Influence of anionic additive on Hg2+ interference on Ag+-ISEs based on [2.2.2]p,p,p-cyclophane as neutral carrier

The influence of the anionic additive on the Hg2+ interference on Ag+-ion-selective electrodes (Ag+-ISEs) based on [2.2.2]p,p,p-cyclophane as pi-coordinating neutral carrier was studied by potentiometric measurements. The weakly coordinating carborane anion (7,8,9,10,11,12-hexabromocarborane, CB11H6Br6-) was compared with the commonly used tetrakis(4-chlorophenyl borate) (TpClPB(-)) as the anionic additive in plasticized PVC membrane-based Ag+-ISEs. The Hg2+ interference was reduced by six orders of magnitude when replacing TpClPB(-) with CB11H6Br6- as the anionic additive, resulting in log K-Ag,K-Hg = -3.8 +/- 0.1 determined by the matched potential method (MPM). This indicates that weakly coordinating carboranes may be particularly useful as anionic additives in ISEs for soft cations. (C) 2003 Elsevier B.V. All rights reserved.