Inclusion complexes of pesticides in aqueous solutions of methylated-β-cyclodextrin

Abstract

Disadvantage of some organic pesticides is their low water solubility. Among other substances, cyclodextrins and modified cyclodextrins were considered as agents for improving pesticides water solubility. The solubility of poorly soluble pesticides, dimethoate, simazine, linuron and thiram, was determined in aqueous solution of methylated-β-cyclodextrin (mbCD) by ultraviolet spectrophotometry. Methylated-β-cyclodextrin was obtained by the modified Hawort method and characterized by 1H NMR and HPLC data. The average degree of substitution was 13.8. Methylation was done either on C-2, C-3, and C-6 atoms of glucopyranose unit therefore obtained product can be assort as randomly mβCD. Solubility of the studied pesticides in aqueous solution of mβCD increases in relation to their solubility in water for dimethoate 506, for simazine167, for thiram 44, and for linuron 20 times. Reactions of dimethoate and simazine with mβCD were entropy-driven while the inclusion complexation of mβCD with the linuron and thiram were driven by both, enthalpy and entropy, as determined by calorimetric measurements. The observed solubility increment of the investigated pesticides in aqueous solution of mβCD, suggests that it can be efficiently used in pesticide solutions formulations and increase their bioavailability, and biodegradability.

Keywords

• inclusion complexes
• methylated-β-cyclodextrin
• pesticides