Application of PARAFAC to determination of distribution constants and spectra of fluorescent solutes in micellar solutions.

Steady state fluorescence excitation emission matrices (EEMs) and time-resolved fluorescence of biphenyl (BP) and 2,5-diphenyloxazole (PPO) dissolved in aqueous solutions of sodium dodecyl sulfate (SDS) were measured as a function of micelle concentration. Parallel factor analysis (PARAFAC) was applied for the first time to the determination of the distribution of solutes between the bulk aqueous phase and the SDS micellar phase, as well as their excitation and emission spectra in both phases. The raw scores of the PARAFAC analysis, which contain concentration information, are also dependent on photophysical parameters which can change upon micellization of the solute; we have developed a method of isolating accurate concentration values from the scores. The distribution constant of PPO, previously unreported, was found to be (8.8 +/- 0.7) x 10(5) M(-1), while the distribution constant of BP, for which various values have been reported, was found to be (4.5 +/- 0.2) x 10(4) M(-1). BP and PPO both showed weakly phase-dependent excitation and emission spectra. The method was validated by determining distribution constants for anthracene, phenanthrene, naphthalene, and pyrene, all of which showed good agreement with consensus values available in the literature.