Differential pulse anodic stripping voltammetric determination of traces of copper with a tobramycin-Nafion modified electrode.
A Nafion-modified glassy carbon electrode incorporated with tobramycin for the voltammetric stripping determination of Cu2+ has been explored. The electrode was fabricated by tobramycin containing Nafion on the glassy carbon electrode surface. The modified electrode exhibited a significantly increased sensitivity and selectivity for Cu2+ compared with a bare glassy carbon electrode and the Nafion modified electrode. Cu2+ was accumulated in HAc-NaAc buffer (pH 4.6) at a potential of -0.6 V (vs. SCE) for 300 s and then determined by differential pulse anodic stripping voltammetry. The effects of various parameters, such as the mass of Nafion, the concentration of tobramycin, the pH of the medium, the accumulation potential, the accumulation time and the scan rate, were investigated. Under the optimum conditions, a linear calibration graph was obtained in the concentration range of 1.0 x 10(-9) to 5.0 x 10(-7) mol l(-1) with a correlation coefficient of 0.9971. The relative standard deviations for eight successive determinations were 4.3 and 2.9% for 1.0 x 10(-8) and 2.0 x 10(-7) mol l(-1) Cu2+, respectively. The detection limit (three times signal to noise) was 5.0 x 10(-10) mol l(-1). A study of interfering substances was also performed, and the method was applied to the direct determination of copper in water samples, and also in analytical reagent-grade salts with satisfactory results.
VOLTAMMETRIC DETECTION OF TRACES OF COPPER USING A CARBON PASTE ELECTRODE MODIFIED WITH TETRAPHENYLPORPHYRIN
ABSTRACT The voltammetric detection of copper(II) was carried out at a carbon paste electrode (CPE) modified with tetraphenylporphyrin (TPP). The analysis procedure consisted of an open circuit preconcentration step in stirred sample solution. This was followed by medium exchange to a pure electrolyte solution (Britton-Robinson buffer pH = 6) where the accumulated copper(II) was reduced at −0.8 V vs. Hg/Hg2SO4 and subsequently an anodic potential scan was effect to obtain the voltammetric peak. The parameters and conditions such as pH of the analyte solution and supporting electrolyte, preconcentration time, CPE composition, its activation and regeneration, and others, were studied in detail. The detection limit of the proposed procedure was found to be 2.0 × 10−9 mol l−1 of Cu(II) in the analyte solution for a preconcentration time of 12 min. Applying suitable preconcentration times, a linear calibration graph from 9.0 × 10−8 to 5.0 × 10−5 mol l−1 of Cu(II) was established. Multiple determinations (n = 8), following a preconcentration–measurement–regeneration cycle, gave a relative standard deviation of 4.5% at Cu(II) concentration of 1.0 × 10−7 mol l−1. The proposed method was applied to the determination of Cu(II) in a real sample of residue solution after extraction and a mineral sample of Jinchuan Corporation.
Electroanalysis with chemically modified electrodes
Modification des electrodes par depots de films de copolymeres (polyvinylpyridine/vinylferrocene et polyvinylbipyridine/vinylferrocene) qui comprennent un centre electroactif et un site de coordination, ce qui permet des electroanalyses d'ions metalliques avec une bonne sensibilite et selectivite