Analytica Chimica Acta 532 (2005) 153–158 Zinc(II)-selective sensors based on dibenzo-24-crown-8 in PVC matrix V.K. Gupta a,∗ , M. Al Khayat b , A.K. Minocha c , Pankaj Kumar c a Department of Chemistry, Indian Institute of Technology, Roorkee, Roorkee (UA) 247 667, India b Department of Basic Sciences, University of Sharjah, UAE c CBRI, Roorkee, India Received 12 August 2004; received in revised form 26 October 2004; accepted 26 October 2004 Available online 21 December 2004 Abstract Membranes of dibenzo-24-crown-8 (I) as an ion active material in poly(vinylchloride) (PVC) based matrix have been tried for zinc(II)- selective sensors. The effect of anion excluder, sodium tetraphenylborate (NaTPB) and plasticizers, tris(2-ethylhexyl)phosphate (TEP), tributylphosphate (TBP), dibutylphthalate (DBP), dibutyl(butyl)phosphonate (DBBP), 1-chloronaphthalene (CN) and dioctylphthalate (DOP) on the performance of the membrane electrodes has also been studied. It was observed that the membrane having the composition (I): PVC:NaTPB:DOP in the ratio 10:200:2:100 gave the best results with a wide working concentration range of 9.2 × 10 -5 to 1.0 × 10 -1 M, Nernstian slope of 29.0 ± 0. 5 mV/decade of activity, fast response time of 12 s and good selectivity over a number of mono-, bi-, and trivalent cations. The sensor works well in a pH range 4.8–6.2 and can be employed for the estimation of zinc ions in partially non-aqueous medium having up to 10% (v/v) methanol, ethanol or acetone content. The practical utility of the sensor has been demonstrated by using it successfully as an indicator electrode in the potentiometric titration of Zn 2+ with EDTA and also for the determination of Zn 2+ in a real sample analysis of wastewater. © 2004 Elsevier B.V. All rights reserved. Keywords: Crown ether; Potentiometric sensor; Waste analysis; Zinc sensor 1. Introduction Zinc is one of the heavy metals, which is used in paint, electroplating, pharmaceutical and fine chemical industries and thus occurs widely in environment. Also some biomed- ical and a number of process streams contain less ac- tivity of this metal ion. Besides, zinc is also present in high protein foods and its large doses can cause fever, chills, pulmonary manifestation and gastroenteritis. It can also cause vomiting, nausea, anemia and renal failure. In view of its toxicity, the determination of zinc becomes im- portant and for this some ISEs are reported in literature [1–19]. In spite of large amount of work done to develop ∗ Corresponding author. Tel.: +91 1332 285801; fax: +91 1332 273560. E-mail address: vinodfcy@iitr.ernet.in (V.K. Gupta). a good zinc selective electrode, investigations are called for in this direction as the reported sensors have one or other limitations. The cavity size of dibenzo-24-crown-8 (1.05 ˚ A) suits well for the uptake of zinc ions (ionic radii 0.88 ˚ A), there- fore, efforts have been made to prepare a zinc ion se- lective sensor by incorporating dibenzo-24-crown-8 (I) in PVC matrix and the results are presented in this paper. 0003-2670/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2004.10.067