Studies of spectrophotometric reagents in some transition metal and lead ion-selective electrodes

Abstract

The general performance of ten spectrophotometric reagents, namely salicylaldoxime, 2,2′-dipyridyl, dimedone, 8-hydroxyquinoline, dithiooxamide, cupferron, nioxime, 4-methylnioxime, 1,10-phenanthroline hydrate and α-benzoin oxime, as active sensors for Cu²⁺, Co²⁺, Ni²⁺, Cd²⁺, Fe³⁺ and Pb²⁺ ions in a poly(vinyl chloride) membrane electrode system has been assessed using dioctyl phenyl phosphonate as plasticizing solvent mediator. Of the ten ionophores studied, four, namely salicylaldoxime, 2,2′-dipyridyl, dimedone and 8-hydroxyquinoline, showed good response to Pb²⁺ ions with the working concentration range from 1 × 10^–6 to 1 × 10^–1 mol dm^–3. The best response to Cu²⁺ ions was shown by electrodes based on 2,2′-dipyridyl, dithiooxamide and cupferron. Although the electrode with 8-hydroxyquinoline as the active sensor responded very well to Fe³⁺, the complex formed leached into solution. The most promising of the ionophores for the fabrication of Ni²⁺ ion-selective electrodes were found to be salicylaldoxime and cupferron with linear slopes of 32.9 and 22.5 mV per decade, respectively, from 1 × 10^–4 to 3.2 × 10^–2 mol dm^–3.