Influence of the Nature of Trifluoroacetophenon Derivatives on Selectivity of Sulfate and Carbonate-Selective Electrodes

Abstract

UV-spectrophotometric and chromatographic studies of the distribution of trifluoroacetophenone (TFAF) and a number of its derivatives (heptyl ether of p-trifluoroacetylbenzoic acid (HE p-TFABA), p-methyltrifluoroacetophenone (p-MTFAF), 2,4-dimethyltrifluoroacetophenone (DMTFAF), 2,4,6-trimethyltrifluoroacetophenone (TMTFAF)) in a hexane-water system, which simplifies the modeling of a polyvinyl chloride membrane carbonate and sulfate-selective electrodes, were performed. These substances are used as neutral carriers (NC) in membranes of ion-selective electrodes, reversible to double-charged inorganic anions. A systematic study of the hydration of TFAF and a number of its derivatives was carried out. TFAF has increased solubility in water (the distribution coefficient D is 415) as compared to p-MTFAF, DMTFAF, TMTFAF and HE p-TFABA (D within 1360–2700), which does not allow to recommend it as an NC for making electrode membranes. The strongest hydration occurs for the HE p-TFABA in the alkaline medium. It has been found that p-MTFAF and HE p-TFABA form crystalline hydrates. The selectivity coefficients of carbonate and sulfate-selective electrodes were determined for all the NC studied and a number of them were made to improve the selectivity of the electrodes: TFAF k p-MTFAF k DMTFAF k TMTFAF k p-BTFAF (p-buthyltrifluoroacetophenone) k HE p-TFABA.