Countercurrent Chromatography - Chromatography

Chromatography

Chromatography in general is used to separate components of a mixture based on their differing affinities for mobile and stationary phases of a column. The components can then be analyzed separately by various sorts of detectors which may or may not be integrated into an apparatus. Partition chromatography is based on differences in capacity factor, k, and distribution coefficient, Kd, of the analytes using liquid stationary and mobile liquid phase. An analyte is the substance or chemical constituent that is being analyzed.

Standard column chromatography uses a solid stationary phase and a liquid mobile phase, while gas chromatography (GC) uses a liquid stationary phase on a solid support and a gaseous mobile phase. By contrast, in liquid-liquid chromatography, both the mobile and stationary phases are liquid.

By eliminating solid supports, permanent adsorption of the analyte onto the column is avoided, and a near 100% recovery of the analyte can be achieved. The instrument is also easily switched between various modes of operation simply by changing solvents. With liquid-liquid chromatography, researchers are not limited by the composition of the columns commercially available for their instrument. Nearly any pair of immiscible solutions can be used in liquid-liquid chromatography, and most instruments can be operated in standard or reverse-phase modes.

Solvent costs are also generally cheaper than for High-performance liquid chromatography (HPLC), and the cost of purchasing and disposing of solid adsorbents is completely eliminated. Another advantage is that experiments conducted in the laboratory can easily be scaled to industrial volumes. When GC or HPLC is carried out with large volumes, resolution is lost due to issues with surface-to-volume ratios and flow dynamics; this is avoided when both phases are liquid.