Methods and compositions for modifying the surface of a polymeric substrate are provided. In the subject methods, at least a portion of the surface of the polymeric substrate is contacted with a biofouling resistant surfactant composition. At least a portion of the surfactant molecules of the composition are end modified with a non-reactive, charged end group that is charge stable over a pH range of about 2 to 12. The subject methods and compositions find particular use with electrophoretic devices, such as capillary electrophoretic devices.