Voltammetric Studies of Cu(II) Ion Transfer Reaction with Picolinamide-phenylenevinylene across Liquid/liquid Interfaces and Their Sensing Applications

Voltammetric responses associated with the transfer reaction of Cu(II) cations assisted by picolinamide-phenylenevinylene (picolinamide-PV) across a polarized liquid/liquid interface were investigated and their sensing applications were demonstrated. The transfer process characteristics of Cu(II) ions by picolinamide-PV at the water/1,2-dichloroethane (1,2-DCE) interface was first investigated using cyclic voltammetry. The assisted transfer behavior of Cu(II) ions was then compared to that of Cu(I) ions. In order for Cu(II) ion selective sensing applications, a single microhole interface featuring the water and polyvinylchloride-1,6-dichlorohexane (PVC-1,6-DCH) gel layer incorporating picolinamide-PV was fabricated. The sensitivity for Cu(II) ions was improved by the use of differential pulse stripping voltammetry, which preconcentrates Cu(II) ions in the gel layer by means of holding the transfer potential of Cu(II) ions at 800 mV (vs. Ag/AgCl) for 20 s followed by stripping the ions from the gel to the aqueous phase. The Cu(II) ion sensor exhibited a low detectable concentration of 1 μM (0.13 ppm) Cu(II) ions alongside a linear dynamic range of 1 μM (0.13 ppm) to 50 μM (6.72 ppm) Cu(II) cations. An excellent selectivity over Ni²⁺, Ba²⁺ and Ca²⁺ ions was also achieved.