Amperometric biosensor for ascorbic acid

A L-ascorbic acid biosensor based on ascorbate oxidase has been developed. The enzyme was extracted from the mesocarp of cucumber (Cucumis sativus) by using 0.05 mol L phosphate buffer, pH 5.8 containing 0.5 mol L NaCl. After the dialysis versus phosphate buffer 0.05 mol L pH 5.8, the enzyme was immobilized onto nylon net through glutaraldehyde covalent bond. The membrane was coupled to an O 2 electrode and the yielding reaction monitored by oxygen depletion at -600 mV using flow injection analysis optimized to 0.1 mol L phosphate buffer pH 5.8, as the carrier solution and flow-rate of 0.5 mL min. The ascorbic acid calibration curve was linear from 1.2x10 to 1.0x10 mol L. The evaluation of biosensor lifetime leads to 500 injections. Commercial pharmaceutical samples were analyzed with the proposed method and the results were compared with those obtained by high-performance liquid chromatography (HPLC).