title: The relationship between surface adsorption and the hydrolysis of amitraz in anionic surfactant solutions.
abstract: The adsorption of amitraz to various adsorbents was studied in terms of the amount and rate of adsorption and the effect that adsorption had on the stability of amitraz in an aqueous environment. Adsorption results showed that in terms of their ability to adsorb amitraz from solution the adsorbents tested in this study can be ordered as follows: coarse carbon > cation exchange resin > or = anion exchange resin > fine carbon. Amitraz was not adsorbed on sand and potassium oxihumate. Adding sodium lauryl sulfate and potassium oxihumate to aqueous suspensions of suspended adsorbents containing adsorbed amitraz showed that both these anionic surfactants significantly increased the hydrolysis rate because the half-lives for amitraz was reduced from 27 days for a suspension to only 8 hours for amitraz adsorbed to a cation exchange resin and suspended in an aqueous buffer pH 5.8 containing 0.5% of the anionic surfactant sodium lauryl sulfate and 12 hours when 1% potassium oxihumate was added.
authors.affiliation: Department of Basic Pharmaceutical Sciences, School of Pharmacy, University of Louisiana at Monroe, Monroe, Louisiana, USA. devilliers@ulm.edu
authors.forename: Melgardt M
authors.initials: MM
authors.lastname: de Villiers
authors.forename: Charmaine M
authors.initials: CM
authors.lastname: van Eeden
authors.forename: Sarel F
authors.initials: SF
authors.lastname: Malan
authors.forename: Bharathi
authors.initials: B
authors.lastname: Devarakonda
authors.forename: Wilna
authors.initials: W
authors.lastname: Liebenberg
authors.forename: William M
authors.initials: WM
authors.lastname: Kolling
mesh_terms: D000327:Adsorption; D002626:Chemistry, Pharmaceutical; D002851:Chromatography, High Pressure Liquid; D004355:Drug Stability; D006868:Hydrolysis; D007306:Insecticides / Q000737:chemistry*; D007700:Kinetics; D013501:Surface-Active Agents / Q000737:chemistry*; D014052:Toluidines / Q000737:chemistry*
chemical_list: D007306:Insecticides; D013501:Surface-Active Agents; D014052:Toluidines; C014983:amitraz