Enzyme-less and selective electrochemical sensing of catechol and dopamine using ferrocene bound Nafion membrane modified electrode

Here in, we are reporting a new membrane modified electrode based on ferrocene (fc) mixed Nafion (Nf) system for enzyme-less and selective electrochemical sensing of catechol and dopamine without any interference from cysteine, uric acid, hydrogen peroxide and ascorbic acid at an applied potential of 200 mV vs. Ag/AgCl in pH 7 phosphate buffer solution. The working electrode, ferrocene-bound Nafion membrane modified glassy carbon electrode (GCE/{Nf-fc}-MME) was prepared by manual mixing of 10 mg of ferrocene with 2% of Nafion solution (optimal) followed by drop coating on the GCE surface, and electrochemical pretreatment by continuous potential cycling in pH 7 PBS. The modified electrode showed well-defined redox behavior at an equilibrium potential (E-1/2) of 150 mV vs. Ag/AgCl in pH 7 PBS due to the electron-transfer reaction of fclfc(+) redox. The calculated exchange current density (I degrees) and apparent heterogeneous rate constant (k(h)(aPP)) were 6.16 x 10(-5) A and 4.51 x 10(-3) cm s(-1) respectively for catechol by electrochemical impedance spectroscopy, which were about 100 times higher over the unmodified electrodes. Different domains of Nafion, namely hydrophilic and hydrophobic sites have a specific role to immobilize the ferrocene species and in turn to selectively mediate catechol and dopamine in a solution mixture containing common physiological interferents. Calibration plots were in the range of 250 mu M-2.5 mM and 250 mu M-5 mM for catechol and dopamine, respectively, with the corresponding detection limit (SIN = 3) values 10.8 mu M and 22.7 mu M. The current sensitivity was 1.1 mu A mM(-1) for both the compounds. The working electrode showed negligible variation in the detection current up to 2 days of measurement.