ABSTRACT
The origins of countercurrent chromatography (CCC) go back to 1950 when the Craig countercurrent instrument was developed [1,2]. The early instruments were cumbersome and delicate; their operation required close attention and the experiments lasted for several days. The technique was widely used for separation and purification of natural products, particularly alkaloids, which are ideally suited for separation using chloroform, methanol, and dilute acid systems, one of the few solvent systems that could be used on the Craig instrument. Despite the shortcomings in instrumentation, CCC remained an important tool for the natural products chemist. This continued interest led to the development of droplet countercurrent (DCC) and rotational locular countercurrent (RLCC) instruments and then the high-speed countercurrent chromatography instruments (HSCCC) of today, which are much more efficient and user-friendly than their predecessors. Even though DCCC and RLCCC instruments are still available, often used for sample enrichment [3], they are being replaced by HSCCC instruments. CCC has been used extensively as an efficient chromatographic method in natural product isolations. However, utilization of the potential of CCC in other areas of chemistry has been limited. There are a few reasons for this slow acceptance of CCC:
Besides being a preparative method, CCC has been perceived as a complicated technique that requires an understanding of hydrodynamics, ability to interpret phase diagrams, and a good knowledge of partition coefficients in order to perform a simple separation. The difficulties involved in automating HSCCC instruments also contributed to their limited use. The advancements in the instrumentation and the greater understanding of the technique would make CCC a useful tool with a variety of applications.
