Quantification was carried out using cyclic voltammetry, differential pulse voltammetry, and square-wave voltammetry. Linear ranges were determined (up to 21 mu mol L-1 with cyclic voltammetry) as well as limits of detection (0.15 mu mol L-1 by differential pulse voltammetry). Four different types of commercial samples were successfully analyzed. Recovery tests were performed which agreed with those obtained by spectrophotometric evaluation. The advantages of this electrode material for repetitive analyzes, due to the fact that no electrode surface renewal is needed owing to the lack of adsorption, are highlighted.

Electrochemical Behavior of Verapamil at Graphite-Polyurethane Composite Electrodes: Determination of Release Profiles in Pharmaceutical Samples

A solid graphite-polyurethane composite electrode has been used to determine release profiles of verapamil, a calcium-channel blocker. The electro-oxidation process was characterized by cyclic voltammetry and electrochemical impedance spectroscopy and showed no adsorption of analyte or oxidation products, unlike at other carbon-based electrodes. Quantification gave linear ranges up to 40molL-1 with cyclic voltammetry and detection limits of 0.7molL-1 by differential pulse and square-wave voltammetry. Commercial product samples were successfully analyzed with results equal to those from spectrophotometry. Because no electrode surface renewal is needed, this electrode material has many advantages.

Epoxy Composite with Milimetric Carbon Nanotubes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Correlative light-electron fractography of interlaminar fracture in a carbon-epoxy composite

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Determination of Tetracycline in Environmental Water Samples at a Graphite-Polyurethane Composite Electrode

A bare graphite-polyurethane composite was evaluated in the tetracycline (TC) determination in natural water samples. Using differential pulse voltammetry (DPV), a linear response was observed in the range of 4.00-40.0 mu mol L-1 with limit of detection of 2.80 mu mol L-1, without the need of surface renewing between successive runs. During the tetracycline determination in water samples, recoveries between 92.6 and 100% were found. The results for TC determination in water samples after a pre-concentration stage agreed with spiked value at a 95% confidence level according to student t-test.

Determination of tetracycline in environmental water samples at a graphite-polyurethane composite electrode

A bare graphite-polyurethane composite was evaluated in the tetracycline (TC) determination in natural water samples. Using differential pulse voltammetry (DPV), a linear response was observed in the range of 4.00-40.0 µmol L-1 with limit of detection of 2.80 µmol L-1, without the need of surface renewing between successive runs. During the tetracycline determination in water samples, recoveries between 92.6 and 100% were found. The results for TC determination in water samples after a pre-concentration stage agreed with spiked value at a 95% confidence level according to student t-test.

Development of graphite epoxy housing for nickel-cadmium cell /

"Presented to Society for the Advancement of Material & Processing Engineering at 9th National Technical Conference, October 4-6, 1977, Atlanta, Georgia."

Double-Tagging Polymerase Chain Reaction with a Thiolated Primer and Electrochemical Genosensing based on Gold Nanocomposite Sensor for Food Safety

A novel material for electrochemical biosensing based on rigid conducting gold nanocomposite (nano-AuGEC) is presented. Islands of chemisorbing material (gold nanoparticles) surrounded by nonreactive, rigid, and conducting graphite epoxy composite are thus achieved to avoid the stringent control of surface coverage parameters required during immobilization of thiolated oligos in continuous gold surfaces. The spatial resolution of the immobilized thiolated DNA was easily controlled by merely varying the percentage of gold nanoparticles in the composition of the composite. As low as 9 fmol (60 pM) of synthetic DNA were detected in hybridization experiments when using a thiolated probe. Moreover, for the first time a double tagging PCR strategy was performed with a thiolated primer for the detection of Salmonella sp., one of the most important foodborne pathogens affecting food safety. Ibis assay was performed by double-labeling the amplicon during the PCR with a -DIG and -SH set of labeled primers. The thiolated end allows the immobilization of the amplicon on the nano-AuGEC electrode, while digoxigenin allows the electrochemical detection with the antiDIG-HRP reporter in the femtomole range. Rigid conducting gold nanocomposite represents a good material for the improved and oriented immobilization of biomolecules with excellent transducing properties for the construction of a wide range of electrochemical biosensors such as immunosensors, genosensors, and enzymosensors.

Magneto Immunoassays for Plasmodium falciparum Histidine-Rich Protein 2 Related to Malaria based on Magnetic Nanoparticles

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)