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

Comparison of the voltammetric behavior of metronidazole at a DNA-modified glassy carbon electrode, a mercury thin film electrode and a glassy carbon electrode

The electroanalytical performance at three electrodes: DNA-modified galssy carbon electrode, mercury thin film electrode and glassy carbon electrode, for the study of the electrochemical reduction of metronidazole is compared. All three electrodes showed a similar trend in the reduction mechanism for metronidazole, depenent on pH in the acid and neutral region and independent in alkaline media, although there was a shift in the peak potentials to more negative values when a bare glassy carbon electrode was used compared to the other two. Besides the advantage of using a solid electrode for the reduction of metronidazole, the DNA-modified galssy carbon electrode enables a lower detection limit of 1.0 muM owing to the preconecentration of the drug on the electrode surface, which is not the case for the mercury thin film or bare glassy carbon electrodes

Eduardo Neves, nosso eterno mestre

Eduardo Fausto de Almeida Neves, Professor Emeritus of the Universidade Federal de São Carlos and formerly Full Professor at the Instituto de Química - Universidade de São Paulo (USP), São Paulo, Brazil, was born in November 7, 1933 in Pedra Azul, MG, and deceased in July 2, 2006 in São Carlos, SP. He graduated under supervision of Professor Paschoal Senise, pioneer of Analytical Chemistry at USP, and developed his post-doctoral work at Caltech, USA, with Professor Fred Anson. His brilliant career as teacher, scientist, supervisor and mentor resulted in a prolific science school in Analytical Chemistry, with some sixty PhDs and masters supervised by him, amplified to over four hundred in the 2nd to 4th generations (still growing), spread throughout the country and nucleating new research groups. The contents of a hundred papers reflect Prof. Eduardo's wide range of scientific interests. Passionate inclination for creative intellectual activity, rooted in profound knowledge of all branches of Chemistry, broadminded thinking, sound experimentation, generous scientific cooperation and true friendship - that's why friends, colleagues and students referred to him as "master" or "my guru"

Effect of scavengers on the photocatalytic digestion of organic matter in water samples assisted by TiO2 in suspension for the voltammetric determination of heavy metals

The influence of electron and hole scavengers in the photocatalytic digestion of organic matter in the presence of suspended particles of TiO2 was investigated. The process, aiming at the electrochemical determination of traces of heavy metals in water samples, was followed through the recovery of the voltammetric wave of Cd(II) in the presence of EDTA, chosen as model ligand that mimics the complexing effect of natural dissolved organic matter. The accelerating power of O2, acting as electron scavenger, was confirmed. In the absence of O2, a similar function is played by nitrate ions but not, as it seems, by the analyte, Cd(II). On the other hand, CH3OH exhibits an antagonist effect as hole scavenger. This observation may explain why the acetate (from the pH buffer), used to control the medium acidity, leads to a certain reduction in the photocatalytic yield