A system for the retrieval and initial conditioning of sample gas for "on line" analyzers or filling of gas sample cylinders. The preferred embodiment of the present invention contemplates a system configured to obtain a representative gas phase sample from a process gas containing entrained liquid, or a process gas which generally is highly susceptible to partial condensation of some gas phase components. The preferred embodiment of the present invention teaches an assembly including a phase separation membrane and housing configured to facilitate the removal of entrained liquid from a sample gas stream. Accuracy of the sample is enhanced, and compositional changes are avoided by first extracting a sample from the process gas followed by removal of entrained liquid it may contain, with the entrained liquid removal being conducted at the prevailing process gas pressure and temperature. Thereafter the liquid free sample may be desaturated by lowering its pressure to reduce its susceptibility to condensation.