High Pressure Trapping with Subsequent Recovery by Solidification of the Carbon Dioxide

11 High Pressure Trapping with Subsequent Recovery by Solidification of the Carbon Dioxide 

Initial collection of acetophenone and of various coloured dye tracers indicated that when using a stainless steel cylinder (10 mm x 250 mm, 20 mL volume) as the collection vessel the total volume of the cylinder was not available for the solute. The dye experiments indicated that about half the total volume was available for collection of the solute. The reasons for this are as follows. The Hagen-Poiseuille equation, which describes the velocity profile of a liquid flowing through a tube under laminar flow conditions predicts that the maximum velocity of the head of the parabolic flow profile will be twice the mean velocity of the liquid [23]. Breakthrough of the dye tracer would therefore be expected in about half the volume of the tube. Fluid mechanics predicts that if the flow is turbulent the difference between the mean and maximum flow velocities is much less than in laminar flow [23]. This means that un- 

8 Scaling-up of Supercritical Fluid Chromatography to Large-Scale Applications 

A version of the baffled collection vessel was fabricated from stainless steel for use at high pressure. This vessel is pictured in Fig. 8-12 and its construction detailed by Fig. 8-13. The sample collection vessel has been constructed to withstand a working pressure of up to 400 Bar (6000 psi) and contain up to 60 cm of fluid. The internal baffle discs allow the vessel to fill up from the bottom without too much mixing in order that much of the available volume is used. 

---