Evaluation of some new 14- and 15-crown-formazans as carriers in cesium ion selective electrodes

A number of new crown-formazans with 14 and 15 membered rings have been inv estigated as selective neutral carriers in cesium ion selective electrodes. Two plasticizers (NPOE and NPBnE) were studied. The new 14-crown-formazan 4a containing the 4-pyridyl N-oxide at the formazyl carbon exhibited the hi ghest selectivity in cesium ion selective electrodes, especially towards th e two low selectivity monovalent ions K+ and NH4(+). Also, membranes contai ning the plasticizer NPBnE showed better cesium selectivity relative to mos t ions than those containing NPOE. Membranes containing 4a and variable com positions of plasticizers, potassium tetrakis-(p-chlorophenyl)borate (KTpCl PB), and trioctylphosphine oxide (TOPO) were studied in order to prepare an electrode with the optimum cesium selectivity. The highest selectivity for cesium was achieved with the two electrodes designated d and e with membra nes containing the ionophore 4a, NPBnE and KTpClPB with and without TOPO. S electivities are reported relative to sodium, potassium, barium, calcium, a mmonium, lithium, cobalt, and magnesium. (C) 1998 Elsevier Science B.V. All rights reserved.