Evaluation of a Ru-bipod Complex as a Redox Transducer for Membrane-Based Voltammetry of Anions

Abstract

Molecular redox compounds show promise for the development of solid contact ion selective electrodes (SC-ISEs) for anion determinations. In this work, a hydrophobic bis-tridentate Ru-bipod complex was studied as a molecular redox transducer in voltammetric SC-ISEs. Thin film voltammetric behavior was achieved in films comprised of the Ru-bipod complex, polyvinylchloride (PVC) and a plasticiser, nitrophenyloctylether (NPOE). Importantly, the choice of plasticiser had a significant effect on the SC-ISE response of the Ru-bipod complex; i. e., voltammetric responses of the Ru-bipod complex in NPOE films were sharper and more intense than in bis(2-ethylhexyl) sebacate (DOS) films. Moreover, addition of tetradodecylammonium tetrakis(4-chlorophenyl)borate (ETH 500) to the membrane had an unfavorable impact on detection of anions due to oxidation of this salt in the film. Although the thin film electrode showed close-to-Nernstian behavior in anion responses, the detection responses in the presence of very hydrophilic anions such as sulfate ion were shifted to higher potentials (>1 V) with a subsequent loss of sensitivity. Overall, the Ru-bipod complex operates as a simple transducer in SC-ISEs with benefits in anion detection.