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 π-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 KAg,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.