A new PVC membrane potentiometric sensor that is highly selective to Tb(III) ions was prepared by using 4-amino-3-{2-[4-amino-6-methyl-5-oxo-4,5-dihydro-1,2,4-triazin-3(2H)-yliden] hydrazono}-6-methyl-3,4-dihydro-1,2,4-triazin-5(2H)-one (ATO) as a suitable carrier. The sensor works satisfactorily in the concentration range of 1.0 × 10-6 to 1.0 × 10-1 mol L-1 (detection limit 8.6 × 10-7 mol L-1) with a Nernstian slope of 19.4 ± 0.5 mV per decade of activity. This electrode showed a fast response time (~15 s) and was used for a period of more than 2 months. The potentiometric selectivity coefficient values (for mono-, di-, and trivalent cations) as determined by the match potential method (MPM) indicate good response for Tb3+ in the presence of interfering ions. The membrane sensor was used as an indicator electrode in the potentiometric titration of Tb(III) ions with EDTA. It was also applied to the determination of fluoride ions in mouth wash preparation sample and the Tb3+ recovery from various binary mixtures.
4-amino-3-{2-[4-amino-6-methyl-5-oxo-4,5-dihydro-1,2,4-triazin-3(2H)-yliden] hydrazono}-6-methyl-3,4-dihydro-1,2,4-triazin-5(2H)-one; terbium; potentiometry; ion-selective electrode
