Evaluation of proton activity in microemulsions by a kinetic probe.

Indalecio A Peñacoba, Begoña García, Ana M Navarro, F Javier Hoyuelos, José M Leal, Indalecio A. Peñacoba, Begoña García, Ana M. Navarro, F. Javier Hoyuelos, José M. Leal

Index: J. Colloid. Interface Sci. 352(2) , 465-9, (2010)

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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.Copyright © 2010 Elsevier Inc. All rights reserved.