This study examined the isotherm of polycyclic aromatic hydrocarbons (PAHs) adsorbed on capillary concentrating tubing. Equations for common adsorption isotherms, including Langmuir and modified Freundlich, were used to fit the adsorption data obtained from pyrene and acenaphthene samples. Each fitting＇s correlation coefficient was then used to assess the appropriateness of the isotherm of interest. Experimental results indicate that the modified Frundlich isotherm most aptly accounts for monocomponent PAH adsorption from water onto ethyl vinyl acetate tubing. From the appropriateness of the Langmuir isotherm individually in low-and high-concentration ranges, multilayer adsorption apparently occurs at a higher concentration. In bicomponent adsorption, acenaphthene was highly competitive with pyrene at a higher competition coefficient. In addition, the competitive coefficient of an analyte increased with decreasing competitor concentration.