Ion-transfer voltammetry of heavy metal ions at liquid/liquid interface

Abstract

Voltammetric studies on the transfer of heavy metal ions at liquid/liquid interface facilitated by ionophore are discussed. In the presence of ionophore or organic extractant, such as 1, 4, 7, 10, 13, 16-hexathlacyclooctadecane and 5, 6-diphenyl-3-(2-pyridyl)-1, 2, 4-triazine, in organic phase, heavy metal ions, such as, Pb²⁺, Cd²⁺, Hg²⁺, Pd²⁺, and Zn²⁺ ions in aqueous phase give reversible or quasi-reversible voltammograms due to the ionophore-assisted ion-transfer across polarized organic/water interface. Thus, the ion-transfer voltammetry can be applied advantageously to the study of the equilibrium and dynamic properties of metal ion complexes in both organic and aqueous solutions. Ion-transfer stripping voltammetry, in which the ionophore-assisted anodic pre-concentration of analyte ions into a thin organic gel layer followed by catholic dissolution back to aqueous phase, can be applied to the trace determination of heavy metal ions at ppb level. The formal potentials of simple or non-assisted transfer of heavy metal ions, including Pb²⁺, Cd²⁺, and Zn²⁺ ions, at nitrobenzene/water interface are also discussed.