Cyclopentanol-Enhanced Solubilization of Polycyclic Aromatic Hydrocarbons by Cyclodextrins

The effect of cyclopentanol on the solubilization of six polycyclic aromatic hydrocarbons (PAHs) by β-cyclodextrin (β-CD) and γ-cyclodextrin (γ-CD) is reported in this paper. The addition of 0.1% v/v cyclopentanol significantly enhances the solubilization power of β-CD for pyrene, acenaphthene, phenanthrene, and fluoranthene, which form 1:2 complexes with β-CD. However, the solubilization of acenaphthene and phenanthrene by β-CD in the presence of cyclopentanol decreases at higher β-CD concentrations following an initial increase. This phenomenon is attributed to the cyclopentanol-induced formation of insoluble β-CD aggregates. In contrast, cyclopentanol produces no pronounced effect and a marked decrease in the solubilization power of β-CD for naphthalene and anthracene, respectively. These two compounds form 1:1 complexes with β-CD. The solubilization of all six PAHs by γ-CD is significantly enhanced by 1% v/v cyclopentanol. This result indicates that the addition of cyclopentanol increases the “hyd rophobicity” of the γ-CD cavity and increases the solubilization power of γ-CD without inducing structure-dependent selectivity. On the basis of linearity and nonlinearity observed in the solubilization curves of the six PAHs in the presence of cyclopentanol, it is suggested that naphthalene, anthracene, acenaphthene, and phenanthrene form 1:1 complexes with γ-CD while fluoranthene and pyrene form both 1:1 and 2:2 complexes.