Determination of Analgesics (Dipyrone and Acetaminophen) in Pharmaceutical Preparations by Cyclic Voltammetry at a Copper(II) Hexacyanoferrate(III) Modified Carbon Paste Electrode

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Carbon fiber microelectrodes for adsorptive stripping analysis of trace nucleic acids

Carbon fiber ultramicroelectrodes are shown to be suitable for adsorptive stripping potentiometric measurements of trace DNA and RNA. The origin of the carbon fiber has a profound effect upon its suitability for trace analysis of nucleic acids, with the 'Aesar' materials performing most favorably. The resulting ultramicroelectrodes offer effective adsorptive accumulation of DNA and RNA from unstirred microliter-volume solutions, and are shown to be useful in adsorptive stripping transfer experiments. The influence of the surface pretreatment and accumulation conditions is described, along with the analytical-performance characteristics. The detection limits are 6, 15 and 40 mu g/l tRNA, ssDNA and dsDNA, respectively (5 min accumulation). (C) 1998 Elsevier B.V. S.A.

Caffeine Determination at a Carbon Fiber Ultramicroelectrodes by Fast-Scan Cyclic Voltammetry

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

Determination of N-Acetylcysteine by Cyclic Voltammetry Using Modified Carbon Paste Electrode with Copper Nitroprusside Adsorbed on the 3-Aminopropylsilica

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

Determination of 5-aminosalicylic acid in pharmaceutical formulations by square wave voltammetry at pencil graphite electrodes

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

Poly(glutamic acid) nanofibre modified glassy carbon electrode: Characterization by atomic force microscopy, voltammetry and electrochemical impedance

Glassy carbon electrodes (GCE) were modified with poly(glutamic acid) acid films prepared using three different procedures: glutamic acid monomer electropolymerization (MONO), evaporation of poly(glutamic acid) (PAG) and evaporation of a mixture of poly(glutamic acid)/glutaraldehyde (PAG/GLU). All three films showed good adherence to the electrode surface. The performance of the modified GCE was investigated by cyclic voltammetry and differential pulse voltammetry, and the films were characterized by atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). The three poly(glutamic acid) modified GCEs were tested using the electrochemical oxidation of ascorbic acid and a decrease of the overpotential and the improvement of the oxidation peak current was observed. The PAG modified electrode surfaces gave the best results. AFM morphological images showed a polymeric network film formed by well-defined nanofibres that may undergo extensive swelling in solution, allowing an easier electron transfer and higher oxidation peaks. (C) 2007 Elsevier Ltd. All rights reserved.

Determination of phosphorus in biodiesel using 1:12 phosphomolybdic modified electrode by cyclic voltammetry

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Electrooxidation of sulfide by cobalt pentacyanonitrosylferrate film on glassy carbon electrode by cyclic voltammetry

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)

Determination of sulfur compounds in gasoline using mercury film electrode by square wave voltammetry

A sensitive method based on square wave voltammetry is described for the quantitative determination of elemental sulfur, disulfide and mercaptan in gasoline using a mercury film electrode. These sulfur compounds can be quantified by direct dissolution of gasoline in a supporting electrolyte followed by subsequent voltammetric measurement. The supporting electrolyte is 1.4 mol L-1 sodium acetate and No acetic acid in methanol. Chemical and optimum operational conditions for the formation of the mercury film were analyzed in this study. The values obtained were a 4.3 mu m thickness for the mercury film, a 1000 rpm rotation frequency, -0.9 V applied potential and 600 s depositing time. Voltammetric measurements were obtained using square wave voltammetry with detection limits of the 3.0 x 10(-9), 1.6 x 10(-7) and 4.9 x 10(-7) mol L-1 for elemental sulfur, disulfide and mercaptan, respectively. (C) 2007 Elsevier Ltd. All rights reserved.

