Fiber-optic cation determination using crown ether dyes immobilized on polymer membranes

This study describes the determination and comparison of some cations such as Na+, K+, Ba2+ and Cu2+ in aqueous media by using crown ether dyes immobi lized onto thin (0.04 mm) sulfonated kraton polymeric membranes. The studie s have been carried out in aqueous solutions first, and in dye-immobilized membrane systems later. The flow-cell system has been found to be more prac tical in application and had lower response times (30-60 s) as well as dete ction limits (2.24 x 10(-10)-1.19 x 10(-8) mol l(-1)). The optimum pH range for the formation of ion-dye complexes have been found to be 5 and 9 for t he ions above. Since the complexation reactions were reversible it was poss ible to regenerate the membranes by using HCl solutions and reuse them many times. The same membrane showed high reproducibility and low relative stan dard deviation. In addition, the interferences of the studied cations to ea ch other and of other various cations during the determinations have also b een investigated. (C) 1998 Elsevier Science S.A. All rights reserved.