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

Abstract

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.

Application of PARAFAC to a two-component system exhibiting Fluorescence Resonance Energy Transfer: from theoretical prediction to experimental validation

“…Another issue worth noting is that determining the ''similarity'' between two components' spectra can be difficult; for example, in a recent paper we found that the spectra of solutes (biphenyl or 2,5-diphenyloxazole (PPO)) in water phase and in micelle phase of sodium dodecyl sulfate were quite similar but not identical. 17 Because of the polarity difference in the two phases, the spectra in the two phases are not strictly identical. The very similar spectra in the two phases would be falsely forced to be identical when applying PARALIND in the absence of a priori knowledge.…”

Linking fluorescence spectroscopy to diffuse soil source for dissolved humic substances in the Daning River, China

“…Excitation light intensity incident on the uorescence cuvette as a function of lamp output wavelength, and uorescence detector sensitivity as a function of uorescence wavelength, were both corrected as recommended by the uorometer user's manual. The scattering light signals in the EEMs were eliminated from the analysis according to an approach employed previously, 7,27,28 which consisted in replacing the data region containing scattering light signals with "NaN" (not a number) using a home-written program implemented in a Matlab 6.5 soware package (Mathworks, Natick, US). The UV-Vis absorbance at wavelengths of 250 through 600 nm with 1 nm intervals was measured in 1 cm quartz cuvettes on a Shimadzu 1700 spectrophotometer in double-beam mode.…”

“…30 This method has proven efficient in IFE correction for uorescence data in previous PARAFAC studies. 25,27,31,32 The concentrations of DOC were determined by high temperature combustion on a Shimadzu TOC-VCPH instrument with a detection limit of 0.06 mg L À1 . A non-purgeable DOC measurement mode was employed, in which the sample was acidied to pH 2 by aliquots of concentrated HCl and then purged with high purity (>99.995%) oxygen gas to remove inorganic carbon before determination of DOC concentration.…”

“…31 Fluorescence intensities at peak excitation/emission wavelength pairs of a given component, referred to as F max , were computed according to the component's spectral features (loading) and relative abundance (score) reported by PARAFAC models. 27 Following Stedmon et al, 38 F max was divided by the integrated under-peak intensity of the Raman bands of pure water generated by an excitation of 350 nm on the same uorometer as for EEMs measurements, and was reported in Raman units (nm À1 ) in this study.…”

Comparison of PARAFAC and PARALIND in modeling three‐way fluorescence data array with special linear dependences in three modes: a case study in 2‐naphthol

“…To avoid light scattering problems, the EEMs of blank water were extracted from the data EEMs, and fluorescence intensities at emission wavelength not far different than excitation wavelength (wavelength difference less than 10 nm) were set to NaN (not‐a‐number, a variable that can be handled by Matlab) to refer to missing data. The use of missing data to replace scattering light in EEMs has been successfully implemented in previous studies 3, 16–18. Based on the formula derived by MacDonald et al .…”