Supercritical fluid chromatography

Supercritical Fluid Chromatography (SFC) is a robust and easy-to-use form of normal phase chromatography ideally suited to the analysis and purification of low to moderate molecular weight, thermally labile molecules. It is especially suited to 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.

Applications
SFC finds use 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. doi:10.1016/j.chroma.2005.02.087 There are more than 20 presentations available at the non-profit web site of The Green Chemistry Group http://www.greenchemistrygroup.org

Apparatus
SFC utilizes CO2 pumps that require that the incoming CO2 and pump heads be kept cold in order to maintain the carbon dioxide in a liquid state where it can be effectively metered at some specified flow rate. The chemist uses software to set mobile phase flow rate, co-solvent composition, and column temperature. In addition, SFC provides an additional control parameter, pressure, by using an automated back pressure regulator. From an operational standpoint, SFC is as simple and robust as HPLC but fraction collection is more convenient because the primary mobile phase evaporates leaving only the analyte and a small volume of polar co-solvent.

Similar to an HPLC system, SFC can use a variety of detection methods including UV/VIS, mass spectrometry and evaporative light scattering. http://www.internationallabmate.com/articles.php?id=58&section=%201

Sample Preparation
Any molecule that will dissolve in methanol or a less polar solvent can be analysed using SFC, including polar solutes.

Mobile Phase
The mobile phase is composed of high pressure liquid or supercritical carbon dioxide, however modifiers are added which can be used to change the chromatography, these are typically alcohols like methanol, ethanol or iso-propanol. Other solvent such as Acetonitrile and Chloroform can be used as modifiers. The solvent limitations are system and column based.

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