ONLINE MONITORING OF GALACTOSIDE CONJUGATES AND GLYCEROL BY FLOW-INJECTION ANALYSIS

A biosensor attached to a flow injection analysis (FIA) system was dev eloped for the automatic determination of galactoside conjugates and g lycerol. The biosensor was based on the enzymatic reaction of galactos e oxidase (GalOD) using galactose, raffinose, lactose and glycerol as substrates. GalOD converts galactoside conjugates to galactohexodialdo se conjugates and glycerol to glyceraldehyde with formation of hydroge n peroxide and consumption of oxygen. Variation of dissolved oxygen in the carrier was estimated utilizing an amperometric oxygen probe. The FIA system consisted in a multichannel peristaltic pump, an injection valve and an electronic transducer which were controlled by the CAFCA software. Stability of the enzyme and optimal working condition were investigated. Optimum pH for the immobilized enzymes under these exper imental conditions was 7.4 and the enzyme retained 80% of the original activity after two months of use. Studies on the dynamical response o f the biosensor showed that the elapsed time between two successive in jections could be as short as 120 s without signal deterioration when the flow rate was 2 ml/min and 50 mu l of injection volume. Sensitivit y of the biosensor was higher for galactose followed by raffinose, lac tose and glycerol. The sensor showed linear response between 0.2 and 2 mM for galactose, 0.5 and 6 mM for raffinose, 25 and 250 mM for lacto se, and 2 and 200 mM for glycerol. (C) 1998 Published by Elsevier Scie nce B.V. All rights reserved.