Application of Calixarene Ionophores in Pvc-Based Ion Selective Electrodes for Heavy Metal Detection

Functionalized calixarene molecules 26, 28-dihydroxy-25, 27-dimethoxycalix[4]arene-11, 23-diphosphonic acid for Pb(II) and 25, 26, 27, 28-tetra-(2-dimethydithiocarbamolyethoxy) calix[4]arene for Hg(II) were tested as possible ionophores in Ion Selective Electrodes (ISEs) and successfully applied for the detection of heavy metal ions from environmental and industrial wastewaters. These membrane electrodes based on calixarene sensors are active in the pH range of 5.5-8.5. Calixarene sensors worked satisfactorily in aqueous as well as non-aqueous media up to 25% (v/v) non-aqueous content, and the life time of the sensors was observed to be five months. Potentiometric selectivity coefficients as determined by Match Potential Method (MPM) indicate excellent selectivity for Pb2 and Hg2 ions. The sensors could be used successfully in the estimation of lead and mercury in electrochemical battery wastes and also as indicator electrodes in potentiometric titration.