Amperometric biosensor for the quantification of gentisic acid using polyphenol oxidase modified carbon paste electrode

The affinity of mushroom polyphenol oxidase (PPO) towards gentisic acid (GA ), a metabolite of acetyl salicylic acid (ASA), is demonstrated by spectrop hotometry and by electrochemical techniques. The enzyme can selectively rec ognize GA even in the presence of large excess of ASA and its metabolic der ivatives (salicylic acid (SA) and salicyluric acid (SUA)). At -0.150 V, the sensitivity is (6.1 +/- 0.1)x 10(4) NAM(-1), the response is linear up to 2.0 x 10(-4) M and the detection limit is 5.0 x 10(-5) M. The kinetic param eters, obtained from Eadie-Hofstee plots, are I-max = 51.4 nA and K-m(app) = 6.7 x 10(-4) M. (C) 2000 Elsevier Science B.V. All rights reserved.