Supercritical fluid chromatography with a slurry‐packed capillary column

A versatile system with a slurry‐packed capillary column was developed for supercritical fluid chromatography, which is capable of programming both inlet and outlet pressure independently, as well as using a restrictor to apply back pressure. This system revealed the relationships between pressure drop, flow rate, and linear velocity in pressure‐programmed supercritical fluid chromatography. In the restrictor system, both the pressure drop and the flow rate increased almost linearly with inlet pressure, while under conditions of constant pressure drop characteristic behavior was observed which depended on the density‐viscosity relationships of supercritical fluid. Resolution in the separation of polysiloxane oligomers was found to be increased by increasing the ratio of pressure drop to pressure‐programming rate, although the sensitivity decreased due to the increase in peak volume. The system controlling both inlet and outlet pressure has distinct advantages over the restrictor system controlling both inlet and outlet pressure has distinct advantages over the restrictor system in practical in practical operations.