The electrochemistry of the inclusion complex of anthraquinone with beta-cyclodextrin studied by means of OSWV

The reduction of anthraquinone (AQ) in the presence of beta-Cyclodextrin (beta-CD) has been investigated by Osteryoung square wave voltammetry (OSWV) in phosphate buffer (pH = 7.0). beta-CD forms a 1:1 inclusion complex with AQ. The experimental results show that beta-CD causes a decrease in the peak current (I-p) and a negative shift in the peak potential (E(p)) for AQ reduction. The relationship between I-p (and E(p)) and the concentration of beta-CD has been studied. The dissociation constant of the inclusion complex, K-d = 3.5 x 10(-3) mol/L, was obtained from the plot of I-p(2) vs. I-p(AQ)(2) - I-p(2)) [CD]. The diffusion coefficients of free AQ and in the presence of beta-CD have been determined by means of chronocoulometry (CC). The adsorption properties of beta-CD on glassy carbon and gold electrodes was investigated. UV-vis spectra gave further evidence for complexation and the dissociation constant determined spectroscopically, K-d' = 4.5 x 10(-3) mol/L, was in agreement with that obtained electrochemically.