Ultrasensitive Fluorescence Detection of Polycyclic Aromatic Hydrocarbons in Capillary Electrophoresis

Capillary electrophoresis with UV-laser-excited native fluorescence has been employed for ultrasensitive determination of polycyclic aromatic hydrocarbons, including anthracene, phenanthrene, benz[a]anthracene, methylanthracene, pyrene, fluoranthene, and perylene. The separation is based on solvophobic association of the analytes with tetraalkylammonium ions in mixed acetonitrile/water solvent. With both near-UV (325-nm) and deep-UV (257-nm) laser excitation, background fluorescence from the fused silica capillary and the nonaqueous electrolyte was the limiting factor in detection sensitivity. Effective rejection of the intense capillary wall fluorescence was achieved by the use of a high-numericalaperture microscope objective coupled with an adjustable precision slit in a confocal configuration. The achieved mass detection limits were in the range of (3-15) × 10^-20 mol, with linear fluorescence response spanning over 4 orders of magnitude. This sensitivity is expected to be sufficient for analyzing chemical carcinogens, anticancer drugs, and their metabolites in individual mammalian cells.