Fig. 3.
(A) Schematic diagram of typical GC-like open tubular column SFC system. Since the flow rate is very low, a screw-driven syringe pump is used. Backpressure is applied by a restrictor that has a certain flow resistance to keep the system pressure above the critical pressure of the fluid. Pressure was controlled by changing the mobile phase flow rate. (B) Schematic diagram of typical LC-like packed-column SFC system with automated backpressure regulator. PU1: liquefied CO2 delivery reciprocating pump with chilled pump heads; PU2: modifier solvent delivery pump; RF: safety relief valve that prevents over pressure; INJ: injection valve; PDA: photodiode array UV detector; PT: pressure transducer; and BR: backpressure regulator. The pressure transducer monitors the pressure real time and the backpressure regulator compares the set pressure and actual pressure and control the flow resistance of the regulator so that the actual pressure becomes equal to the set pressure. Reproduced from reference [1], with the permission of Elsevier.