Determination of Uranyl Ions Using Poly(vinyl chloride) Based 4-tert-Butylcalix[6]arene Membrane Sensor

Abstract

Membranes of 4-tert-butylcalix[6]arene I as an ion active material in poly(vinyl chloride) (PVC) based matrix have been tried for uranyl-selective sensors. The effect of anion excluder, sodium tetraphenylborate (NaTPB) and plasticizers, tris(2-ethylhexyl)phosphate (TEP), tributyl phosphate (TBP), dibutyl phthalate (DBP), 1-chloronaphthalene (CN) and diphenyl ether (DPE) on the performance of the membrane electrodes has also been studied. It was observed that the membrane having the composition I: PVC:NaTPB:TBP in the ratio 7:52:6:35 gave the best results with a wide working concentration range of3.9× 10–5–1.0–× 10–1 M, Nernstian slope of 29.1 mV per decade of activity, fast response time of 10 s and moderate selectivity over a number of mono-, bi- and trivalent cations. The sensor works well in the pH range 2.2–3.2 and can be successfully employed for the estimation ofUO22 +in partially nonaqueous medium having upto 20% (v/v) nonaqueous content. The sensor was used for the estimation of uranium as uranyl ions in simulated mixtures where the results are comparable to those obtained from radiochemical methods.