Cobalt (II) Selective Electrode Based on Benzo-15-Crown-5 in PVC Matrix

Abstract: The present work deals with a poly (vinyl chloride) (PVC) based membrane incorporating benzo-15-crown-5 as an ionophore which has been prepared and explored as Co2+ cation selective sensor. The strengths of the ion–ionophore (Co2+– benzo-15-crown-5) interactions and the role of ionophore on membrane performance have been studied. The ligand coordination with the ion investigated via IR and UV-Vis spectroscopy [1]. The UV spectra absorption of benzo-15-crown-5, Co2+ ion and their mixture recorded over 250–400 nm. The substantial change in the absorbance of ionophore after contact of the carrier solution with Co2+ ions, revealed the specific and strong interaction between the ionophore in the membrane and cobalt (II) ions [2]. Surface morphology of the Co2+ selective membrane was investigated by using a scanning electron microscopy (SEM). The results obtained by SEM are in good agreement with the potentiometric response of the electrode. The electrode exhibited a linear response with a near Nernstian slope of 29.21 ±0.24 (mV per decade of activity) over the pH range from 2 to 6 with a satisfactory concentration range of 1.0×10−6 to 1.0×10−1 M. The value of 9.0×10-7 M was obtained as lower detection limit for the fabricated electrode. The developed sensor exhibited good reproducibility over a period of about 10 weeks with a fast response time of 10 seconds. The proposed sensor was successfully applied as an indicator electrode for the potentiometric titration of a cobalt (II) solution with EDTA.