title: Controlled release formulations of metribuzin: release kinetics in water and soil.
abstract: Controlled release (CR) formulations of metribuzin in Polyvinyl chloride [(PVC) (emulsion)], carboxy methyl cellulose (CMC), and carboxy methyl cellulose-kaolinite composite (CMC-KAO), are reported. Kinetics of its release in water and soil was studied in comparison with the commercial formulation (75 DF). Metribuzin from the commercial formulation became non-detectable after 35 days whereas it attained maxima between 35-49 days and became non-detectable after 63 days in the developed products. Amongst the CR formulations, the release in both water and soil was the fastest in CMC and slowest in PVC. The CMC-KAO composite reduced the rate of release as compared to CMC alone. The diffusion exponent (n value) of metribuzin in water and soil ranged from 0.515 to 0.745 and 0.662 to 1.296, respectively in the various formulations. The release was diffusion controlled with half release time (t(1/2)) from different controlled release matrices of 12.98 to 47.63 days in water and 16.90 to 51.79 days in soil. It was 3.25 and 4.66 days, respectively in the commercial formulation. The period of optimum availability of metribuzin in water and soil from controlled released formulations ranged from 15.09 to 31.68 and 17.99 to 34.72 days as against 5.03 and 8.80 days in the commercial formulation.
authors.affiliation: Division of Agricultural Chemicals, Indian Agricultural Research Institute, New Delhi, India. jitendrakumar7@yahoo.com
authors.forename: Jitendra
authors.initials: J
authors.lastname: Kumar
authors.forename: Keyath
authors.initials: K
authors.lastname: Nisar
authors.forename: N A
authors.initials: NA
authors.lastname: Shakil
authors.forename: Suresh
authors.initials: S
authors.lastname: Walia
authors.forename: Rajender
authors.initials: R
authors.lastname: Parsad
mesh_terms: D002266:Carboxymethylcellulose Sodium / Q000737:chemistry; D003692:Delayed-Action Preparations / Q000737:chemistry*; D004058:Diffusion; D004655:Emulsions; D006540:Herbicides / Q000032:analysis / Q000737:chemistry; D007616:Kaolin / Q000737:chemistry; D007700:Kinetics; D011143:Polyvinyl Chloride / Q000737:chemistry; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry; D012995:Solubility; D014227:Triazines / Q000032:analysis* / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D003692:Delayed-Action Preparations; D004655:Emulsions; D006540:Herbicides; D012987:Soil; D012989:Soil Pollutants; D014227:Triazines; D014867:Water; D007616:Kaolin; D011143:Polyvinyl Chloride; D002266:Carboxymethylcellulose Sodium; C009235:metribuzin