| Abstract
| - A controlled-release system with reduced environmental impact was produced by encapsulatingthe pesticide carbaryl in the waxy lipophilic material Gelucire 54/02. The microspheres were preparedby a modified hydrophobic congealable disperse-phase method. The influence of experimentalparameters, such as the reciprocal ratio between the amounts of pesticide and wax employed, onsize, morphology, loading efficiency, and release behavior of the particles was evaluated. Microsphereswere free-flowing and showed a nonporous scaly surface at SEM analysis. The mean particle sizeranged from 15.8 to 19.8 μm and was independent of the amount of Gelucire used to prepare themicrospheres. At a fixed Gelucire content, the increase in theoretical carbaryl content yielded up to72% loading efficiency, whereas at a fixed carbaryl content the increase in Gelucire amount produceda 64% increase in encapsulation efficiency. These data were accounted for by the carbaryl leakagefrom molten Gelucire toward the dispersing aqueous phase. The release profiles of carbaryl frommicrospheres showed that the use of increasing amounts of waxy material decreased the carbarylrelease rate, whereas at a fixed Gelucire content, the release was the slowest when carbaryl wasnot completely dissolved within the matrix. The possibility to achieve different burst effects by simplyvarying the formulation parameters offers an efficient tool to ensure the fast release of an activedose of insecticide. The lower vertical mobility of carbaryl encapsulated in waxy microspherescompared to the vertical mobility of the technical-grade product showed that the controlled-releasesystem has a lower potential risk for groundwater contamination. Keywords: Microspheres; wax; carbaryl; pesticides; environmental impact
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