Trifluoroacetophenone derivative-based carbonate ion-selective electrodes: effect of diluent pH on the anion selectivity☆

Abstract Potentiometric properties of carbonate-selective electrodes were examined from both theoretical and experimental viewpoints, evaluating the relationship between dilution buffer pH and anion selectivity, and the effect of the type of buffer reagents (i.e. basic or acidic nature) on the carbonate measurement. The Nikolskii equation expressed in terms of the activity of hydroxide describes the potentiometric behavior of trifluoroacetophenone derivative (TFA)-based carbonate-selective electrodes well. Also investigated were the response characteristics of PVC-based carbonate-selective membranes doped with four different TFAs (e.g. trifluoroacetyl- p -decylbenzene (TFADB), 1,7-bis(4′-trifluoroacetophenyl)-4-dodecyl-1,7-dioxo-2,6-dioxy-heptane (compound I), 1,2-bis(4-trifluoroacetylbenzoyloxymethyl) benzene (compound II), and 2,7-diaza-1,8-bis(4′-trifluoroacetophenyl)-2,7-di(1′′-hexyl)-1,8-dioxo-octan (compound III)). Of these electrodes, the one based on compound III exhibited the best carbonate selectivity, response slope, and detection limit in a high pH (e.g. pH>9.0) dilution buffer.