In chromatography, there is a division of a substance between two phases. These are called the stationary phase (a solid liquid or liquid attached to a support material) and mobile phase (the gas or liquid that moves along the stationary phase). The partition coefficient is the distribution of a substance between these two phases.
Chromatography comes in two forms: liquid chromatography and gas chromatography.
Liquid chromatography uses liquid as the mobile phase, also called eluent.
In gas chromatography, carrier gas is used as the mobile phase. With a gas chromatograph, chromatography is only used with gas.
The three columns below show the separation principle. The system consists of a column filled with a solid stationary phase (brown) through which a liquid mobile phase flows (orange). When a mixture of two substances (yellow and red) is applied to the column, both substances are transported through the column, but because the yellow substance adheres more strongly to the stationary phase than the red substance, the two substances leave the column one by one. The mixture is thus separated.
There may be various reasons for wanting to separate a mixture and the requirements imposed on the chromatography system depend on the intended purpose.
With the use of chromatography equipment in laboratories, substances are separated from each other. This equipment can be divided into the following 6 groups: