A reduced graphene oxide based biosensor for high-sensitive detection of phenols in water samples

Laccase (Lac) from Rhus vernificera was covalently immobilized onto 1-aminopyrene (1-AP) functionalized reduced graphene oxides (rGOs)-modified glassy carbon electrode by encapsulation with chitosan. The biosensor was characterized with respect to the optimum pH and polarized potentials for the determination of phenols, and its response time, sensitivity, linear range, detection limit, and stability. Hydroquinone and catechol were selected as the analytes and detected based on the direct electron transfer behavior of Lac and its enzymatic oxidation of analyte. The sensitivities of the electrode were 14.16, 15.79 μA mM−1 with linear ranges of 3–2000, 15–700 μM for hydroquinone and catechol, respectively. The detection limits (S/N = 3) were 2 and 7 μM for hydroquinone and catechol, respectively with a fast response time (t95%) of less than 5 s. Moreover, the immobilized Lac showed high affinity to hydroquinone and catechol with Kmapp values of 5 and 0.3 mM, respectively. As a consequence, the biosensor demonstrated suitable stability (ca. 7 days; over 300 determinations) and good repeatability with a relative standard deviation of 3.96%. The recovery study of hydroquinone in real water samples gave values from 82.7% ± 10% to 105.9% ± 8%, confirming its application potential in the measurement of phenols in real samples.