Determining the stoichiometry and binding constants of inclusion complexes formed between aromatic compounds and β-cyclodextrin by solid-phase microextraction coupled to high-performance liquid chromatography

Abstract The complexation of native β-cyclodextrin (CD) and seven aromatic compounds, namely, phenetole, toluene, m-xylene, naphthalene, biphenyl, fluorene and phenanthrene, has been studied for first time utilizing a solid-phase microextraction (SPME)–high-performance liquid chromatography (HPLC) method. The stoichiometries of the analyte:β-CD complexes were found to be either 1:1 or 1:2. The formation of 1:2 complexes was confirmed for naphthalene, biphenyl, fluorene, and phenanthrene only when utilizing relatively high concentrations of β-CD (up to 6.6 mM). The 1:2 stoichiometries were confirmed using the classical modified Benesi–Hildebrand (BH) method. The calculated binding constants for 1:1 stoichiometries ( K 1 ) using the SPME method varied from 115.3 M −1 for toluene to 3510 M −1 for phenanthrene, whereas the corresponding values to the 1:2 stoichiometries ( K 3 ) varied from 7.30 × 10 5  M −2 for biphenyl to 9.03 × 10 6  M −2 for naphthalene.