Determination of polycyclic aromatic hydrocarbons in soil samples by micellar electrokinetic capillary chromatography with photodiode-array detection

Abstract

The reliable quantification even of trace amounts of polycyclic aromatic hydrocarbons (PAHs) is of great concern in environmental and also in medical analysis. PAHs are typically small, uncharged, hydrophobic molecules which do not dissolve well in water. Several methods were investigated and compared for the determination of such substances by capillary electrophoresis, including systems where the analytes are provided with a charge (tetraalkylammonium ions) via solvophobic interaction and systems based on micellar electrokinetic capillary electrophoresis (MECC) using sodium dodecyl sulphate (SDS) and cetyltrimethylammonium bromide as micelle-forming agents. Diode-array detection permitted the positive identification of the separated pure substances via their prerecorded UV-Vis spectra. By using an aqueous-organic electrophoresis buffer [8.5 m M borate, 85 m M SDS, 50% (v/v) acetonitrile, pH 9.9], a mixture of seven standard PAHs could be separated and quantified within 10 min. The detection limit was 10 pg. The calibration graph was linear over five orders of magnitude. Compared with the chromatographic analysis used so far, the MECC method is faster, has a higher mass sensitivity and requires a smaller sample volume. The method was used to quantify the PAH content of soil samples (heath sand) deliberately contaminated with a mixture of standard PAHs and with machine oil. Two PAHs (anthracene and chrysene) could be determined in samples collected during a biological soil decontamination process.