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.
A new electrochemical sensor for heavy-metal ions by the surface-polarization controlling method
A new electrochemical sensor with high sensitivity and selectivity for heavy-metal ions was proposed. The sensor was based on the electrochemical impedance spectroscopy (EIS) attributing to a constant phase element (CPE) behavior under dynamically controlled electrode potential. With the measurements of the CPE behavior by the surface-polarization controlling method, various heavy-metal ions could be easily detected and discriminated. No interference of counter anions such as Cl/sup -/, NO/sub 3//sup -/ and CH/sub 3/COO/sup $/was observed, and the same metal ions gave similar sensor response patterns regardless of the counter anions. Especially, the present method offers a high sensitivity of ppb levels for the most highly toxic elements, i.e., Hg/sup 2+/ and Hg/sup +/.
Do Potential People Have Moral Rights?
By a potential person I shall mean an entity which is not now a person but which is capable of developing into a person, given certain biologically and/or technologically possible conditions. This is admittedly a narrower sense than some would attach to the term ‘potential'. After all, people of the twenty-fifth century, if such there will be, are in some sense potential people now, even though the specific biological entities from which they will develop, i.e. the particular gametes or concepti, do not yet exist. For there do exist, in the reproductive capacities of people now living and in the earth's resources, conditions adequate to produce these future people eventually, provided of course that various possible catastrophes are avoided. Indeed, in some sense of ‘potential’ there have been countless billions of potential people from the beginning of time. But I am concerned not with such remote potentialities but with currently existing entities that are capable of developing into people.