Application of calixarene ionophores in PVC based ISEs for uranium detection

A lower rim functionalised calixarene molecule 5,11,17,23-tetra-tert-butyl- 25,27-bis(hydroxy)-26-(ethoxycarbonylmethoxy)-28-(diethyl carbamoyl-methoxy ) calix[4]arene, which was originally developed for solid phase extraction of trace uranium from environmental and industrial waste water, is tested a s a possible ionophore in ion selective electrodes (ISEs). PVC based membra nes containing the calix[4]arene were used in experiments to test the chara cteristics and viability of these sensors. The electrodes gave more stable potential readings when used around neutral pH 5.5-8.5. Extraction experime nts using the PVC membranes showed that the calix[4]arene complexed with:th e uranyl species end extracted it from the test solutions most effectively at around pH 7.0. The limit of detection for uranium species, around 1 ppm under normal conditions, was avoided by preconditioning the membranes at hi gh pH. The effect of testing for uranium selectivity amongst a matrix of ca tions and anions in a simulated waste solution showed that interference was significant. As we are at the beginning of this research, suggestions for further work on these electrodes are made in light of recent reports of wor k in this field. (C) 2001 Published by Elsevier Science B.V.