ASSESSMENT OF CHITOSAN GELS FOR THE CONTROLLED RELEASE OF AGROCHEMICALS

Chitosan gel beads and films were assessed for their ability to control the release of the herbicide atrazine and the fertilizer urea. The gel beads and films, containing entrapped agrochemicals, were prepared by reacting solutions of chitosan with acetic or propionic anhydride. Elution studies conducted on chitosan-coated atrazine beads showed an initial rapid release of atrazine followed by a constant release rate. The chitosan gel beads were estimated to be able to extend the release period of atrazine to 7 months compared to 4 days for uncoated control beads. Elution studies performed on chitosan-coated urea beads showed that it was possible to extend the duration of action of urea release by a factor of up to 180 compared to uncoated urea control beads. Entrapment of atrazine beads in N-propionylchitosan films was found to be the most suitable method for controlling the release rate of the herbicide at about 1% / day. Both gel beads and films retained approximately 50% w/w water. © 1990, American Chemical Society. All rights reserved.