Isomer identification of monohydroxylated polycyclic aromatic hydrocarbon metabolites by gas chromatography/fourier transform infrared spectroscopy and carbon-13 nuclear magnetic resonance spectroscopy

The foundation for a systematic approach utilizing spectral/structural correlations was established for unambiguous identification of monohydroxylated polyaromatic hydrocarbon metabolite (PAHm) isomers. Using elements of a theoretical/empirical valence-bond model developed earlier in our laboratory for isomer identification of chlorinated dibenzo-p-dioxin isomers, both gas chromatography/Fourier transform infrared spectroscopy (GC/FTIR) and carbon-13 nuclear magnetic resonance (¹³C NMR) spectroscopy were employed for PAHm isomer identification. Results indicate that PAHm isomers also can be systematically identified by these techniques. However, many of the parameters leading to the success of the dioxin analysis (high symmetry of the parent dioxin molecule and laterally stabilized delocalization from chlorine substituents through ether linkage oxonium ions) are not generally present in the PAHm ring systems under investigation. The observed infrared parameters in PAH metabolites are C-O stretch, O-H stretching and bending vibrations, along with C=C skeletal stretching vibrations. In addition, ¹³C NMR parameters such as chemical shift perturbations for carbons adjacent to functional groups have been observed.