What is Chromatography?
{{nosources|date=November 2021}} '''Chromatography''' is a method for [[separation process|separating]] the parts of a mixture for [[chemical purification|chemical analysis and identification]]. It works by using differences in the speed at which the mixed substances move through special ''media'', or chemical substances. It uses a ''stationary phase'' (a [[solid]]) and a ''mobile phase'' (a liquid or a gas). The fluid mobile phase flows through the stationary phase. Chromatography is much used in [[biochemistry]] and [[analytical chemistry]]. == Flat-plane chromatography == The stationary phase is a flat plane, such as paper, or a substance on glass. === Paper chromatography === {{main|Paper chromatography}} [[File: Chromatography_tank.png|thumb|right|230px| Chromatography jar]] ''Paper chromatography'' is an old technique for separating and identifying mixtures that are (or can be) coloured. It has been largely replaced by ''thin layer chromatography'', but is still a powerful teaching tool. ''Double-way paper chromatography'', also called 'two-dimensional chromatography', uses two [[solvent]]s and rotates the paper 90° in between. It is useful for separating complex mixtures of compounds having similar polarity, for example, [[amino acids]]. The compounds used initially ensures you to know whether the colour is pure, (one substance only) or mixtures (multiple substances.) === Thin layer chromatography === {{main|Thin layer chromatography}} Thin layer chromatography (TLC) is a common laboratory technique similar to paper chromatography. Instead of a stationary phase of paper, it uses a thin layer of [[adsorption|adsorbent]] like [[silica]] [[gel]], [[alumina]], or [[cellulose]] on a flat substrate. Compared to paper, it has the advantage of faster runs, better separations, and the choice between different adsorbents. For even better resolution and to allow for quantification, high-performance TLC can be used. == Column chromatography == ''Column chromatography'' separates [[Chemical compound|compo