The pervaporation performance of polyethersulfone (PES) membranes prepared by incorporating surface modifying macromolecules (SMMs) was evaluated via experiments with chloroform/water mixtures as the feed. Isolation and chemical analysis of the organics in the permeate revealed that the permeate contained virtually no chloroform. The bulk of the isolated organic compounds was ethanol. This differed from previous reports, which claimed that the organic component isolated via gas chromatographic analysis was chloroform (Y. Fang et al., Journal of Applied Polymer Science, 1994, Vol. 54, pp. 1934-1943; Y. Fang et al., in Proceedings of the Seventh International Conference on Pervaporation. Processes in the Chemical Industry, R. A. Bakish, Ed., Bakish Materials Corporation: Englewood, NJ, 1995, pp 349-362). It was demonstrated that ethanol, used during the solvent exchange drying step of membrane preparation, was retained in the membrane and leached out during membrane use. However, while it was observed that SMMs in PES membranes contributed to no enrichment of chloroform, there was a significant depletion of chloroform achieved in the permeate. The increased separation of chloroform from the SMM-modified membranes is hypothesized to be related to the unique fluorinated surface character endorsed within the material by the novel modification process.