A simple phase separator consisting of a hydrophobic T-connector and a hydrophilic needle was developed for microfluidic extraction studies. The phase separator based on the selective wettability of fluids has a very small volume and nearly zero hold-up of the continuous phase. It is easy to assemble, clean and repair in the laboratory. Four classical extraction systems with interfacial tensions ranging from 49.6 to 1.68 mN/m worked well in this phase separator over operating flow rates ranging from 150 and 1500 mu L/ min. Mass transfer experiments showed that the measured mass transfer coefficients from the new phase separator were more accurate than the data from the gravity phase separator. This phase separator has strong potential to be used in the kinetic study of mass transfer in tubular microfluidic device. (C) 2017 Elsevier B.V. All rights reserved.