Environmental significance of the diclofop-methyl and cyclodextrin inclusion complexes

Cyclodextrins (CDs) possess a hydrophilic external surface and a hydrophobic cavity. They are thus highly soluble and, in the meantime, effectively form inclusion complexes with hydrophobic organic compounds to enhance their solubilities. In this study, the complexation between modified beta-CDs and the herbicide diclofop-methyl (DM), (2-(4-(2,4-dichlorophenoxy)-phenoxy) propionate), was investigated. The complexation was confirmed by the shifts in the wavelengths of maximum ultra violet (UV) absorption and fluorescence excitation/emission. The deuterium isotope effects indicate that in the presence of beta-CDs the solubility of DM was lower while that of diclofop was higher in D2O than in H2O, suggesting the primary role of hydrophobic interactions in complexation. The solubility of DM was enhanced in the presence of beta-CDs, the extent of which depended on the modification of beta-CDs. The complexation reduced the hydrolysis of DM and hence increased its stability. The small inconsistency in the power of beta-CDs between hydrolysis retardation and solubilization suggests that hydrolysis was affected by the properties of beta-CDs and the configuration of DM in the complexes. Use of beta-CDs may thus result in the mobilization of soil DM. Properly modified beta-CDs may be utilized as formulation additives for improved delivery of DM and for enhanced environmental remediation.