Time-Resolved Fluorescence in Micellar Systems:  A Critical Application to the Partitioning of Naphthalene in Aqueous Sodium Dodecyl Sulfate

Abstract

Static and dynamic aspects of the partitioning of naphthalene into the hydrocarbon phase in aqueous sodium dodecyl sulfate micelles have been critically examined by nanosecond time-resolved pulse fluorometry. It is shown that, in such a system, a properly detailed analysis of the excited-state decay behavior as a function of progressive partitioning of the solute into increasing concentrations of micelles is capable of revealing and directly quantitating the underlying kinetics of the reversible transfer of naphthalene in its excited state between aqueous and micellar phases. The time-resolved data indicate that, in the aqueous sodium dodecyl sulfate system, the partition coefficient for excited-state naphthalene can differ only marginally from that for the ground state. From the estimate obtained for the rate coefficient for entry of excited-state naphthalene into micelles, it would appear that any barrier to the crossing of excited naphthalene into the micelle, given that a collision has taken place, is likely to be rather small. The contrasting time-resolved behavior of a system in which the basis lifetime of the fluorescence probe in the micellar environment is shorter than that in the bulk environment rather than longer, as in the case examined experimentally, is also modeled. The effects of quenching of the fluorescence at the interface between the micellar and aqueous phases are also examined and discussed in the context of the aqueous cetyltrimethylammonium bromide system.

Modeling of anti-Langmuirian peaks in micellar electrokinetic chromatography: Benzene and naphthalene

“…agree well with previous determinations [2][3][4][5][6][36][37][38][39][40][41][42][43][44][45][46][47], although the different unit conventions must be considered. The inset to Fig.…”

“…The partition coefficients of the aromatic compounds, benzene (bz) and naphthalene (np), increase in SDS with increasing compound concentration, as evidenced by measurement of the micellar isotherm [2,3] or values at a few concentrations [4][5][6]. In this paper, we report measurements of these compounds' concave upward isotherms and predict from them and the continuity equation the peak profiles expected in MEKC.…”

Solubilization kinetics for polycyclic aromatic hydrocarbons transferring from a non-aqueous phase liquid to non-ionic surfactant solutions

“…Micelle water partitioning of hydrocarbons occurs in the order of a microsecond, and thus the adsorption of PAHs from the aqueous solution onto the micelles is not considered a ratelimiting process in the mass transfer [39,40].…”

Effects of Rhamnolipid Biosurfactants on Removal of Phenanthrene from Soil

“…Micellar partitioning reduces sorption of HOC to soil through reducing C HOC,aq (eqs 1−3). Partitioning of compounds from the water phase into surfactant micelles is generally considered an extremely fast process ( , ).…”