Determinação de zinco em álcool combustível opr voltametria de redissolução anódica

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

Cathodic stripping voltammetric determination of ceftazidime in urine at a hanging mercury drop electrode

A method was developed for the differential-pulse cathodic stripping voltammetric determination of ceftazidime with a hanging mercury drop electrode using its reduction peak at -0.43 V in Britton-Robinson buffer pH 4.0. The optimum accumulation potential and time were -0.15 V and up to 60 s, respectively. Linear calibration graphs were obtained from 1 x 10(-8) M and 1.5 x 10(-7) M. The limit of determination was calculated to be 5 x 10(-9) M. The coefficient of variation was 4% (n = 7) at 1 x 10(-7) M ceftazidime. The effect of various components of urine on the voltammetric response was studied, and creatinine, uric acid, urea, and glucose were shown to interfere in the method. Ceftazidime bound to human albumin gives a unique stripping peak at -0.48 V. Recoveries of 87% +/- 2% of the ceftazidime (n = 5) were obtained from urine spiked with 1.27 mu g ml(-1) using C-18 solid phase extraction cartridges. (C) 1997 Academic Press.

DEVELOPMENT OF A CHEMICALLY MODIFIED ELECTRODE BASED ON CARBON PASTE AND FUNCTIONALIZED SILICA-GEL FOR PRECONCENTRATION AND VOLTAMMETRIC DETERMINATION OF MERCURY(II)

A mercury-sensitive chemically modified electrode (CME) based on modified silica gel-containing carbon paste was developed. The functional group attached to the silica gel surface was 3-(2-thiobenzimidazolyl)propyl, which is able to complex mercury ions. This electrode was applied to the determination of mercury(II) ions in aqueous solution. The mercury was chemically preconcentrated on the CME prior to voltammetric determination by anodic stripping in the differential-pulse mode. A calibration graph covering the concentration range from 0.08 to 2 mg l-1 was constructed. The precision for six determinations of 0.122 and 0.312 mg l-1 Hg(II) was 3.2 and 2.9% (relative standard deviation), respectively. The detection limit for a 5-min preconcentration period was 0.013 mg l-1. A study for foreign ions was also made.

Anodic stripping voltammetric determination of aurothiomalate in urine using a screen-printed carbon electrode

This work describes an electroanalytical method for determining gold(I) thiomalate, aurothiomalate, widely used for treatment of reumatoid arthiritis, using a screen-printed carbon electrode (SPCE). Aurothiomalate (AuTM) was determined indirectly at the same electrode by accumulating it first at -1.5 V vs. printed carbon. At this potential in the adsorbed state, the AuTM is reduced to Au(0), which is then oxidized at two steps at -0.22 V and +0.54 V on SPCE. Using optimized conditions of 60 s deposition time, -1.5 V (vs. printed carbon) accumulation potential, 100 mV s(-1) scan rate, linear calibration graphs can be obtained by monitoring the peak at +0.54 V for AuTM in HCl 0.1 mol L-1 from 1.43 x 10(-6) to 1.55 x 10(-4) mol L-1. A limit of detection obtained was 6.50 x 10(-7) mol L-1, and the relative standard deviation from five measurements of 3.0 x 10(-5) mol L-1 AuTM is 4.5%. The method was successfully applied for AuTM determination in human urine sample.

Analytical procedure for total mercury determination in fishes and shrimps by chronopotentiometric stripping analysis at gold film electrodes after microwave digestion

A method for the total mercury determination in fish and shrimps employing chronopotentiometric stripping analysis on gold film electrodes is described. Fish and shrimp tissues were digested using a microwave oven equipped with closed vessels. We developed a microwave heating program which decomposed all the samples employing diluted nitric acid and hydrogen peroxide. The proposed method was validated by analyzing a certified reference material and then applied for different fish species from fresh water and seawater acquired in local markets of São Paulo city, Brazil. The Brazilian legislation establishes 0.5 and 1 mg per kilogram of fish as upper limit of mercury for omnivorous and predator species, respectively. Except for blue shark tissues, the mercury content was situated below 0.5 mu g g(-1) for all the analyzed samples. The detection limit of the proposed method was calculated as 5 ng g(-1) of sample utilizing 5 minutes of electrodeposition (+300 mV vs. Ag/AgCl) on the gold electrode. (c) 2006 Elsevier Ltd. All rights reserved.