Selectivity

The range of selectivities accessible by SFC is the same as for HPLC. This is not surprising since selectivity depends on the physical and chemical nature of the stationary and mobile phases. The stationary phases used in Prep-SFC are exactly the same as the ones used in Prep-HPLC. Theoretically, some stationary phases specific to SFC could be used (e.g. cross-linked polymers deposited on a silica support), but phases developed for HPLC are the only ones available in large quantities and, thus, they are the only ones used. Supercritical eluents are fewer in number than the mobile phases used in HPLC and, indeed, carbon dioxide is almost the only supercritical eluent used for Prep-SFC. But the possible use of modifiers, which can be almost any liquid solvent or any mixture, is a powerful parameter for variation of selectivity. Moreover, by changing the operating pressure it

is possible to adjust the solvent strength of the supercritical eluent, since it is compressible, without changing its composition.

The foregoing does not mean that there is no selectivity difference between the two techniques: for a given application, selectivity obtained by SFC can be much higher than by HPLC and vice versa.

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.

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