Sensors and Actuators B 105 (2005) 334–339 Novel terbium(III) sensor based on a new bis-pyrrolidene Schiff’s base Mohammad Reza Ganjali a,∗ , Ahmad Ghesmi b , Morteza Hosseini c , Mohammad Reza Pourjavid a , Morteza Rezapour b , Mojtaba Shamsipur d , Masoud Salavati-Niasari e a Department of Chemistry, Tehran University, Tehran, Iran b Circle of Research of Technology Development of Fars, Iran c Department of Chemistry, Tarbiatmodarres University, Tehran, Iran d Department of Chemistry, Razi University, Kermanshah, Iran e Department of Chemistry, Razi University, Kashan, Iran Received 10 April 2004; received in revised form 13 June 2004; accepted 15 June 2004 Available online 14 August 2004 Abstract Here a terbium-selective solvent polymeric membrane sensor based on N,N,-bis(pyrrolidene) benzene-1,2-diamine, poly(vinyl chloride) (PVC), benzylacetate (BA) plasticizer, and an anionic additive is described. At a pH range of 3.5–7.7, this sensor responds to dysprosium in a linear range from 1.0 × 10 -5 to 1.0 × 10 -1 M, with a slope of 19.8 mV per decade and a detection limit of 7.0 × 10 -6 M. It has a fast response time of <20 s in the whole concentration range, and can be used for at least 2 months without any considerable divergences in the potentials. The proposed sensor revealed comparatively good selectivity with respect to common alkali, alkaline earth, transition and heavy metal ions. It was used as an indicator electrode in potentiometric titration of fluoride ions, and in determination of F - ion in some mouth washing solutions preparations. © 2004 Elsevier B.V. All rights reserved. Keywords: Terbium; Potentiometry; Schiff’s base; PVC; N,N,-bis(pyrrolidene) benzene-1,2-diamine 1. Introduction The rare earths are considered only slightly toxic accord- ing to the Hodge–Sterner classification system and thus can be handled safely with ordinary care. Terbium and other lanthanides are used for gasoline-cracking catalysts, carbon arcs, and in movie projectors [1]. Spectrophotometry, spectrofluorimetry, ICP-MS and ICP-AES are the main methods for the low-level moni- toring of terbium ions in solutions [2–5]. Isotope dilution mass spectrometry, neutron activation analysis, X-ray flu- orescence spectrometry [6–8], etc., are also used in some laboratories. These methods are either time consuming, involving multiple sample manipulations, or too expensive for most analytical laboratories. Potentiometric sensors have shown to be very effective tools for analysis of a wide variety of cations, anions, and molecules. They are very simple, inexpensive, and capa- ble of producing reliable responses in a wide concentration ∗ Corresponding author. Tel.: +98-21-6112788; fax: +98-21-6495291. E-mail address: ganjali@khayam.ut.ac.ir (M.R. Ganjali). range. Due to the vital importance of terbium in industry, and the urgent need for a Tb(III)-selective electrode for po- tentiometric monitoring of terbium, we became interested in the preparation of a highly selective and sensitive sensor for determination of this ion. We have recently reported a number of sensors for ions of the lanthanide group elements, such as Ce 3+ [9,10], Yb 3+ [11], La 3+ [12,13], Sm 3+ [14,15] and Gd 3+ [16]. In this work we report a novel Tb(III) membrane sensor base on a new pyrolidene Schiff’s base. To the best of our knowl- edge, this is the first terbium ion-selective membrane elec- trode with a nice Nernstian response over a relatively wide working range. 2. Experimental 2.1. Materials Reagent grade dibutyl phthalate (DBP), acetophenon (AP), benzyl acetate (BA), sodium tetraphenyl borate (NaTPB), tetrahydrofuran (THF), and high relative molec- ular weight PVC were purchased from the Merck chemical 0925-4005/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2004.06.016