A colourimetric sensor for the simultaneous determination of oxidative status and antioxidant activity on the same membrane: N,N-dimethyl-p-phenylene diamine (DMPD) on Nafion.

•Membrane sensor developed for determination of oxidative status and antioxidant activity.•N,N-Dimethyl-p-phenylene diamine hydrochloride (DMPD) oxidized to quinone by ROS.•The pink colour of sorbed cationic radicals on Nafion decreased in presence of antioxidants.•The decrease in absorbance (ΔA) of sensor varied linearly with antioxidant concentration.•The antioxidant activity sensing method was validated for synthetic and real mixtures.