Abstract: Carbon paste electrodes (CPEs) modified with different soils in their native form were prepared to create a soil-like solid phase suitable fur application in studies of heavy metal ion uptake and binding interactions. The preparation of CPEs modified with five different soils was examined and their heavy metal ion uptake behavior investigated using a model Cu(II) aqueous solution. Metal ions were accumulated under open circuit conditions and were determined after a medium exchange using differential pulse anodic stripping voltammetry, applying pre-electrolysis at -0.7 V. The soil-modified CPE accumulation behavior, including the linearity of the current response versus Cu(II) concentration, the influence of the pH on the solution, and the uptake kinetics, was thoroughly investigated. The correlation between the soil-modified CPE uptake capability and the standard soil parameters, such as ion exchange capacity, soil pH, organic matter and clay content, were evaluated for all five examined soils. The influence of selected endogenous cations (K(I), Ca(II), Fe(III)) on the transfer of Cu(II) ions from a solution to the simulated soil solid phase was examined and is discussed. Preliminary examinations of the soil-modified CPE uptake behavior with some exogenous heavy metal ions of strong environmental interest (Pb(II), Ng(II), Cd(II) and Ag(I)) are also presented. This work demonstrates some attractive possibilities fur the application of a soil-modified CPE in studying soil-heavy metal ion binding interactions, with a further potential use as a new environmental sensor appropriate fur fast on-site testing of polluted soils.

Abstract: Voltammetric measurements were performed using a static Hg drop electrode, a Ag/AgCl/KCl (saturated) reference electrode and Pt-wire counter electrode. Cyclic voltammograms of bromofenoxim (I) in Britton-Robinson (BR) buffer of pH 7 were obtained at 200 mV/s. Two well defined reductive peaks were observed at -0.38 and -0.54 V. The peak at -0.38 V was used for subsequent measurements of I. For analysis by square-wave voltammetry, the calibration graph was linear for 0.0011-1.3 µM-I and the detection limit was 0.1 µg/l. The in situ formation and dynamic properties of Hg film-coated glassy C electrodes for the determination of I by FIA were investigated; 0.5 M KNO3/20 mM BR buffer of pH 7 was used as carrier and amperometric detection was at -0.7 V vs. Ag/AgCl. The response was linear for 0.11-9 µM-I with a detection limit of 10 µg/l. The RSD (n = 25) was 3.2%.

Abstract: The cited electrode was fabricated by dipping a glass substrate precoated with a thin layer of indium tin oxide into a sol gel prepared from CeCl3.7H2O and titanium isopropoxide. The electrode was air-dried then heated at 300°C for 10 min. The resulting CeO2/TiO2 thin-film electrode was used as an amperometric sensor in a flow injection system for monitoring electroinactive monovalent cations, viz., Li, Na, K, ammonium and tetraethylammonium ions. Typically, the sample (50 µL) was injected into an aqueous carrier stream at a flow rate of 1 ml/min and the analyte cation was detected at the thin-film electrode at -0.9 V vs. Ag/AgCl. The calibration graph was linear from 0.4-4 mM Li; the detection limit was 0.02 mM. RSD was 5.7% (n = 8) at the 1 mM level. Similar calibration data were obtained for the other cations studied. The results obtained were comparable to those obtained by conductimetric detection.