Liquid–liquid–liquid microextraction for the enrichment of polycyclic aromatic hydrocarbon metabolites investigated with fluorescence spectroscopy and capillary electrophoresis Original Research Article

The extraction and pre-concentration of phenol, 2-naphthol, and several hydroxyl polycyclic aromatic hydrocarbon (PAH) metabolites were investigated, using liquid–liquid–liquid microextraction (LLLME). The PAH metabolites are a very important class of compounds, and they have not been investigated previously by LLLME. For several of the hydroxyl PAH metabolites, the enrichment factors were small when using LLLME with an alkaline acceptor phase. Changing the acceptor phase to 1-octanol, which gave a two-phase system, improved the enrichment factors significantly for several of the hydroxyl PAH metabolites. For example, the enrichment factor was improved by a factor of 68.5 for 3-hydroxybenzo[a]pyrene. Enrichment factors were investigated as a function of time and stirring rate. At about 55 min the enrichment factor reached a maximum for the two-phase system and at approximately 75 min for the three-phase microextraction system. However, a 30 min extraction time was used for most of the experiments. Also, fluorescence spectroscopy was used to determine the enrichment factors and the mass distribution of the solute between the phases. Fluorescence spectroscopy was very effective in determining the very small concentrations of the solute in the various phases. In addition, capillary electrophoresis and LLLME were combined to demonstrate the substantial enrichment of 2-naphthol by combining these two approaches.