Spectroscopic study of orange G-β-cyclodextrin complex and its analytical application

The mechanism of the inclusion of orange G and beta-cyclodextrin (beta-CD) has been studied by using both spectrophotometry and infrared spectroscopy. Effects of the pH, concentrations of beta-CD, and ionic strength on the inclusion complex of beta-CD and orange G were examined. The result showed that orange G reacts with beta-CD to form a 1:1 host-guest complex with an apparent formation constant of 3.03 x 10(3) Mol(-1) l. The thermodynamic parameters of inclusion complex, Delta G(0), Delta H-0, and Delta S-0 were obtained. Based on the enhancement of the absorbance of orange G produced through complex formation, a ratiometric method spectrophotometrically for the determination of orange G in bulk aqueous solution in the presence of beta-CD was developed, which overcome the effect of condition change on the determination of orange G. The linear relationship between the absorbance and orange G concentration was obtained in the range of 1.0 x 10(-5) to 4.0 x 10(-5) mol l(-1), with a correlation coefficient of 0.9998. The detection limit was 3.6 x 10(-6) mol l(-1). The principal advantage of the proposed method is high accuracy because ratiometry was used in measurement. (c) 2006 Elsevier B.V. All rights reserved.