Instrumentation prefractionation

In on-line multidimensional HPLC (MDHPLC) two relatively high-efficiency columns are coupled in an instrument, via the use of valves, traps and other means. In LC-LC the precolumn is used for sample cleanup and prefractionation, before introduction of the fraction of interest to the analytical column. Much of the instrumentation for MDHPLC is the same as that in conventional one-dimensional experiments. However, the additional complexity of MDHPLC experiments leads to greater difficulties than those found in conventional HPLC ... 

Automated purification systems should have the capacity to take a crude sample or prefractionated extract through to a series of pure compounds with limited human input. A number of companies produce automated purification systems. Automated purification of a target compound can be configured quite readily on many instruments using, for example, a UV, MS, or evaporative light scattering (ELS) signal. 

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