"Chromatography" is an umbrella term covering physical methods in which substances are separated via distribution between a stationary and mobile phase. HPLC (High-Performance Liquid Chromatography) is a separating process in which a liquid sample is transported through a stationary phase under high pressure. Depending on the nature of the interaction between the phases and the sample, we distinguish between adsorption chromatography, partition chromatography, ion-exchange chromatography, sizeexclusion chromatography and affinity chromatography. The processes of adsorption chromatography and partition chromatography are the chief processes used in HPLC. HPLC uses partition particles with grain sizes of a few µm; it thus achieves high numbers of plates or trays, but at the same time, requires a high counter-pressure to be overcome during transport of the mobile phase through the thin separation column (of a few millimeters diameter). All parts must be interconnected without any dead volume wherever possible and must be pressure-stable (up to 300 bar).
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