Abstract

The main aim of this work is to improve the lower detection limit of cadmium selective polymeric membrane. The sensor was fabricated by using thiacalixarene derivative 5,11,17,23-tetra-tert-butyl-25,27-bis-[(3'-methoxy phenyl)methoxy]-26,28-dihydroxy-2,8,14,20-tetrathiacalix [4]arene as ionophore. The membrane with composition of ionophore: PVC: DMP: NaTPB of 3.5% : 33% : 1.0% : 62.5% (w/v) has a standard detection limit of 1.0x10^-8 M and lowest possible detection limit of 6.2x10^-9 M. The electrode exhibits Nernstian response with slope 35.3±1 mV decade^-1 of activity in linear concentration range of 4.2x10^-8 to 1.0x10^-1 M for Cd²⁺ ion, performs satisfactorily over wide pH range (1.5–7.0), with a fast response time (5s). The selectivity coefficients determined by using fixed interference method (FIM) indicate high selectivity for Cd²⁺ as compared to other tested cations. The practicable utility of electrode has been demonstrated in the titration of Cd²⁺ with standard EDTA solution. The proposed electrode was successfully used for the determination of Cd²⁺ in different biological and environmental samples.

Keywords

Thiacalix[4]arene, Cadmium, ion-selective electrode, PVC, lower detection limit.