CHROMATOGRAPHY final preparing - CHROMATOGRAPHY...

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CHROMATOGRAPHY INTRODUCTION OF CHROMATOGRAPHY Definition : Chromatography is a physical method of separation that distributes components to separate between two phases, one stationary (stationary phase), the other (the mobile phase) moving in a definite direction. The eluate is the mobile phase leaving the column. The eluent is the solvent that carries the analyte. History of Chromatography : The history of chromatography spans from the mid-19th century to the 21st. chromatography , literally "color writing", was used—and named— in the first decade of the 20th century, primarily for the separation of plant pigments such as chlorophyll which is green) and carotenoids (which are orange and yellow). New forms of chromatography developed in the 1930s and 1940s made the technique useful for a wide range of separation process and chemical analysis t asks, especially in biochemistry. Working Pattern : Think of chromatography as a race. Waiting on the starting line, you've got a mixture of chemicals in some unidentified liquid or gas, just like. Chemicals in something like a moving liquid mixture spread out because they travel at different speeds over a stationary solid. The key thing to remember is that chromatography is a surface effect. As the liquid starts to move past the solid, some of its molecules (energetic things that are constantly moving about) are sucked toward the surface of the solid and stick there temporarily before being pulled back again into the liquid they came from. This exchange of molecules between the surface of the solid and the liquid is a kind of adhesive or gluing effect called adsorption . Now remember that liquid is actually a mixture of quite a few different liquids. Each one undergoes adsorption in a slightly different way and spends more or less time in either the solid or the liquid phase. One of the liquids might spend much longer in the solid phase than in the liquid, so it would travel more slowly over the solid; another one might spend less time in the solid and more in the liquid, so it would go a bit faster. Another way of looking at it is to think of the liquid as a mixture of glue-like liquids, some of which stick more to the solid (and travel more slowly) than others.
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This is what causes the different liquids within our original liquid mixture to spread out on the solid. For chromatography to work effectively, we obviously need the components of the mobile phase to separate out as much as possible as they move past the stationary phase. That's why the stationary phase is often something with a large surface area , such as a sheet of filter paper, a solid made of finely divided particles, a liquid deposited on the surface of a solid, or some other highly adsorbent material. Uses of Chromatography : Chromatography has evolved to be one of the most widely used chemical techniques to separate particles and contaminates in chemical plants. For example, in the chemical industries, pesticides and
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