The use of a phenylpyrazine liquid crystalline material with a liquid crystalline solvent mediator as an ion-selective electrode

Liquid crystalline 2-n-hexyloxy-5-(4-bromophenyl)-pyrazine was investigated as a novel neutral ionophore for use in ion selective electrodes. Two memb rane compositions were studied. The first membrane included o-nitrophenyl o ctyl ether as a plasticising solvent mediator, and in the second membrane t he plasticising mediator was replaced with a commercial non-ionophoric liqu id crystal material (E7 Merck). The inclusion of E7, which exhibits solvent mediator properties, ensured the ionophore was present in a room temperatu re liquid crystalline phase. For membranes containing the E7, improved Nern stian response was observed for ammonium ions over the same concentration r ange, together with improved selectivity when used as ammonium and caesium selective electrodes. This is believed to be the first calamitic liquid cry stalline ionophore polymer system described and may have potential in direc t manipulation of ionophores in polymer membrane electrodes, using establis hed liquid crystal switching technology.