CESIUM ION-SELECTIVE ELECTRODES BASED ON CROWNED BENZOQUINONES

Three new derivatives of benzo-15-crown-5 were examined as potential c aesium ion-selective ionophores in PVC membrane electrodes. The ionoph ores were 2,3-benzoquino[15]crown-5, 2-bromo-1,4-dihydroxybenzo[15]cro wn-5 and 5-bromo2,3-benzoquino[15]crown-5. PVC membranes plasticized w ith 2-nitrophenyl octyl ether, and incorporating the secondary ion exc hanger potassium tetrakis(4-chlorophenyl)borate mere used throughout t his study, Interferent studies for each electrode were carried out to assess electrode selectivity in the presence of ammonium ion, alkali a nd alkaline earth ions and selected transition metals, A graphical met hod of representing selectivity coefficients is provided together with the separate solution technique for selectivity determination. Dynami c response, precision, lifetime and temperature studies was also repor ted, The benzoquinone crown ethers proved to be good caesium ionophore s, displaying near-Nernstian responses to this ion, in the range 10(-1 )-10(-4.5) mol I-1. The electrode incorporating the 2,3-benzoquino[15] crown-5 ionophore had the highest selectivity for caesium ions over al kali and alkaline earths studied.