Planar chromatography is a form of liquid chromatography: A liquid mobile phase dissolves the substances of a mixture and transports them through a flat (planar) stationary phase. Different affinities of substances to the two phases afford separation as they cause different retardation with respect to the velocity of the mobile phase. In column chromatography, this affects the time of elution (retention time) while in planar chromatography the position of substance relative to the front of the mobile phase on the plate is changed. Because planar chromatography takes place in a developing chamber, also a gas phase is established, which can influence the separation.
There are two forms of planar chromatography: Paper Chromatography and Thin-Layer Chromatography (TLC). Planar chromatography is performed in off-line mode, which means that the principle steps of the process (sample application, development, derivatization, detection, evaluation) are independent in time and location. This leads to some specific advantages:
- great flexibility in the choice of stationary and mobile phases
- parallel analysis and visual comparison of multiple samples and standards
- single-use of the stationary phase reduces the need for sample clean-up
- possibility of multiple detections without the need to repeat chromatography
- convenient chemical derivatization of separated substances and detection of biological activity
- low cost
- rapid
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