A new enzyme electrode based on ascorbate oxidase immobilized in gelatin for specific determination of L-ascorbic acid

A biosensor for the specific determination of L-ascorbic acid in fruit juic es and vitamin C tablets was developed using ascorbate oxidase (EC 1.10.3.3 ) from cucumber (Cucumis sativus L.) in combination with a dissolved oxygen probe. Ascorbate oxidase immobilized with gelatin using glutaraldehyde and fixed on pretreated teflon membrane served as an enzyme electrode. The pho sphate buffer (50 mM, pH 7.5) and 35 degrees C were established as providin g the optimum conditions. The biosensor response depends linearly on L-asco rbic acid concentration between 5.0 x 10(-5) and 1.2 x 10(-3) M with a resp onse time 45 s. The biosensor is stable for more than 2 months, while more than 200 assays were performed. The results obtained for fruit juices and t ablets were compared with DCIP (2,6 dichlorophenolindophenol) method. (C) 1 999 Elsevier Science B.V. All rights reserved.