Anion-Selective Optical Sensors Based on a Coextraction of Anion-Proton Pairs into a Solvent-Polymeric Membrane

Abstract

The design of optical sensing devices for anions based on the coextraction of anions and protons into a PVC membrane is described. The extraction is controlled by the lipophilicity of the anions, while the coextracted protons in conjunction with a hydrogen ion selective chromoionophore provide the optical signal transduction. The absorbance of the membrane at a fixed pH of the aqueous sample solution and at constant anion concentrations is related to the hydration energy (Hofmeister series) of the anions. Calibration curves, response times, and reproducibilities of such sensor systems are presented. Membranes for optodes are at hand for an analytically relevant assay of lipophilic anions such as nitrate.