RESPONSE MECHANISM OF ANION-SELECTIVE ELECTRODES BASED ON MERCURY ORGANIC-COMPOUNDS AS IONOPHORES

New mercury organic compounds with 1-3 metal centers and different sub stituents were synthesized as anion-selective ionophores. They were in corporated into solvent polymeric membranes, and the selectivity, slop e of response, response time, emf repeatability, and the signal stabil ity of the corresponding ion-selective electrodes (ISEs) were studied. Ortho-dimercury aromatic compounds were found to induce an adequate c hloride-selectivity for Physiological measurements. The anion complexa tion behavior of the ionophores in organic phases was investigated by C-13-NMR-monitored titrations with different tridodecylmethylammonium salts. Generally, the mercury organic compounds were shown to act as e lectrically neutral ionophores, forming negatively charged complexes w ith anions (one anion bound per mercury atom). A preference of chlorid e and thiocyanate over nitrate and perchlorate was documented. In two- phase experiments with IR and Hg-199-NMR detection, the chemical stabi lity of the ionophores during exposure to different aqueous electrolyt es was investigated. Compounds with native acetoxy or trifluoroacetoxy substituents at the mercury centers showed a limited stability in con tact with chloride solutions. Structural changes of the ionophores due to an exchange of substituents were observed, which were responsible for potential instabilities of the respective ISEs. The mercury organi c compound ETH 9033 with chloro-substituents was most stable, and ISEs based on it showed the best performance.