A solid paraffin-based carbon paste electrode modified with 2-aminothiazole organofunctionalized silica for differential pulse adsorptive stripping analysis of nickel in ethanol fuel

A solid paraffin-based carbon paste electrode modified with 2-aminothiazole organofunctionalized silica (SiAt-SPCPE) was applied to Ni2+ determination in commercial ethanol fuel samples. The proposed method comprised four steps: (1) Ni2+ preconcentration at open circuit potential directly in the ethanol fuel sample, (2) transference of the electrode to an electrochemical cell containing DMG, (3) differential pulse voltammogram registering and (4) surface regeneration by polishing the electrode. The proposed method combines the high Ni2+ adsorption capacity presented by 2-aminothiazole organofunctionalized silica with the electrochemical properties of the Ni(DMG)2 complex, whose electrochemical reduction provides the analytical signal.All experimental parameters involved in the proposed method were optimized. Using a preconcentration time of 20 min, it was obtained a linear range from 7.5 x 10(-9) to 1.0 x 10(-6) mol L-1 with detection limit of 2.0 x 10(-9) mol L-1. Recovery values between 96.5 and 102.4% were obtained for commercial samples spiked with 1.0 mu mol L-1 Ni2+ and the developed electrode was totally stable in ethanolic solutions. The contents of Ni2+ found in the commercial samples using the proposed method were compared to those obtained by graphite furnace atomic absorption spectroscopy by using the F- and t-test. Neither the F- nor t-values exceeded the critical values at 95% confidence level, confirming that there are not statistical differences between the results obtained by both methods. These results indicate that the developed electrode can be successfully employed to reliable Ni2+ determination in commercial ethanol fuel samples without any sample pretreatment or dilution step. (c) 2006 Elsevier B.V. All rights reserved.

Copper determination in ethanol fuel by differential pulse anodic stripping voltammetry at a solid paraffin-based carbon paste electrode modified with 2-aminothiazole organofunctionalized silica

Solid paraffin-based carbon paste electrodes modified with 2-aminothiazole organofunctionalized silica have been applied to the anodic stripping determination of copper ions in ethanol fuel samples without any sample treatment. The proposed method comprised four steps: (1) copper ions preconcentration at open circuit potential directly in the ethanol fuel sample; (2) exchange of the solution and immediate cathodic reduction of the absorbate at controlled potential; (3) differential pulse anodic stripping voltammetry; (4) electrochemical surface regeneration by applying a positive potential in acid media. Factors affecting the preconcentration, reduction and stripping steps were investigated and the optimum conditions were employed to develop the analytical procedure. Using a preconcentration time of 20 min and reduction time of 120 s at -0.3 V versus Ag/AgCl(sat) a linear range from 7.5 x 10(-8) to 2.5 x 10(-6) mol L(-1) with detection limit of 3.1 x 10(-8) mol L(-1) was obtained. Interference studies have shown a decrease in the interference effect according to the sequence: Ni > Zn > Cd > Pb > Fe. However, the interference effects of these ions have not forbidden the application of the proposed method. Recovery values between 98.8 and 102.3% were obtained for synthetic samples spiked with known amounts of Cu(2+) and interfering metallic ions. The developed electrode was successfully applied to the determination of Cu(2+) in commercial ethanol fuel samples. The results were compared to those obtained by flame atomic absorption spectroscopy by using the F-test and t-test. Neither F-value nor t-value have exceeded the critical values at 95% confidence level, confirming that there are no significant differences between the results obtained by both methods. (c) 2006 Elsevier B.V. All rights reserved.

Electrochemical Behavior of a Glassy Carbon Electrode Chemically Modified with Nickel Pentacyanonitrosylferrate in Presence of Sulfur Compounds

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

Electrochemical and spectroscopic characterization of screen-printed gold-based electrodes modified with self-assembled monolayers and Tc85 protein

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

Electrochemical behavior of a glassy-carbon electrode chemically modified with cadmium pentacyanonitrosylferrate in the presence of tetrahydrothiophene

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

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.

