Selective Detection of Ascorbic Acid Using Octacyanomolybdate-Doped-Glutaraldehyde-Cross-Linked Poly-L-Lysine Film Modified Glassy Carbon Electrode

摘要

The present work describes oxidation of ascorbic acid (AA) at octacyanomolybdate-doped-glutaraldehyde-cross-linked poly-L-lysine (PLL-GA-Mo(CN)(8)(4-)) film modified glassy carbon electrode in 0.1 M H2SO4. The modified electrode has been successfully prepared by means of electrostatically trapping Mo(CN)(8)(4-) mediator in the cationic film of glutaraldehyde-cross-linked poly-L-lysine. The dependence of peak current of modified electrode in pure supporting indicates that the charge transfer in the film was a mixed process at low scan rates (5 to 200 mV s(-1)), and kinetically restrained at higher scan rates (200 to 1000 mV s(-1)). Cyclic voltammetry and rotating disk electrode (RDE) techniques are used to investigate the electrocatalytic oxidation of ascorbic acid and compared with its oxidation at bare and undoped PLL-GA film coated electrodes. The rate constant of catalytic reaction k obtained from RDE analysis was found to be 9.5 x 10(5) cm(3) mol(-1) s(-1). The analytical determination of ascorbic acid has been carried out using RDE technique over the physiological interest of ascorbic acid concentrations with a sensitivity of 75 mu A inM(-1). Amperometric estimation of AA in stirred solution shows a sensitivity of 15 mu A mM(-1) over the linear concentration range between 50 and 1200 mu M. Interestingly, PLL-GA-Mo(CN)(8)(4-) modified electrode facilitated the oxidation of ascorbic acid but not responded to other electroactive biomolecules such as dopamine, uric acid, NADH. glucose. This unique feature of PLL-GA-Mo(CN)(8)(4-) modified electrode allowed for the development of a highly selective method for the determination of ascorbic acid in the presence of interferents.