Redox active films of salicylic acid-based molecules as pH and ion sensors for monitoring ionophore activity in supported lipid deposits

5-aminosalicylic acid and salicylic acid have been used to form redox active films onto glassy carbon electrodes through recurrent cyclic voltammetry. The variation of the formal potential of the film obtained from 5-aminosalicylic acid as a function of pH is linear over the entire pH range studied (pH 2 to 10) with a slope of -80 mV per pH unit. Salicylic acid-based redox active films permit the detection of sodium and potassium ions (with a slope of -10 mV per 1 mM of cation) and chloride (with a slope of +11 mV per 1 mM of chloride). A lipid deposit of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) onto these modified electrodes allowed the integration of ionophores (valinomycin and nigericin) and the monitoring of the pH and potassium ion concentration variation at the modified electrode/ lipid deposit interface. (C) 2019 Elsevier Ltd. All rights reserved.