Flow injection analysis using carbon film resistor electrodes for amperometric determination of ambroxol

Flow injection analysis (FIA) using a carbon film sensor for amperometric detection was explored for ambroxol analysis in pharmaceutical formulations. The specially designed flow cell designed in the lab generated sharp and reproducible current peaks, with a wide linear dynamic range from 5 × 10-7 to 3.5 × 10-4 mol L-1, in 0.1 mol L-1 sulfuric acid electrolyte, as well as high sensitivity, 0.110 A mol-1 L cm-2 at the optimized flow rate. A detection limit of 7.6 × 10-8 mol L-1 and a sampling frequency of 50 determinations per hour were achieved, employing injected volumes of 100 [mu]L and a flow rate of 2.0 mL min-1. The repeatability, expressed as R.S.D. for successive and alternated injections of 6.0 × 10-6 and 6.0 × 10-5 mol L-1 ambroxol solutions, was 3.0 and 1.5%, respectively, without any noticeable memory effect between injections. The proposed method was applied to the analysis of ambroxol in pharmaceutical samples and the results obtained were compared with UV spectrophotometric and acid-base titrimetric methods. Good agreement between the results utilizing the three methods and the labeled values was achieved, corroborating the good performance of the proposed electrochemical methodology for ambroxol analysis.http://www.sciencedirect.com/science/article/B6THP-4RW434G-1/1/d40a3f00a2eaccb84817b064f601d0f

Determination of the surface charge density of a mercury electrode by extrusion: a new method for correction of the faradaic component

The accurate determination of the surface charge density at the mercury | solution interface by the method of extrusion of mercury drops is impaired by the faradaic current caused by traces of electroactive species. This paper describes a new design of a hanging mercury drop electrode with accurate control of the extruded electrode area, to within 0.1%, together with a new and reliable procedure for correction of the faradaic current. The procedure is based on first obtaining the correction parameters in the presence of increasing amounts of electroactive species and then using these parameters for correction of the faradaic component so as to obtain the surface charge density of the electrode. Implementation of the method with a microcomputer controlled system provides automatic acquisition of corrected electrode charge density values as a function of the electrode potential. The results obtained with this new method are in excellent agreement with those obtained by other methods, as illustrated for aqueous sodium fluoride solution.http://www.sciencedirect.com/science/article/B6TGB-3WS6M1X-4/1/959396100ce50f29fe3e81cc9a42242

An Electrochemically Synthesized Nanoporous Copper Microsensor for Highly Sensitive and Selective Determination of Glyphosate

A nanoporous copper (NPC) film was electrodeposited on a copper microelectrode, and the generated platform was investigated for electrochemical sensing of glyphosate (Glyp). The as-deposited NPC film was highly pure and crystalline according to results of energy dispersive spectroscopy and X-ray diffraction experiments, respectively. Scanning electron microscopy images confirm the NPC films possess a highly porous morphology containing dendrite fractals, and the electrodeposition parameters, particularly potential (Ed) and time (td), exert a remarkable influence on the structure of the films. Such changes in the NPC morphology with Ed and td were also correlated with the electrochemical behavior investigated by cyclic voltammetry. In the presence of Glyp, the anodic oxidation is facilitated because copper ions diffuse easily through the pores of the NPC film and form a complex with the analyte at the electrode interface. On the other hand, as the amount of copper oxides decreases due to the formation of soluble Cu(II) complex with Glyp, less current is obtained during the reverse scan, allowing a relationship between the decrease in the cathodic current and the Glyp concentration to be established. The optimized NPC-modified Cu microelectrode showed very high sensitivity (14 nA nmol−1 L), low detection limit (4 nmol L−1), excellent reproducibility, and selective response for Glyp. The applicability of the sensor was demonstrated by detecting Glyp in river water samples.Fil: Regiart, Daniel Matias Gaston. Universidade de Sao Paulo; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Kumar, Abhishek. Universidade de Sao Paulo; Brasil. Universite de Bourgogne; FranciaFil: Gonçalves, Josué M.. Universidade de Sao Paulo; BrasilFil: Silva Junior, Gilberto J.. Universidade de Sao Paulo; BrasilFil: Masini, Jorge César. Universidade de Sao Paulo; BrasilFil: Angnes, Lúcio. Universidade de Sao Paulo; BrasilFil: Bertotti, Mauro. Universidade de Sao Paulo; Brasi

Eletrodos fabricados por "silk-screen" Screen-printed electrodes

A review dealing with the use of screen-printing technology to manufacture disposable electrodes is presented, covering in details virtually all the publications in the area up to early 1997 and including 206 references. The elements and different strategies on constructing modified electrodes are highlighted. Commercial and Home-made ink recipes are discussed. Microelectrode arrays, built by the combination of photostructuring and screen-printing technologies to the mass production of advanced disposable sensors, are also discussed. Future research trends are predicted

Carbon film resistor electrode for amperometric determination of acetaminophen in pharmaceutical formulations

Flow injection analysis (FIA) with amperometric detection was employed for acetaminophen quantification in pharmaceutical formulations using a carbon film resistor electrode. This sensor exhibited sharp and reproducible current peaks for acetaminophen without chemical modification of its surface. A wide linear working range (8.0 × 10-7 to 5.0 × 10-4 mol L-1) in phosphate buffer solution as well as high sensitivity (0.143 A mol-1 L cm-2) and low submicromolar detection limit (1.36 × 10-7 mol L-1) were achieved. The repeatability (R.S.D. for 10 successive injections of 5.0 × 10-6 and 5.0 × 10-5 mol L-1 acetaminophen solutions) was 3.1 and 1.3%, respectively, without any memory effect between injections. The new procedure was applied to the analyses of commercial pharmaceutical products and the results were in good agreement with those obtained utilizing a spectrophotometric method. Consequently, this amperometric method has been shown to be very suitable for quality control analyses and other applications with similar requirements.http://www.sciencedirect.com/science/article/B6TGX-4MSHT96-1/1/a5eb87f817e43c4bd0120021afa851f

Biocatálise em meios aquo-restritos: fundamentos e aplicações em química analítica

The ability of enzymes to function in aquo-restricted media (commonly reported as non-aqueous media) has greatly enlarged the applications in numerous fields. The development of biosensors was also benefited with this area, expanding their applications toward many previously inaccessible analytes, enlarging significantly the scope of applications. In this review, some basic factors that influence biocatalytical reactions in aquo-restricted media is discussed. Attention is focused on the development, advantages and analytical applications of biosensors in non-aqueous media. Recent examples and relevant applications of their use are presented