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

Potentiometric properties of carbonate-selective electrodes were examined f rom both theoretical and experimental viewpoints, evaluating the relationsh ip 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 meas urement. The Nikolskii equation expressed in terms of the: activity of hydr oxide describes the potentiometric behavior of trifluoroacetophenone deriva tive (TFA)-based carbonate-selective electrodes well. Also investigated wer e the response characteristics of PVC-based carbonate-selective membranes d oped with four different TFAs (e.g. trifluoroacetyl-p -decylbenzene (TFADB) , 1,7-bis(4-trifluoroacetophenyl)-4-dodecyl-1,7-dioxo-2,6-dioxy-heptane (co mpound I), 1,2-bis(4-trifluoroacetylbenzoyloxymethyl) benzene (compound II) , and 2,7-diaza-1,8-bis(41-trifluoroacetophenyl)-2,7-di(1 "-hexyl)- 1,8-dio xo-octan (compound III)). Of these electrodes, the one based on compound II I exhibited the best carbonate selectivity, response slope, and detection l imit in a high pH (e.g. pH > 9.0) dilution buffer. (C) 1999 Elsevier Scienc e S.A. All rights reserved.