(accumulation was performed at −0.6 V vs. Ag|AgCl). Voltammograms were obtained with a solution of 0.31, 0.40 and 0.39 mg L−1, for trans-chalcone, CD and XN, respectively, in phosphate buffer, 0.1 mol L−1, pH 7. Inset: the slopes obtained by linear regression vs. the accumulation time.