Plate height supercritical fluid

D. P. Poe and D. E. Marthe, Plate height theory for compressible mobile phase fluids and its application to gas, liquid and supercritical fluid cliromatography , 7. Chromatogr. 517 3-29(1990). 

Capillary supercritical fluid chromatography (SFC) columns are 0.1-0.025 mm ID and 3-20 m in length. Good reviews of the technique of SFC have been recently published [52-55]. It was reported that the optimum inner diameter for capillary SFC based on plate height, linear velocity, analysis time, and column length was around 0.050 mm. 

Figure 33-2 shows plots of plate heights // as a function of average linear velocity u in cm/s for high-performance liquid chromatography and supercritical-fluid chromatography. In both cases, the solute was pyrene, and the stationary phase was a reversed-phase octadecyl silane maintained at 40°C. The mobile phase for HPLC was acetonitrile and water, while for SFC the mobile phase was carbon dioxide. These conditions yielded about the same retention factor (k) for both mobile phases. Note that the minimum in plate height occurred at a flow rate of 0.13 cm/s... 

Figure 3. Calculated height equivalent to a theoretical plate, h, vs. log of the mobile phase velocity for a perfect analyte eluted on one capillary column with three different mobile phases. Assumptions are column inside diameter is 50 urn diffusion coefficients are 10 1 cm2/s for gas, 10-3 and 10-A cm2/s for low-and high-density supercritical fluid, respectively, and 10 cm /s for liquid.

---