Pd. Wentzell et al., Three-way analysis of fluorescence spectra of polycyclic aromatic hydrocarbons with quenching by nitromethane, ANALYT CHEM, 73(7), 2001, pp. 1408-1415
The application of trilinear decomposition (TLD) to the analysis of fluores
cence excitation-emission matrices of mixtures of polycyclic aromatic hydro
carbons (PAHs) is described. The variables constituting the third-order ten
ser are excitation wavelength, emission wavelength, and concentration of a
fluorescence quencher (nitromethane), The addition of a quencher to PAH mix
tures selectively reduces the fluorescence intensity of mixture components
according to the Stern-Volmer equation. TLD allows the three-way matrix to
be decomposed to give unique solutions for the excitation spectrum, emissio
n spectrum, and quenching pro files for each component. The availability of
spectra and calculated Stern-Volmer constants can aid in the identificatio
n of unknown components. Preprocessing of the data to correct for Rayleigh/
Raman scatter and primary absorption by the quencher is necessary. Both thr
ee-component (anthracene, pyrene, l-methylpyrene) and four-component (fluor
anthene, anthracene, pyrene, 2,3-benzofluorene) synthetic mixtures are succ
essfully resolved by TLD using quencher concentrations up to 100 mM, Result
s are compared using both alternating least-squares and direct trilinear de
composition algorithms. The reproducibility of extracted Stern-Volmer const
ants is determined from replicate experiments. To illustrate the applicatio
n of TLD to a real sample, a chromatographic cut from the analysis of a lig
ht gas oil sample was used. Analysis of the TLD extracted spectra and quenc
hing constants suggests the presence of three classes of polycyclic aromati
c hydrocarbons consistent with data from a second dimension of chromatograp
hy and mass spectrometry.