VOLTAMMETRY OF COPPER DIETHYLDITHIOCARBAMATE IN TOLUENE AND TOLUENE-BASED SOLVENTS - DEVELOPMENT OF A SOLVENT EXTRACTION-STRIPPING METHOD FOR THE DETERMINATION OF COPPER USING MICRODISK ELECTRODES

Voltammetric studies of the oxidation and reduction of copper diethyld ithiocarbamate, Cu(dedtc)(2), have been undertaken in toluene containi ng Hex(4)NClO(4) or Hex(4)NPF(6) as electrolyte using conventional and micro-sized platinum disk electrodes; Interestingly, despite the inso lubility of the charged products of electrolysis in dry toluene, the C u(dedtc)(2) reversible arrow [Cu(dedtc)(2)](+) + e(-) and Cu(dedtc)2 e(-) reversible arrow [Cu(dedtc)2]- processes are chemically reversib le. The theoretically expected peak-type response is obtained in pure toluene under conditions of cyclic voltammetry using a 1-mm-diameter p latinum disk working electrode if the temperature is raised to 50 0 C and the supporting electrolyte concentration is about 1 M. At ambient temperatures, nearly ideal steady-state responses are obtianed for a 1 mM solution using a 1-mu m-diameter platinum microdisk electrode if t he supporting electrolyte concentration is at least 0.05 M. In the abs ence of added electrolyte, well-defined reduction and oxidation proces ses are obtained at microdisk electrodes with 30% (v/v) acetone or 20% (v/v) acetonitrile in toluene. However, in water-saturated toluene, a dsorption or precipitation of [Cu(dedtc)(2)](+) occurs on the electrod e surface, and this feature therefore leads to the development of a ca thodic stripping method for the determination of copper which is not a vailable in dry toluene. It therefore follows that solvent extraction of aqueous copper(II) into toluene as the Cu(dedtc)(2) complex can be coupled with cathodic stripping voltammetry at a microdisk electrode t o provide a simple method for the sensitive determination of copper in aqueous media.