Abstract

The concentration dependent self - association of 5-caffeoylquinic acid and its complexation with sodium have been determined by UV-Vis spectroscopy. The self - association and hetero - association constants were determined by dimer model and Benesi - Hildebrand equations. The equilibrium con-stants for the formation of dimer and complexation with sodium at wavelength of 324 nm and 370 were 1813, 13529  respectively. Using the value of dimerzation constant the fraction of monomer and dimer were calculated for every concentration of 5-caffeoylquinic acid. The deviation of molar extinction coefficient from Beer -Lambert’s law and existence of isobestic points at different wave-lengths showed the existence of dimerzation and the formation of the complexes in the solution respectively.

Key words: 5-caffeoylquinic acid, UV-Vis spectroscopy, thermodynamic, self-association, hetero-association.