From an environment viewpoint, estimates of thallium-ion concentration have become a major interest because of their high toxicity. Ion- selective electrodes (ISE) are one of the most convenient and reliable analytical tools for estimating metal ion concentrations. There have been only a few reports concerning thalium(I) liquid membrane electrode [1-3]. In this study, we report the use of different crown ethers such as dibenzo-30-crown-10(DB30C10), dibenzo-21-crown-7(DB21C7), and dibenzyldiaza-18-crown-6(DBzDAC6) as sensor moleculs in construction of thalium(I)-PVC membrane electrodes. The conditioned electrode incorporated DBzDA18C6 gave best results with a wide working concentration range of 10-5- 10-1 M near - Nernstian slope of 56.9 mv/ decade of activity and detection limit of 5.6 × 10-6 M. This electrode exhibited a fast response time 10 s and high selectivity over Li+, K+, Cs+, NH4+ and other metal ions. The electrode works well in the pH range 4.0-11 and can be successfully employed for the determination of Tl+ ions. This proposed electrode was also used as an indicator electrode in determination of solubility product of some insoluble thalium(I) salts at 25 °C References [1] M.B. Saleh, J. Electroanal. Chem, 448,33 (1998) [2] K.S. Park, S.O. Jung, S.S. Lee and J.S. Kim, Bull. Kurean Chem. Soc, 21, 909 (2000) [3] H. Tamura, K. Kimura, T. Shono, J. Electroanal. Chem, 115, 115 (1980)
