Chromatography is a very common lab technique that is used to separate different components of a complex mixture. It takes the advantage of differential solubility of different components of a mixture. This means that only those mixtures can be purified (or broken down into sub- components) by this technique whose components show differential solubility in another solvent.
Let us assume a mixture M is composed of two components A and B. In the most common types of chromatography, the Mixture M is dissolved in another liquid, which is called as the mobile phase. Mobile phase, along with the subject mixture, moves through a non-mobile phase called as the stationary phase. In order for this technique to work, the components A and B should have different affinities for the mobile and stationary phases.
When placed on a chromatogram (which could be a paper as in Paper chromatography or a column as in Gas chromatography), the component that shows higher affinity to the mobile phase, moves faster. The component, on the other hand, that shows lower affinity to mobile phase or higher affinity to the stationary phase, moves slowly.
Chromatography finds a wide practical use in the following many areas or industries. Some of them are listed below.
- Isolation, identification and analysis of different components of various mixtures.
- Testing urine for the presence of proteins, ketone sugars etc. for medical disorders and also the presence of banned drugs (like cocaine, Heroin, etc.) in criminal cases of drug addiction and overdose.
- Identification of some rare biological species.
- Testing of blood samples for forensic studies and medical sciences.
- DNA sequencing, RNA/DNA fingerprinting etc.
- Studying environmental pollution. For instance finding different components/pollutants present in a given water sample collected from a polluted water body.
- Detection of explosive matter on the airports and other high-alert areas.
- Detection of pesticides, DDT, dyes, illegal additives and adulterants in food and drinking samples.
- Separation and analysis of various amino acids like proline, glycine, etc. from proteins samples.
- Testing the antibiotics for purity and checking the concentration of their constituents, etc.