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 diethyldithiocarbamate, Cu(dedtc)(2), have been undertaken in toluene containing Hex(4)NClO(4) or Hex(4)NPF(6) as electrolyte using conventional and micro-sized platinum disk electrodes; Interestingly, despite the insolubility of the charged products of electrolysis in dry toluene, the Cu(dedtc)(2) reversible arrow [Cu(dedtc)(2)](+) + e(-) and Cu(dedtc)2 + e(-) reversible arrow [Cu(dedtc)2]- processes are chemically reversible. The theoretically expected peak-type response is obtained in pure toluene under conditions of cyclic voltammetry using a 1-mm-diameter platinum 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 the supporting electrolyte concentration is at least 0.05 M. In the absence of added electrolyte, well-defined reduction and oxidation processes are obtained at microdisk electrodes with 30% (v/v) acetone or 20% (v/v) acetonitrile in toluene. However, in water-saturated toluene, adsorption or precipitation of [Cu(dedtc)(2)](+) occurs on the electrode surface, and this feature therefore leads to the development of a cathodic stripping method for the determination of copper which is not available 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 to provide a simple method for the sensitive determination of copper in aqueous media.