Studies on Cation Selectivities of Some Pyridine-Based Ionophores for Use in Polymer Membrane Chemical Sensors

Abstract

The synthesis of some macrocyclic compounds based on 4-octyloxypyridine-2,6-dicarboxylic acid, containing sulfur and/or oxygen atoms in the 2 to 6-bridging unit, along with some non-cyclic analogues is reported. These were tested for cation selectivity in poly(vinyl chloride)-based membrane electrodes. Little selectivity was found for any ion with the oxygen-containing compounds, and none approached the selectivity for potassium reported previously for a related compound. High bonding affinities for class b acceptors, particularly Ag⁺ and Hg²⁺, were found for sulfur-containing compounds. The complexation with Hg²⁺ was so strong that the electrodes showed behaviour characteristic of an anion response.