Response and Selectivity Characteristics of Alkylammonium Ion-Selective Electrodes.

摘要

A series of polyvinyl chloride matrix coated-wire electrodes (c.w.e) based on dinonylnaphthalene sulfonic acid (DNNS) selective to various aklylammonium ions was prepared and selectivity characteristics were evaluated. Using a set of tributylammonium c.w.e., the interference by homologous series of alkylammonium ions were studied. It was found that selectivity coefficient values for alkyammonium ions at a given carbon number decrease in order primary, secondary, tertiary, quaternary. A linear increase in log selectivity coefficient with carbon number was observed in each series. Two additional sets of electrodes selective to dodecylammonium ion and to di-n-hexylammonium ion were evaluated for response to other C-12 amines. It was observed that electrodes for primary amines show little or no response to secondary and tertiary amines, while electrodes for tertiary amines respond strongly to primary amines and less strongly to secondary amines. The effect of structural modifications was evaluated in a study of N-substituted cyclohexylamines. The dependence of the magnitude of selectivity coefficient on interferent concentration was determined for both strong and weak interfering species. For strong interferences, selectivity coefficient was observed to increase to a maximum value of characteristic concentration. For weak interferents, the selectivity coefficient variation with interferent concentration was markedly less. Guides for estimating the response to an interfering species based on its structure and molecular weight were obtained from these studies.