NEW SILVER ION-SELECTIVE PVC MEMBRANE AND COATED-GRAPHITE ELECTRODES BASED ON A NOVEL CALIX[4]ARENE DERIVATIVE

A new PVC membrane and a coated graphite electrode (CGE) based on a recently synthesized calix[4]arene compound of 5,11,17,23-tetra-tert-butyl-25,27-metoxy-26,28-bis(potassiumksantato)etoxycalix[4]arene as a suitable carrier for silver (I) ion are described. The electrodes exhibit a Nernstian slope of 57.7 +/- 1.3 mV/p[Ag] for PVC membrane electrode and 54.7 +/- 2.1 mV/p[Ag] for CGE over a wide concentration range from 1.0 10(-2) to 1.0x10(-6) M and 1.0x10(-2) to 1.0x10(-5) M, respectively. They have a fast response time (similar to 10 s) and can be used for at least 60 days for PVC membrane electrode and 30 days for CGE without any considerable divergence in potentials. The proposed electrodes show high selectivity towards silver (I) ions with respect to alkali, alkaline earth and several transition and heavy metal ions. Only interference of Hg2+ is found. The potentiometric responses are independent of the pH of test solution in the pH range of 2.0-6.0. Application of only PVC membrane electrode as an indicator electrode in potentiometric titrations of chloride, bromide and iodide ions was reported.