A membrane separator for orientation independent gas liquid separation in portable direct methanol fuel cell systems is presented in this paper. Its working principle is based on capillary forces using a combination of hydrophilic and hydrophobic materials with milli/micro structured channels. The efficiency of liquid recycling is studied experimentally with regard to the influence of system parameters and environmental parameters and to the separator's orientation. In further experiments, the limits for a complete gas separation are detected with respect to the volume flow of the gas and the liquid phase. It is shown that the orientation has only a minor influence on the liquid recycling efficiency compared to other parameters. Significant for the loss of liquid in the separator is the temperature difference between the inlet of the gas liquid stream and the environment. Furthermore, geometry parameters affect the limitation for the separation efficiency as well as system parameters. (C) 2011 Elsevier B.V. All rights reserved.