Capillary column SFC instrumentation based on piston pumps with a programmable back-pressure regulator for on-line mixing of mobile phases

An alternative phase delivery system based on piston pumps and a back-pressure regulator has been developed for capillary column SFC. The chromatography is not affected by the fast piston pump refill. A homogeneous on-line mixing of binary phases with simultaneous pressure programming is easily accessible without any additional computing. Acceptable reproducibilities (< 3.5% RSD for external and < 2.0% RSD for internal standard methods) were found with mixtures of 2-propanol/CO₂ as mobile phases using UV detection and split ratios of 1:60 and 1:120. Variation and control of the split are easily done by simple flow rate volumetric changes.