Zinc(II)-selective sensors based on dibenzo-24-crown-8 in PVC matrix

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 Zn²⁺ with EDTA and also for the determination of Zn²⁺ in a real sample analysis of wastewater.