Chromatography is a scientific technique that permits the separation of a substance's constituent chemicals by taking advantage of chemicals' diffusion properties. The process is named after chroma, which is the Greek word for color, and the technique was first demonstrated by separating plant pigments into colored bands, according to HowStuffWorks.
Chromatography was first developed in 1906 by the Russian botanist Mikhail Tswett. The technique is available in two forms, gas and liquid, which are used with different types of materials chemists work with.
Gas chromatography is intended for use with solutions with chemical components that do not vaporize at high temperatures, according to ChemPages. It is also appropriate for analyzing samples that are only available in very small quantities, such as those typically measured in micrograms.
Liquid chromatography differs from gas chromatography in that the substance being analyzed is held in a liquid suspension throughout the process. In this method, the target substance is dissolved in a solvent and fed through high-pressure tubing at a rate of a few milliliters per minute until the sample separates. It then passes in front of a sensitive detector that can discriminate variations in hue too subtle for human eyes to perceive, as described by Waters.