title: Evaluation of proton activity in microemulsions by a kinetic probe.
abstract: The decomposition reaction of the purple dye murexide in acidic media is used as a probe indicator for protons in nonionic microemulsions. The reaction kinetics primarily rely on the proton concentration and permit assessment of the proton activity in the nonionic microemulsions of water/cyclohexane/Igepal and water/heptane/Igepal. The experiments performed in the two microemulsions covered a wide range of water-to-oil mass fraction for the two systems. The kinetic runs were monitored under pseudo-first order conditions by the stopped-flow technique. The equilibrium constants for the formation of purpuric acid and the kinetic constants for the ensuing decomposition reaction fulfill a trend consistent with the micro compartmentalized nature of the multicomponent medium, and support the use of murexide as an indicator of the proton activity in microemulsions.
authors.affiliation: Universidad de Burgos, Departamento de Química, 09001 Burgos, Spain.
authors.forename: Indalecio A
authors.initials: IA
authors.lastname: Peñacoba
authors.forename: Begoña
authors.initials: B
authors.lastname: García
authors.forename: Ana M
authors.initials: AM
authors.lastname: Navarro
authors.forename: F Javier
authors.initials: FJ
authors.lastname: Hoyuelos
authors.forename: José M
authors.initials: JM
authors.lastname: Leal
mesh_terms: D004396:Coloring Agents / Q000737:chemistry*; D003510:Cyclohexanes / Q000737:chemistry; D004655:Emulsions / Q000737:chemistry; D006536:Heptanes / Q000737:chemistry; D007700:Kinetics; D009114:Murexide / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry; D011522:Protons; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D004396:Coloring Agents; D003510:Cyclohexanes; D004655:Emulsions; D006536:Heptanes; D011522:Protons; D013501:Surface-Active Agents; D014867:Water; D011092:Polyethylene Glycols; C506365:Cyclohexane; D009114:Murexide