Chronopotentiometric method for the assessment of ionophore diffusion coefficients in solvent polymeric membranes

A chronopotentiometric method is proposed for the determination of the diffusion coefficients of free ionophores in solvent polymeric membranes. For the pH sensitive chromoionophore ETH 5294, the method was shown to give diffusion coefficients that correlate well with those assessed by both optical and chronoamperometric methods. The limit of applicability of the chronoamperometric and chronopotentiometric methods in terms of membrane composition and experimental parameters has been identified. The chronopotentiometric method was successfully used to determine the diffusion coefficients of eight ionophores and proved to be more robust and more widely applicable than the previously reported chronoamperometric and optical methods.