In general, chromatography is a system that will separate individual components located within a mixture from one another. The chemical mixture is dissolved in a carrier, either a gas or a liquid, called the mobile phase. This mixture then flows past a stationary phase which interacts with the mobile phase components. The more a particular component interacts, the more time it will take to travel. This enables the components to be separated into bands over time.

Chromatography Diagram

The slower green components are separated from the faster moving red components.

The two main types of chromatography used at the Environmental Services Program are gas chromatography and liquid chromatography. For gas chromatography (GC) the mixture is volatilized onto a stream of moving gas, whereas in liquid chromatography the mixture remains in liquid solvent solution. The liquid method of chromatography most often utilizes a stationary phase under high pressure. Hence the name HPLC is often used, which stands for high pressure liquid chromatography.