Chromatography is analytical chemistry method which is used (and useful) for the separation of complex mixtures of chemical compounds. The main mechanism of the separation is repeatable distribution of the tested compound in between two different phases.
Usually, one phase is solid, fixed in the separation device and the other is moving and flows through the unit. If gas is a second phase, we are referring to the gas chromatography, in case of liquid as a second phase the name is liquid chromatography.
The device where separation takes place is called chromatographic column. This cylindrical shape column is filled with the different kinds of materials – stationary phases. These materials are usually spherical silica particles with different, but well defined, surface chemistry.
The mobile phase flows through the column together with sample (mixture of compounds). Each compound has various affinity to the surface of stationary phase and therefore is separated form each other. In case of ideal state all compounds are eluted from the column in separated bands.
Various techniques are used to recognize these bands and transform them into the signal. In most of the cases the signal draws chromatographic peak – the “hill like” curve describing Gauss distribution.