Which term in the Van Deemter equation is affected by the following changes and would plate...

Which term in the Van Deemter equation is affected by the following changes and would plate height increase or decrease? Explain your reasoning.

(a) Changing the mobile phase from a gas to a supercritical fluid

(b) Changing the stationary phase thickness in a wall coated open tubular GC column from 5µm to 0.5µm.

Expert Solution

a) Supercritical Fluid Chromatography (SFC) is a form of normal phase chromatography, first used in 1962, that is used for the analysis and purification of low to moderatemolecular weight, thermally labile molecules. It can also be used for the separation of chiral compounds. Principles are similar to those of high performance liquid chromatography (HPLC), however SFC typically utilizes carbon dioxide as the mobile phase; therefore the entire chromatographic flow path must be pressurized. Because the supercritical phase represents a state in which liquid and gas properties converge, supercritical fluid chromatography is sometimes called "convergence chromatography." SFC is used in industry primarily for separation of chiral molecules, and uses the same columns as standard HPLC systems. SFC is now commonly used for achiral separations and purifications in the pharmaceutical industry.

queen_honey_blossom answered 2 years ago

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