FRX systems consist of a number of separate modules which can be connected together for conducting different flow chemistry experiments. Reactions occur under controllable, laminar flow conditions. The systems are modular, allowing chemists to select the system that best meets their individual needs, and can be easily upgraded to meet changing demands. FRX systems range from the basic 100, designed for initial flow chemistry work using a large volume tube reactor, and the 200, with a micro-reactor and solid phase column, to the more complex 300 and 400 units for multi-step chemistry and sophisticated set ups. Both the FRX 300 and 400 incorporate an FRX Flow Liquid-Liquid EXtraction module (FLLEX). The FLLEX facilitates compound purification and separation post reaction, which once separated can be passed for collection, analysis or further reaction. In addition to small scale optimizations, the high end FRX 400 can also allow reaction cooling and be used with solid supported chemistries.