The effect of α-amylases upon the release of trifluralin encapsulated in starch

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Abstract

Release of trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine] encapsulated in starch was induced by water and starch-degrading α-amylases. Factors investigated that influenced the rate of release are: encapsulation procedure, particle size of the encapsulated material, and pH of the medium. Variations within a procedure such as additional covalent crosslinking, starch retrogradation, and inclusion of enzyme inhibitors can affect the rate of release. For the three basic encapsulation methods used (xanthide, calcium, or borate), the rate of release was borate > calcium > xanthide when the particles were placed in pH 6.0 buffer. Coarse fractions (4–8 mesh) released trifluralin at less than one-fifth the rate of fine fractions (20–40 mesh). Release rates varied little upon varying the source of the α-amylase or the level of active ingredient (4–20%) within the particles. Trifluralin release from particles prepared by the borate procedure was slowed by crosslinking of the starch matrix with epichlorohydrin and by addition of heavy metal ions. The ability to detect variations in the rate of release as a function of these variables can serve as a basis for producing starch-encapsulated herbicides for particular end uses.

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Presented at the 11th International Symposium on Controlled Release of Bioactive Materials, Fort Lauderdale, FL, July 22–25, 1984.

∗∗∗

This article reports the results of research only. Mention of a pesticide in this article does not constitute a recommendation for use by the U.S. Department of Agriculture nor does it imply registration under FIFRA as amended. The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.

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