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.

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Applications

SFC finds use in industry primarily for separation of chiral molecules, and uses the same columns as standard HPLC systems. Achiral molecules are more difficult to separate via SFC.

Apparatus

SFC metering pumps require that the pump head 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 sets mobile phase flow rate, composition, and column temperature. In addition, SFC provides an additional control parameter, pressure, which the chemist similarly sets through the keyboard. From an operational standpoint, SFC is as simple and robust as HPLC.

Similar to a HPLC system, SFC can use a variety of detection methods. Primarily UV detection is used which requires the analyte to possess a chromophore.

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 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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