Automatic separation of a two-phase mixture without separation funnel. Two-phase mixtures are completely applied to the column and the phase boundary is determined without further work. The special membrane automatically stops the flow when the lower phase has passed. The upper phase remains in the column, thus both phases are available for futher analysis. Columns must not be run with vacuum or pressure. PTL for solvents lighter than water, e.g., for diethyl ether, hexane.