A tetradecylphosphonium compounds–based membrane sensor for potentiometric quantitation of pertechnetate-ions in cementitious radioactive waste

Abstract

A novel potentiometric sensor has been developed for the determination of pertechnetate ions (TсO4‾) by using on two synthesized tetradecylphosphonium salts, tetradecylphosphonium pertechnetate and tetradecylphosphonium tetraphenylborate, as sensing components of a poly (vinyl chloride) matrix membrane. Potentiometric studies have confirmed the improvement in response characteristics of the sensor based on the membrane system containing a mixture of both tetradecylphosphonium salts. Such sensor exhibits a stable Nernstian response over a wide concentration range of pertechnetate ions (10−2 – 5 × 10-7 M) in aqueous solutions with the acidity from 3 M HCl to pH 12. The lower limit of detection is 0.15 μM. The calculated potentiometric selectivity coefficients moderate selectivity for TсO4‾ ions over the interfering anions and these values are clearly in agreement with the standard Gibbs energies of the ions transfer between water and NPOE. The reported sensor was successfully employed for the pertechnetate quantitation in the radioactive waste disposal products (cement cubes).