Amperometric detection of catechol and catecholamines by immobilized laccase from DeniLite

DeniLite laccase immobilized Pt electrode was used for detection of catechol and catecholamines. The enzymatically oxidized substrates were measured amperometrically. The sensitivities are 210, 75, 60 and 45 nA/muM with the upper limits of linear ranges of 58, 40, 55 and 55 muM and the detection limits (S/N=3) of 0.07, 0.2, 0.3 and 0.4 muM for catechol, dopamine (DA), norepinephrine (NEPI) and epinephrine (EPI), respectively. The response time (t(90%)) is about 2 seconds for each substrate and the long-term stability is around 40-50 days with retaining 80% of initial activity. The very fast response and the remarkable long-term stability are the principal advantages of this sensor. In case of catechol, the pH response of the sensor is mainly determined by enzyme's pH profile, however, in case of catecholamines, both enzyme's pH profile and reversibility of the substrate are operated and the optimal pHs for NEPI and EPI shift towards acidic range compared to that for DA. The presence of ascorbic acid (< 50 muM) did not interfere with the measurement.