Voltammetric determination of trace mercury in chloride media at glassy carbon electrodes modified with polycationic ionomers.

The perfluorinated polycationic polymer Tosflex @ is used for preparing polymer modified electrodes able to preconcentrate and detect the anionic complex HgCl$-, which is the prevailing inorganic Hg(II) species in sea water and other chloride media. The study of the ion-exchange voltammetric behaviour of the tetrachloromercurate(I1) complex at Tosflex-modified electrodes indicates the efficient incorporation of the analyte into the polymeric coating to which a remarkable positive shift in the reduction potential of HgCli- to Hg” is associated. The partition and selectivity coefficient values for the ion-exchange equilibrium involved are calculated from voltammetric data. When using an ion-exchange preconcentration step under open circuit conditions followed by a cyclic voltammetry detection step, a detection limit in the 10m8 M range is achieved, the exact figure depending on the scan rate employed. The application of a reducing potential during the preconcentration (i.e., using a mixed ion-exchange + Faradaic preconcentration regime) and the use of differential pulse voltammetry, lower the relevant detection limit by about three orders of magnitude. Results concerning optimization of the experimental parameters as well as lowering of the influence of possible interferents, such as copper and competing anions, are reported. Finally, an analytical procedure for exploiting the peculiar properties of Tosflex-modified electrodes for the determination of mercury in coastal waters samples is proposed and experimentally tested

Electroanalytical study on the ion-exchange voltammetric behaviour of Hg(II) at tosflex-coated glassy carbon electrodes

The cyclic voltammetric behaviour of HgC! 2- at glassy carbon electrodes coated with a thin film of Tosflex ® IE-SA 48 (a perfluorinated anion exchanger) is studied. Concerning the reduction of HgCl24 - preconcentrated in the coating, a relevant positive shift in reduction peak potentials is observed, both when increasing the HgCI 2- solution concentration and decreasing the scan rate. The analysis of the voitammograms indicates that an irreversible reduction process is occurring. A remarkable positive shift in peak potentials with respect to bare electrodes is also observed. All experimental evidence obtained agrees with the formation of a metal phase, namely Hg °, whose deposition is highly favoured by the presence of the coating, as a consequence both of preconcentration effects and of the decrease in diffusion coefficients related to the ion-exchange incorporation. As far as the reoxidation of deposited Hg ° is concerned, the study of the effect of the scan rate, the anaiyte solution concentration and the loading of chloride anions in the coating indicates that the reversible oxidation to an insoluble calomel deposit occurs at high Hg ° and low CI- loadings. The formation of calomel is confned also by ex situ X-ray diffractometric measurements. On the contrary, low Hg and high CI- loadings within the coating favour the dispmportionation of the calomel formed and the complete regeneration of the modified electrode

Electrochemical Reduction of Triphenyltin Chloride in Aprotic Medium

The electrode mechanism for the reduction of theSnPh3Cl organometallic species in aprotic solvent is define

Electrode Processes of Oxygenated Nitrogen Compounds in Acetonitrile Medium. Part II. Nitrite Ion

The electrochemical behaviour of nitrite ions in acetonitrile medium has been investigated at platinum electrodes. The nitrite ion undergoes three consecutive oxidation steps with the formation of NO and NO3−, of N2O4 and of NO2+ respectively

Aragonite in Roman wall paintings of the VIII Regio, Aemilia and X Regio, Venetia et Histria

Aragonite was found in white stripes painted on mural paintings of the Roman period. This is so in VIII and X Regio of Ital