Poly(vinyl) chloride membrane caesium-selective electrodes based on doubly crowned 1,3-calix[4]arenes

Two calix[4]arenebiscrown-6 derivatives in the 1,3-alternate conformation were tested as caesium-selective ionophores in poly(vinyl) chloride (PVC) membrane electrodes. The ionophores were 1,3-calix[4]biscrown-6 (BC6) and 1,3-calix[4]bisnaphthylcrown-6 (BC6N). PVC membranes plasticised with o-nitrophenyl octyl ether and without lipophilic salt additives were used throughout this study. These ligands produced electrodes with Nemstian behaviour. The selectivity coefficients for caesium with respect to alkali, alkaline earth, hydrogen and ammonium ions were determined. The effects of counteranions on the electrodes' performance were also studied. The electrodes' response demonstrated the ability of the ligands to act as neutral carriers independent of the presence of lipophilic salts in the membrane phase and Cl- or NO3- in the test solution. Better results than those previously reported with other ligands in terms of detection limit (3x10(-7) M) and Cs/Na selectivity (K-pot of 1.1x10(-5) and 7.4x10(-6) for BC6 and BC6N, respectively) were found for the doubly crowned 1,3-calixarenes. (C) 1998 Elsevier Science B.V. All rights reserved.