Search

Successful applications of different analytical procedures to determine quantitatively mercury in aqueous media can be found in recent literature. Fundamentally it has made use of Cold Vapour Atomic Absorption Spectrometry (CV-AAS), X-Ray Fluorescence or UV Spectrophotometry, Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), or Inductively Coupled Plasma Mass Spectrometry (ICP-MS), which are the techniques commonly used for trace measurement of heavy metal in the laboratory. In this paper a new and alternative methodology to determine quantitatively mercury in aqueous media is reported. A kryptofix carbon-paste electrode has been used to determine voltammetrically mercury. The detection limit for mercury was evaluated to be 0.12 µg/l. [ABSTRACT FROM AUTHOR]

A film of polypyrrole/γcyclodextrin (PPY/γCD) was synthesized at a gold electrode by the simple electropolymerization of a 1:1 mixture of γCD and pyrrole monomer in aqueous solutions. Different voltammetric behaviors were obtained between PPY/γCD and PPY during the electrosynthesis process. Electrochemical impedance spectroscopy (EIS) was used to characterize the electrical properties of the electropolymerized films. The PPY/γCD films exhibit interesting properties such as a wider potential range for electroanalytical exploration that yields to easier and improved electrochemical detection of neurotransmitters such as dopamine, L-dopa, epinephrine, norepinephrine, and isoproterenol. Well resolved and reversible cyclic voltammograms (CVs) of these organic compounds could be obtained easily at the modified electrode with a negative shift of their oxidation potentials as compared with the response at bare gold electrodes. The plot of the neurotransmitters' catalytic currents vs. their concentrations gave good linear relationship inside the range of 2·10-6–2·10-5 M with R2 = 0.998. Detection limits between 6·10-7 M and 6·10-6 M were obtained for the molecules studied. According to the CV' s scan rate evolution, the electron transfer for the neurotransmitters was mainly diffusion controlled at the polymer-γCD/solution interface. Attempts to use the PPY/γCD sensor on real human serum for L-dopa exploration yield encouraging data. [ABSTRACT FROM AUTHOR]

A simple approach for increasing the sensitivity and selectivity for the detection of mercury(II) species in water is presented. The technique is based on two steps: (1) micro-extraction (uptake step) of mercury(II) by simply incubating an electropolymerized poly(3-methylthiophene) (P3MT) modified gold electrode, at open-circuit potential conditions, into a solution containing the heavy metal for 30 min and (2) the electrode is transferred from the analyte solution to an electrochemical cell (release step) for successive voltammetric determinations. Surprisingly, cyclic voltammetric measurements showed a first large anodic peak characteristic of oxidation of metallic mercury to form mercury(II) at 0.53 V. The reversed scan, showed a smaller cathodic peak at 0.4 V, suggesting a possible electroless reduction from Hg(II) to metallic mercury during the extraction step probably caused by the heteroatom of P3MT. Under these conditions, differential pulse voltammetry (DPV) measurements performed on the P3MT electrode showed that the anodic peak current exhibit a good linear concentration dependence in the range 10−8–4 × 10−6 mol/L. The detection limit was estimated for S/N > 3 to be 10−10 mol/L. The analytical performances of the extraction method has been explored by optimizing the electropolymerization time, pH, and effect of interferences due to other ions. On the other hand, scanning election microscopy–energy dispersive analysis of x-ray (SEM–EDAX) and electrochemical impedance spectroscopy (EIS) measurements performed on P3MT films confirmed the adsorption of the heavy metal on the polymeric film due to the extraction process. [ABSTRACT FROM AUTHOR]