ABSTRACT
Poly(vinyl chloride) (PVC) based membranes containing 4-tert-butylcalix[4]arene (I) as an electroactive material along with anion excluder sodiumtetraphenylborate (NaTPB) and plasticizer tri-butylphosphate (TBP) have been developed to fabricate a new zinc-selective sensor. Out of various compositions, the best performance was exhibited by the membrane having I, NaTPB, TBP and PVC in the ratio 8:5:100:200 (w/w). The sensor works well in the concentration range 9.8 x 10(-6) to 1.0 x 10(-1) mol dm(-3) with a near-Nernstian slope of 28.0+/-1.0 mV/decade of activity. The detection limit is down to 5.0 x 10(-7) mol dm(-3). The working pH range of this sensor is 2.5-4.3 and it works well in partially non-aqueous medium up to 15% (v/v) (methanol, ethanol and acetone). It exhibits a fast response time of 30s and could be used for more than four months without any considerable change in response characteristics. It has excellent selectivity for Zn(II) over other mono-, bi- and trivalent cations which have been reported to cause interference in the working of other sensors. It has been successfully used as an indicator electrode in the potentiometric titration of Zn(II) against EDTA and also to estimate zinc ions in industrial waste waters.
ABSTRACT
The potentiometric response characteristics of Cu(2+)-selective electrodes based on bis(acetylacetone)propylenediimine (I) combined with anion localizing agent (sodium tetraphenyl borate (NaTPB)) and solvent mediators (dibutyl butyl phosphonate (DBBP), tri-n-butyl phosphate (TBP) and chloronaphthalene (CN)) were investigated. The best results for Cu(2+) sensing was obtained for the electrode membrane containing PVC, I, DBBP and NaTPB in composition 5:100:200:6 (I:PVC:DBBP:NaTPB) (w/w; mg), where the electrode had a Nernstian response (30.0mV/decade) to Cu(2+) within the concentration range 1.0x10(-5) to 1.0x10(-1)M and detection limit of 0.5ppm. The operational pH range of the electrode was 3.3-7.0. Selectivity characteristic of the proposed electrode was also assessed by calculating K(A,B)(Pot) using fixed interference method matched potential method. The sensor has been successfully used in the potentiometric titration of copper ions with EDTA.
