LACCASE-NAFION BASED BIOSENSOR FOR THE DETERMINATION OF POLYPHENOLIC SECONDARY METABOLITES

A laccase-based biosensor was developed by specific enzyme adsorption on screen-printed working electrodes of DROPSENS cells, and stabilized with Nafion 0.1% membrane. The electrode was characterized with respect to response time, sensitivity, linear range, detection limit, pH dependence, interferences, and long-term stability. The tested substrates were catechol, rosmarinic acid, caffeic acid, chlorogenic acid, and gallic acid. The optimized biosensor proved the following characteristic performances: the apparent Michaelis Menten calculated considering rosmarinic acid substrate 8.3 x 10(-6) molL(-1) (r = 0.995, n = 6); the dynamic range of biosensor response for rosmarinic acid 7 x 10(-7) -1.5 x 10(-6) mol L-1; the detection limit for rosmarinic acid 1.19 x 10(-7) molL(-1) (RSD 1.08%, n = 3). It was noticed that the biosensor reaches systematically 90% to 94.3% from the response obtained by LC-DAD-ESI-MS for real samples.