A PVC-based 12-crown-4 membrane potentiometric sensor for zinc (II) ions

Poly(vinyl chloride)-based membranes of 12-crown-4 have been fabricated using sodium tetraphenylborate (NaTPB) as an anion excluder and dibutylphthalate (DBP) and dioctylphthalate (DOP), as plasticizing solvent mediators. The best sensor having composition crown: NaTPB: PVC: DOP in the ratio 1:1:10:10 exhibits linearity in the concentration range 7.0 x 10(-5)-1.0 x 10(-1) mol dm(-3) with a Nernstian slope of 29.5 +/- 1.0 mV per decade of concentration. The response time (t(95)) of the sensor is < 10 s and it can be used for a period of 3 months without any divergence in potentials. The sensor performs satisfactorily between pH 2.8 and 5.5 and in non-aqueous solutions containing up to 25% (v/v) alcohol content. It exhibits good selectivity over a number of cations and was used as an indicator electrode in the potentiometric titration of Zn2+ with EDTA. The determination of zinc concentration in the water of a local river has been successfully achieved with the membrane sensor. (C) 1999 Elsevier Science S.A. All rights reserved.