ASCORBIC ACID DETERMINATION IN FRUIT JUICES BASED ON A FIBRE OPTIC ASCORBIC ACID BIOSENSOR AND FLOW INJECTION ANALYSIS

Abstract

A new method using a fibre optic ascorbic acid biosensor as the detection unit in a flow injection analysis (FIA) system is presented. The biosensor is based on a fibre optic oxygen optrode which measures the oxygen consumption via dynamic quenching of the fluorescence of a dye by molecular oxygen. Ascorbic acid oxidase is immobilised onto the surface of the oxygen optrode as biological component. To detect ascorbic acid in fruit juices it is necessary to protect the biosensor from low pH, such as is present in fruit juices (e.g. lemon juice pH 1.5), using a FIA-system which automatically buffers and dilutes the juice samples.