Passive sampling with PA fiber provided similar isotherms of cationic surfactants as direct sampling. Fouling with kaolinite particles and high isotherm nonlinearity at high concentrations may cause increased errors in PA fiber measurements. For kaolinite under the studied conditions, conventional centrifugation appeared to be effective in removing particles from suspension and may be more convenient than passive sampling for the compounds studied. Despite the limitations noted, passive sampling was useful in verifying the results of the conventional method in this study and could serve as an alternative method in other cases.