Chromatography separates the components of a mixture based on their affinity for a stationary or mobile phase. Each compound leaves the system at a different rate. The quicker a compound is flushed through, the lower its affinity for the stationary phase.
For a chromatographic analysis, two phases are used to determine the behavior of the compounds that form a mixture. As the stationary phase remains immobile, the mobile phase transports the sample that needs to be analyzed. A compound that has a high affinity for the stationary phase takes longer to leave the system, while a compound that has a high affinity for the mobile phase is flushed through very quickly. Sometimes, analytical instruments are paired with chromatography to provide accurate, highly detailed results.
There are several chromatographic methods that are used to identify and separate compounds, including gas chromatography, high-performance liquid chromatography, thin-layer chromatography and liquid chromatography. Gas chromatography is suitable for analyzing organic compounds and uses a gaseous mobile phase and a liquid or solid stationary phase. High-performance liquid chromatography is a highly efficient method, as it uses high-pressure pumps to improve the separation process. Metal ions and organic compounds are separated by liquid chromatography, a method that uses a solvent as a mobile phase.
Chromatography is used to analyze small samples of complex mixtures, such as drugs, pesticides or foods.