Rapid simultaneous electrochemical sensing of tea polyphenols

Simultaneous detection of 1,4-, 1,2- and 1,3-dihydroxy benzene (DHB) isomers on a glassy carbon electrode modified with graphitized mesoporous carbon (GCE/GMC) in pH 7 phosphate buffer solution was demonstrated. GCE/GMC showed absence of any strong adsorption of the DHB isomers on the working electrode surface. The electrochemical response of 1,4-DHB resembled that of 1,2,3-trihydroxybenzene (gallo group) on the GCE/GMC. Differential pulse voltammetry was used as a tool for quantification of the DHB isomers. Constructed calibration plots were linear in the window 4 x 10(-5) to 2.5 x 10(-4), 2.5 x 10(-5) to 2.0 x 10(-4) and 2.5 x 10(-5) to 2.0 x 10(-4) mol L-1 for the 1,4-, 1,2- and 1,3-DHB, respectively. Corresponding detection limits (S/N = 3) were 0.91, 1.31 and 0.67 mu M. Polyphenols extracted from three different tea samples using hot water were successfully analyzed with recovery values similar to 100%.