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 Kmapp 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.