Cyclodextrin-aided Capillary Electrophoretic Separation and Laser-induced Fluorescence Detection of Polynuclear Aromatic Hydrocarbons (PAHs)

Two neutral cyclodextrins (CDs), hydroxypropyl-β-CD (HPβOD) and methyl-β-CD (MβCD), and two negatively charged forms, carboxymethyl-β-CD (CMβCD) and sulfobutylether-β-CD (SBβCD), were used to demonstrate the principle of separation of hydrophobic and non-charged polynuclear aromatic hydrocarbons (PAHs) by capillary electrophoresis (CE) based on differential partitioning of analytes between the CDs. The estimation of the partition coefficient (K_i) confirmed that the PAH components which partitioned most to the negative cyclodextrin (i.e. with the highest K_i) exhibited the longest migration time. The K_i values obtained for the CMβCD-HPβCD system are all below 1, indicating that the PAHs prefer to remain in the neutral HPβCD. The K_i values for the SBβCD-MβCD buffer are all greater than 1, and cover a wider range, indicating preference of the PAHs for the anionic derivative. Methods were applied for separation of a PAH mixture containing various important PAHs on the US Environmental Protection Agency priority list. This novel procedure provided much better separation of PAH isomers, including benzo[a]pyrene and benzo[e]pyrene, than has been reported previously using CE. The system was applied to the sensitive determination of nanomolar levels of PAHs in contaminated soil.