We report an automated procedure for the inline separation of two immiscible liquids based on a
porous polytetrafluoroethylene (PTFE) capillary and a small number of inexpensive electronic
components. By monitoring the light transmitted through fluid streams at the two outlets of the
separator and iteratively adjusting a needle-valve located at one outlet until smooth time-invariant
signals are observed at both outlets, the separator is capable of establishing complete liquid/liquid
separation within minutes. Using mixtures of water and toluene as a test system, near quantitative
recovery of the two liquids was achieved over a wide range of flow conditions without detectable cross
contamination at either outlet. In a twenty-four hour test run, departures from complete separation
occurred just three times, and on each occasion complete separation was automatically restored within
ninety seconds. Further tests on other liquid/liquid mixtures showed that the automated separator is
capable of rapidly and reliably inducing the separation of aqueous–organic, aqueous–fluorous and
organic–fluorous mixtures, making it a versatile tool for numerous applications in fluidic analysis,
synthesis and purification.