PVC based monoaza-18-crown-6 membrane potentiometric sensors for cadmium

Cadmium(II) ion selective sensors have been fabricated from poly(vinyl chlo ride) (PVC) matrix membranes containing neutral carrier, monoaza-18-crown-6 . sodium tetraphenyl berate (NaTPB) as an anion excluder and dibutylphthala te (DBP) and dioctylphthalate (DOP) as plasticizing solvent mediators. The membrane having the composition crown:NaTPB:PVC:DOF in the ratio 1:1:10: 10 exhibits best results with linear potential response in the concentration range 1.0 x 10(-5)-1.0 x 10(-1) M with a detection limit of 1.12 mg/L and a Nernstian slope of 29.0 mV/decade between pH 5.0-7.7. The sensor exhibits a fast response time of < 10 s, is inert towards acids, salt solutions and nonaqueous media (upto 35% (v/v)) and was used over a period of 3 months wi th good reproducibility. It is selective over a number of mono-, bi-, and t rivalent cations. The practical utility of the sensor has been demonstrated by using it as an indicator electrode in the potentiometric titration of C d2+ with EDTA and also for the determination of Cd2+ in waste water.