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Countercurrent chromatography (CCC) is a liquid chromatography technique that uses two immiscible liquid phases and no solid support. One liquid acts as the stationary phase and the other as the mobile phase. In Dual Flow CCC/CPC both liquid phases are flowing, as would be common in counter current process extractors. The liquid stationary phase(s) is held in place by gravity or by centrifugal force. The gravity method is called droplet counter current chromatography (DCCC). There are two modes of centrifugal force CCC: hydrostatic and hydrodynamic. In the hydrostatic method, the column is spun about a central axis. These devices are marketed under the commercial name centrifugal partition chromatography (CPC).〔〔 Dynamic mode is often called high-speed CCC (HSCCC) and relies on the Archimedes' screw force in a helical coil to produce the separation.〔 ==Support-free liquid chromatography== Standard column chromatography uses an apparent solid stationary phase and a liquid mobile phase, while gas chromatography (GC) uses a solid or 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. The contrast is, however not as stark as it first appears. In reverse phase HPLC, the phases, can in many cases be regarded as liquids which are immobilized by chemical bonding to a solid support, such as micro-porous silica. As opposed to CCC/CPC where mechanical/gravitational forces are used to achieve to stationary liquid layer instead of bonding to a solid support. By eliminating solid supports, permanent adsorption of the analyte onto the column is avoided, and a high recovery of the analyte can be achieved. The instrument is also easily switched between normal-phase and reversed-phase modes of operation simply by changing the mobile and stationary phases. With liquid chromatography, operation is limited by the composition of the columns and media commercially available for the instrument. Nearly any pair of immiscible solutions can be used in liquid-liquid chromatography provided that the stationary phase can be successfully retained. Solvent costs are also generally lower than for high-performance liquid chromatography (HPLC), and the cost of purchasing and disposing of solid adsorbents is eliminated. Another advantage is that experiments conducted in the laboratory can 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. The CCC separation process can be thought of as occurring in three stages: mixing, settling, and separation of the two phases (although they often occur continuously). Vigorous mixing of the phases is critical in order to maximise the interfacial area between them, and the analyte can distribute between the phases according to its partition coefficient. The mobile phase mixes with, then settles from the stationary phase throughout the column. The degree of stationary phase retention (inversely proportional to the amount of stationary phase loss or "bleed" in the course of a separation) is a crucial parameter. Common factors that influence stationary phase retention are flow rate, solvent composition of the biphasic solvent system, and the G-force created by rotation. The settling time is a property of the solvent system and the sample matrix, both of which greatly influence stationary phase retention. To most process chemists, counter current chromatography implies two biphasic liquids moving in opposing directions, as typically occurs in large process extraction units. With the exception of Dual-Flow (see below), most CCC & CPC applications have a stationary phase and a mobile phase. Even in this situation, counter current flows occur within the coil/rotor counter. Several researchers have proposed renaming both CCC & CPC to liquid-liquid chromatography, but others feel the name chromatography itself is a misnomer. CPC, or centrifugal partition chromatography, is arguably a more appropriate name, but CPC has historically applied only to sun centrifuges, and not planetary centrifuges, which are still called counter current chromatographs. This confusion was possibly added to, rather than resolved, when the CCC/CPC community chose to classify planetary CCC as HYDRODYNAMIC CCC and sun centrifuges (CPC) as HYDROSTATIC CCC. Typically most modern commercial CCC and CPC can inject 5 to 40 g per liter capacity. The range is so large, even for a specific instrument, let alone all instrument options, as the type of target, matrix and available biphasic solvent vary so much. Approximately 10 g per liter would be a more typical value, that the majority of applications could use as a base value. Unlike Flash Chromatography and HPLC, CCC & CPC can inject large volumes relative to coil/rotor/column volume. Typically 5 to 10% of coil volume can be injected. In some cases this can be increased to as high as 15 to 20% of the coil etc., volume. In comparison to flash chromatography/preparative/process HPLC, flows and total solvent usage can in most CCC/CPC be reduced by half and even up to a tenth of the needs of Flash Chromatography/Preparative/Process HPLC. An example of a major application of CCC/CPC is to take an extremely complex matrix, run on a generic biphasic with elution (possibly step gradient) and then extrusion, and fractionate original complex matrix into discrete narrow polarity bands, which could then be assayed for chemical composition or bioactivity. Working this scenario in conjunction with other chromatographic and non chromatographic techniques has the potential for rapid advances in compositional recognition of extremely complex matrices. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Countercurrent chromatography」の詳細全文を読む スポンサード リンク
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