Tris(2,4,6-trimethoxyphenyl)polysulfone-methylene quaternary phosphonium chloride (TPQPCl) ionomer chemically modified electrodes: An electroanalytical study towards sensing applications

Abstract We report for the first time the redox properties of an anion-exchange ionomer membrane, tris(2,4,6-trimethoxyphenyl)polysulfone-methylene quaternary phosphonium chloride (TPQPCl). TPQPCl was solubilized in ethanol/water solutions and films of TPQPCl at different concentrations were drop casted on glassy carbon electrodes. The thickness of TPQPCl films in dry conditions was evaluated using profilometer. The anion-exchange properties and charge transport properties of TPQPCl coated electrodes were investigated using K 4 Fe(CN) 6 as anionic redox probe. The permselectivity properties of TPQPCl coated electrodes were assessed using hexaammine ruthenium(II) chloride. Cyclic voltammetry performed at low scan rate was utilized to determine the concentration of the redox mediator inside the films, with the apparent diffusion coefficient values of different TPQPCl coating estimated using both the Randles-Sevcik equation and the Anson's method. We found the concentration of the ferro/ferricyanide couple redox within the TPQPCl films in the order of 10 −2 -10 −1  mol dm −3 , with values of D app in the order of 10 −9  cm 2  s −1 . TPQPCl drop casted films evidenced good preconcentration capabilities towards incorporation of anions. To ascertain the suitability of the ionomer coated films towards the electroanalytical detection of anions, TPQPCl coated electrodes were utilized for the voltammetric detection of nitrites in tap and river waters. The results showed that TPQPCl coated electrodes are suitable to quantify nitrites in fresh waters with a limit of detection, LoD, of 1.07 μM, sensitivity as 0.267 μA μM −1  cm −2 and linear range between 1 μM and 500 μM.