Silver Nanocomposite Electrode Modified with Hexacyanoferrate. Preparation, Characterization and Electrochemical Behaviour Towards Substituted Anilines

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Determination of isoniazid in human urine using screen-printed carbon electrode modified with poly-L-histidine

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

Screen-Printed Carbon Electrode Modified with Poly-L-histidine Applied to Gold(III) Determination

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

Anodic Stripping Voltammetric Determination of Lead (II) and Cadmium (II) by Using a Carbon Nanotubes Paste Electrode Modified with Ion Exchange Synthetic Resin

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Use of a carbon paste electrode modified with spinel-type manganese oxide as a potentiometric sensor for lithium ions in flow injection analysis

A potentiometric sensor constructed from a mixture of 25% (m/m) spinel-type manganese oxide (lambda-MnO2), 50% (m/m) graphite powder and 25% (m/m) mineral oil is used for the determination of lithium ions in a flow injection analysis system. Experimental parameters, such as pH of the carrier solution, flow rate, injection sample volume, and selectivity for Li+ against other alkali and alkaline-earth ions and the response time of this sensor were investigated. The sensor response to lithium ions was linear in the concentration range 8.6 x 10(-5) - 1.0 x 10(-2) mol L-1 with a slope 78.9 +/- 0.3 mV dec(-1) over a wide pH range 7 - 10 (Tris buffer), without interference of other alkali and alkaline-earth metals. For a flow rate of 5.0 mL min(-1) and a injection sample volume of 408.6 muL, the relative standard deviation for repeated injections of a 5.0 x 10(-4) mol L-1 lithium ions was 0.3%.

Characterization of electrodes chemically modified with Mn(III) porphyrin/polypyrrole films as catalytic surfaces for an azo dye

In this study we describe the electrochemical behavior of 5,10,15,20-tetrakis(2'-aminophenylporphyrin)manganese(III) chloride supported on a glassy carbon electrode, as well as the electrochemical preparation and characterization of thin films based on pyrrole-3-carboxylic acid. The electrocatalytic action of the electrode modified with the Mn(III) porphyrin toward an azo dye was tested, and the characteristic strong interaction between the incorporated metalloporphyrin and RR120 dye was verified. Copyright (c) 2006 Society of Porphyrins & Phthalocyanines.

Voltammetric determination of persulfate anions using an electrode modified with a Prussian blue film

Prussian blue [PB, iron(III) hexacyanoferrate(II)] films are effective for the electrocatalysis of the persulfate (peroxodisulfate)/sulfate redox system. This has been exploited in the voltammetric determination of persulfate anions using a PB-modified platinum disc electrode. A linear correlation between electrocatalytic current and persulfate concentration was found for the range 5 x 10(-5) to 3 x 10(-3) mol dm(-3), using 0.100 mol dm(-3) potassium chloride as supporting electrolyte at pH 4. This analytical method has the advantages of speed and ease of operation in relation to traditional titrimetric methods for persulfate determination. The applicability of the method to the determination of persulfate in a commercial hair bleaching 'booster' product is demonstrated. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Amperometric differential determination of ascorbic acid in beverages and vitamin C tablets using a flow cell containing an array of gold microelectrodes modified with palladium

A simple and attractive method for quantification of ascorbic acid (AA) in beers, soda, natural juices and commercial vitamin C tablets was achieved by combining Bow injection analysis and amperometric detection. An array of gold microelectrodes electrochemically modified by deposition of palladium was employed as working electrode which was almost unaffected by fouling effects. Ascorbic acid was quantified in beverages and vitamin tablets using amperometric differential measurements. This method is based on three steps involving the flow injection of: 1) the sample plus a standard addition of AA, 2) the pure sample, and 3) the enzymatically-treated sample. The enzymatic treatment was carried out with Cucumis sativus tissue, which is a rich source of ascorbate oxidase, at pH 7. The calibration plots for freshly prepared ascorbic acid standards were very linear in the concentration range of 0.18-1.8 mg L-1 with a relative standard deviation (RSD) < 1%, while for real samples the deviations were between 2.7% to 8.9%.