Formação e caracterização de complexos de inclusão entre atrazina e ciclodextrinas suportadas em sílica

Abstract

Atrazine (ATZ) is one of the most used agrochemicals around the world, since it is important in conservation tillage in order to increase productivity and decrease erosion. The main issues concerning the usage of ATZ are related to leaching and toxicity. Cyclodextrins (CD) and cyclodextrins functionalized in silica (CDSI) have been proving to be effective alternatives to avoid these issues, changing the liberation of the guest molecules and reducing toxicity. Inclusion complexes between ATZ and CD (ATZ/α-CD; ATZ/ɣ-CD) and CDSI (ATZ/α-CDSI; ATZ/ɣ-CDSI) have been prepared and characterization tests (infrared and differential scanning calorimetry) have been conducted. These tests indicated the inclusion of ATZ in the cavity. Phase solubility has shown that the stoichiometry is 1:1. Liberation tests have shown that all samples had a slower liberation in comparison with the uncomplexed ATZ. The ATZ/ɣ-CDSI reduced the liberation speed in 75%. In liberation tests conducted in soil columns, the samples had the same reactions due to possible interactions in the soil. Bioassays with Lactuca sativa have indicated that all samples were less toxic than uncomplexed ATZ. In the chromosome aberration test, there was reduction of 38,75% for ɣ-CD and 33,52% for ɣ-CDSI, compared to the uncomplexed ATZ. Thus, ATZ/ɣ-CD and ATZ/ɣ-CDSI have been proving to be more efficient and less toxic, probably due to the size of the internal cavity of ɣ-CD.