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.