Amperometric detection of mono- and diphenols at Cerrena unicolor laccase-modified graphite electrode:: correlation between sensitivity and substrate structure

Graphite electrode modified with laccase from Cerrena unicolor served as a biosensor for detection of 30 phenolic compounds with different structures. Some correlations of the sensor response to the structures of substrates are discussed. This biosensor responded to: (i) nanomolar concentrations of some of the selected phenolic compounds, e.g., 2,6-dimethoxyphenol,coniferyl alcohol, caffeic acid, DOPAC and hydroquinone, (ii) micromolar concentrations, e.g., ferulic acid, syringic acid, dopamine, 3,4-dihydroxybenzoic acid and DL-noradrenaline, and (iii) millimolar concentrations in the case of phenol and 4-hydroxybenzaldehyde. Among the ortho- or para-substituted phenols, the sensitivity of the C unicolor laccase-modified electrode increased in the following order -H, -CH3, -OH, -OCH3 and -NH3+ but in the case of para-substituted phenols, the K-m(app) values were lower. The sensitivity of the laccase electrode increased with an additional -OH group in para-substituted phenols. In the case of the selected compounds, kinetic data from electrochemical flow injection system were compared with those obtained from experiments in solution. (c) 2005 Elsevier B.V. All rights reserved.