Controlled-release formulations of cyromazine-lignin matrix coated with ethylcellulose.
An encapsulation system was developed and designed to give long-lasting effectiveness of the insect growth regulator cyromazine. Cyromazine was incorporated in lignin-poly (ethylene glycol) (PE) controlled-release formulations by means of a melting process. The basic formulation [lignin (65%)-PE (20%)-cyromazine (15%)] was coated in a Wurster-type fluidized-bed equipment using two different amounts of ethylcellulose. That of the highest one was modified by the addition of a plasticizer, dibutyl sebacate (DBS). The effect on cyromazine release rate caused by the incorporation of ethylcellulose and DBS in lignin-PE formulation was studied by immersion of the granules in water under static conditions. Using an empirical equation, the time taken for 50% of the active ingredient to be released into water (T(50)) was calculated. From the analysis of the T(50) values, the influence of ethylcellulose appears clearly defined, observing a delay in release rate of cyromazine with respect to the basic lignin-PE formulation. In addition, the granules coated with ethylcellulose and the plasticizer lead the slowest release rate into water. The release of cyromazine into water is controlled by a diffusion mechanism. The thickness and permeability of the coating film are the most important factors that affect cyromazine release.
Fernández-Pérez
M
M
Department of Inorganic Chemistry, University of Almería, Almería, Spain. mfernand@ual.es
Villafranca-Sánchez
M
M
Flores-Céspedes
F
F
D000327:Adsorption; D002214:Capsules; D002482:Cellulose; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003692:Delayed-Action Preparations / Q000737:chemistry; D007605:Juvenile Hormones / Q000737:chemistry*; D008031:Lignin / Q000737:chemistry*; D014227:Triazines / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry
D002214:Capsules; D003692:Delayed-Action Preparations; D007605:Juvenile Hormones; D014227:Triazines; D014874:Water Pollutants, Chemical; D014867:Water; D002482:Cellulose; D008031:Lignin; C028704:cyromazine