On the co-elution of benzo[ a ]pyrene and dibenzo[ a , l ]pyrene in chromatographic fractions and their unambiguous determination in tobacco extracts via laser-excited time resolved Shpol'skii spectroscopy.

High performance liquid chromatography is widely used for the analysis of polycyclic aromatic hydrocarbons in a wide variety of samples. Of particular concern are benzo[ a ]pyrene and dibenzo[ a , l ]pyrene, two of the most toxic polycyclic aromatic hydrocarbons ever tested. Under EPA method 610, these two compounds co-elute with almost identical retention times. Our studies demonstrate the feasibility of directly determining them in a chromatographic fraction without further separation. Their unambiguous determination is based on spectral and lifetime information with a two-step experimental procedure consisting of the evaporation of the chromatographic fraction followed by the dissolution of the residue with microliters of n -octane. With the aid of a 77 K fiber optic probe, limits of detection at the parts-per-billion concentration level (ng mL -1 ) are obtained from the microliter sample via laser excited time resolved Shpol'skii spectroscopy. This approach is then applied to the analysis of benzo[ a ]pyrene and dibenzo[ a , l ]pyrene in tobacco extracts.