Cadmium(II)-selective sensors based on dibenzo-24-crown-8 in PVC matrix Original Research Article

Cadmium(II) selective sensors have been fabricated from poly(vinyl chloride) (PVC) matrix membranes containing neutral carrier, dibenzo-24-crown-8 as ionophore and dibutyl(butyl)phosphonate (DBBP), diphenylether (DPE) and 1-chloronaphthalene (1-CN) as plasticizing solvent mediators. Best performance was exhibited by the membrane having a composition crown:PVC:DBBP in the ratio 20:200:200 (w/w). This membrane gives a linear potential response in the concentration range 3.9×10−5–1.0×10−1 M with a Nernstian slope of 30.0±1.0 mV/decade between pH 3.2 and 7.5. It has a fast response time of 25 s, is inert towards acids, salt solutions and non-aqueous media (up to 50% (v/v)). The membrane can be used over a period of five months with good reproducibility. It is selective over a number of mono, bi- and trivalent cations. The practical utility of the sensor has been demonstrated by using it successfully as an indicator electrode in the potentiometric titration of Cd2+ with EDTA and also for the determination of Cd2+ in waste water.