Efficiency and Speed

Prep-SFC can attain efficiencies as good as those for Prep-HPLC. A reduction in plate heights of a factor of between two and four are easily obtained leading to efficiencies of between 10000 and 70000 plates per metre depending on particle size. Moreover, Prep-SFC has, just like analytical SFC, the advantage of being able to combine high efficiencies with high speed. Indeed, as can be seen in Figure 2, in any type of chromatography, a plate height increase (corresponding to a loss of efficiency) is observed when the eluent speed is increased beyond the minimum point. The slope of the curve is correlated to the diffusion coefficient of the sample in the eluent (the higher the diffusivity the smaller the slope). Since diffusion coefficients of supercritical fluids are much smaller than in liquids, the curve is flatter and it is possible to increase the eluent speed (and the productivity) without losing much efficiency. Moreover, in HPLC eluent speed is limited by the pressure drop in the column while in SFC the viscosity of the eluent is much less and such a limitation does not apply. To obtain high efficiencies in large diameter columns, the same difficulties are encountered in Prep-SFC as in Prep-HPLC. For diameters over 5 cm prepacked columns are not

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

Get My Free Ebook


Post a comment