Low-temperature time-resolved phosphorescence excitation emission matrices for the analysis of phenanthro-thiophenes in chromatographic fractions of complex environmental extracts
Sadia Arif, Maha Al-Tameemi, Walter B. Wilson, Stephen A. Wise, Fernando Barbosa Jr., Andres Campiglia
Polycyclic aromatic sulfur heterocycles (PASHs) are sulfur analogues of polycyclic aromatic hydrocarbons (PAHs) widely found in environmental samples exposed to oil contamination. Despite their potential carcinogenic and mutagenic properties, only few methodologies usually based on liquid and gas chromatographic separations, are available for their determination in contaminated samples. Popular detection schemes include ultraviolet and visible absorption spectroscopy, room-temperature fluorescence spectroscopy and mass spectrometry. Herein, we investigate the analytical potential of low-temperature photoluminescence spectroscopy for the analysis of seven phenanthrothiophenes with molecular mass 234 g/mol. The studied PASHs include Phenanthro[1,2-b]thiophene, Phenanthro[2,1-b]thiophene, Phenanthro[2,3-b]thiophene, Phenanthro[3,2-b]thiophene, Phenanthro[3,4-b]thiophene, Phenanthro[4,3-b]thiophene and Phenanthro[9,10-b]thiophene. Excitation and emission spectra recorded from n-alkane solutions at room temperature, 77 K and 4.2 K show phosphorescence emission from all the studied isomers at cryogenic temperatures. The analytical figures of merit obtained under steady state (fluorescence) and time-resolved (phosphorescence) conditions provide limits of detection at the parts-per-billion (ng mL−1) concentration levels. Processing 77 K and 4.2 K phosphorescence data with parallel factor analysis showed to be a robust approach to the determination of phenanthrothiophenes in complex fluorophore mixtures.