Determination Of Stability Constant For Different Metal Ions Using Sandwich Membrane Method

Abstract

A segmented sandwich membrane method is used to determine complex stability constants of two thiuram ionophores in solvent polymeric sensing membranes. These ionophores are commonly used in potentiometric and optical sensors, and knowledge of such binding information is important for ionophore and sensor design. In this method, two membrane segments are fused together, with only one containing the ionophore, to give a concentrationpolarized sandwich membrane. Unlike other approaches, this method does not require the use of a reference ion in the sample and/or a second ionophore in the membrane, and is typically pH insensitive. The two ionophores TMTMS and TMTDS responsive for the cations copper and aluminium ions are characterized and discussed. The logarithmic complex stability constant 6.79 for Cu2+ and 6.65 for Al3+ are find out be the maximum among all the metal ions analysed. From the observed complex stability constants, maximum possible selectivities are calculated that would be expected if interfering ions show no binding affinity to the ionophore, Each ionophore is characterized in poly(vinyl chloride) membranes plasticized with a polar (NPOE).