Capillary zone electrophoresis (CZE) was used to determine the pKavalues of six environmentally and metabolically important PAH metabolites. The pKavalues obtained from CZE were close to the pKavalues reported in the literature which were obtained by spectroscopy. In this work, it was found that CZE is very suitable for the determination of the pKavalues of the weakly acidic, large ring PAH metabolites. A pKavalue acquired for one of the model compounds by spectrometry gave supporting evidence for the reliability of CZE in obtaining pKavalues for relatively large molecular weight hydroxyl compounds.