Four-way modeling of 4.2K time-resolved excitation emission fluorescence data for the quantitation of Benzo[ a]pyrene and its metabolites in urine samples
Agustina Violeta Schenone
University of Central Florida
Humans are exposed to polycyc\ic aromatic hydrocarbons (PAHs) from various occupational, environmental, medicinal and dietary sources. The measurement of specific PAH metabolites has been extensively used as a means of assessing exposure to PAHs. There is considerable evidence that PAH are enzymaticalIy converted to reactive metabolites that bind covalently to celIular macromolecules, such as DNA, and this is considered to be an important step in tumor initiation by these carcinogens. A high level benzo[a]pyrene (B[a]P) metabolites in the urine would suggest a substantial exposure to PAHs. The existence of chemically related metabolic products with virtualIy identical fragmentation pattems oftenchallenges the specificity of the techniques used for their identification and quantification. The issue ofselectivity becomes even more crucial when facing a distribution of stereo-isomeric metabolites. In the present work, we will focus on B[a]P metabolites with mutagenic or carcinogenic relevance. B[a]P isthe most carcinogenic ofthe sixteen PAHs incJuded in the priority polIutants list ofthe US EnvironmentalProtection Agency (EPA). The new method is based on the colIection of 4.2K fluorescence time-resolved excitation-emission cubes (TREECs) via laser-excited time-resolved Shpol'skii spectroscopy with the aid of a cryogenic fiber opticprobe. 4.2K fluorescence TREECs result from the superposition of fluorescence time-resolved excitationemission matrices recorded at different time windows from the laser excitation pulse. For this purpose, a seriesof primary alcohols will be test as solvent host in order to improve the solubility of PAH metabolites in frozen matrix. The ability to directly determine the presence and the amounts oftargeted metabolites without the need ofextensive sample preparation and/or chromatographic separation, even if c\osely related stereo-isomers wouldbe our goal. Potential interference from unknown sample concomitants is handled by processing the four-way 4.2K fluorescence TREEC data arrays with either parallel factor analysis (PARAF AC) or unfolded partialleastsquares/residual-trilinearization (U-PLS/RTL) .