SIMULTANEOUS KINETIC-BASED DETERMINATION OF FRUCTOSE AND ASCORBATE WITH A ROTATING BIOREACTOR AND AMPEROMETRIC DETECTION - APPLICATION TO THE ANALYSIS OF FOOD SAMPLES

A recently introduced biosensor comprising a rotating bioreactor and a stationary platinum ring amperometric detector (Anal. Chem. 1993, 65, 636-639) has been utilized for the simultaneous determination of fruc tose and ascorbate. The approach has been successfully applied to the simultaneous determination of these analytes in fresh food samples. He xacyanoferrate(II) is the monitored species at +0.380 V vs a Ag/AgCl, 3 M NaCl reference. The determination takes advantage of a fast chemic al oxidation of ascorbate by hexacyanoferrate(III) ions and the subseq uent slower production of hexacyanoferrate(II) in the D-fructose 5-deh ydrogenase-catalyzed reaction between D-fructose and hexacyanoferrate( III) as acceptor. D-Fructose 5-dehydrogenase (EC 1.1.99.11) was incorp orated into the rotating disk reactor in immobilized form and on contr olled-pore glass via the glutaraldehyde attachment and cross-linking w ith bovine serum albumin. Sample/reagent processing was accomplished b y programmed continuous-flow/stopped-flow/continuous-flow operation.