Redox protein-polymer films for simultaneous determination of ascorbic acid and hydrogen peroxide

Layer by layer films of protein and redox polymer were constructed and used to simultaneously analyze ascorbic acid and hydrogen peroxide. The films were made using hemoglobin and poly[4-vinylpyridine Os(bipyridine)(2)Cl]-co-ethylamine (Pos-Ea). The film growth was monitored using cyclic voltammetry, quartz crystal microbalance (QCM) and atomic force microscopy (AFM). Reversible pairs of oxidation-reduction peaks were observed using cyclic voltammetry corresponding to the Os(II)/Os(III) from redox polymer and HbFe(III)/HbFe(II) redox couples at 0.35 and -0.25 V vs. Ag/AgCl, respectively. The two redox centers were independent of each other. This enabled the simultaneous and independent determination of ascorbic acid and hydrogen. Peak currents were linearly related to concentration for both analytes in a mixture. The linear range of ascorbic acid was 0-1 mM (R(2) = 0.9996, n = 5) at scan rate of 50 mV s(-1) (sensitivity 3.5 microA/mM) while hydrogen peroxide linear range was 1.0-10.0 microM (R(2) = 0.991, n = 6) with sensitivity of 1.85 microA/microM.