Hydroquinone modified chitosan/carbon film electrode for the selective detection of ascorbic acid

A redox active polymer, hydroquinone modified chitosan (Q-chitosan) was synthesized and characterized by IR and (1)H NMR spectroscopy. The nanocomposite of Q-chitosan with carbon was prepared and used to construct a stable conductive film on the electrode surface. The SEM studies confirms that the Q-chitosan/C composite covers the electrode surface with polymer embedded 50 nm size carbon particles. The formal redox potential, E(0) of the Q-chitosan/C composite modified electrode is evaluated to be 0.09 V vs. Ag/AgCl at pH 7 and the composite electrode shows an excellent electrocatalytic activity toward the ascorbic acid (AA) at 0.0 V vs. Ag/AgCl. It is more negative potential than the similar AA biosensors and the lower potential oxidation of AA enabled the selective detection of AA over major interferences such as dopamine and uric acid. Using amperometric method, the linear range for ascorbic acid is estimated to be 10 μM to 5 mM with the detection limit of 3 μM and the sensitivity is 0.07 6μA μM(-1)cm(-2).