Quantitative Monitoring of Cobalt Ions by a Co2+ Selective Electrode Based on a calix[4]arene Derivative

A highly Co2+ ion-selective polyvinyl chloride (PVC) membrane sensor based on a derivative of calix[4]arene (L) as an excellent sensing material is successfully developed. The electrodes display a Nernstian behavior (29.7 +/- 0.4 mV decade(-1)) over wide Co2+ ion concentration ranges from 1.9x10 (-7) to 1.0x10(-1) M with very low limits of detection (8.4x10 -8 M). The electrodes have a relatively fast response time (<50 s), a satisfactory reproducibility and relatively long life time. The proposed sensor shows a fairly good selectivity toward Co2+ ion in comparison whit other common cations. The potentiometric responses are independent of the pH of the test solutions in the range of 2.5-8.4. The practical utility of the proposed electrodes have been demonstrated by their use in potentiometric titration of cobalt with EDTA. It was also successfully applied in determination of cobalt ions in some aqueous samples.