ALGINATE CONTROLLED RELEASE FORMULATIONS OF METRIBUZIN

The release rates of metribuzin from various alginate-clay formulations were investigated. The standard formulation consisted of 1% alginate-1% metribuzin congruent-to 10% clay and 88% water. The type of alginate was found to have little effect on release rate but did affect the physical properties of both the slurry and the dried beads. The replacement of clay with adsorbents for organic compounds (4% adsorbent-6% clay) indicated no advantage for alumina, silica gel, and Celite. With charcoal, a slow down of release was observed but some metribuzin was irreversibly adsorbed. If a ratio of 1% charcoal-9% clay was used, then the rate of release was slowed and only 8% of the metribuzin was irreversibly adsorbed. The adsorbent formulations had phytotoxicity comparable to commercial formulations of metribuzin.