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Unformatted text preview: 7 Thin Layer Chromatography I: The Separation of Compounds by Thin Layer Chromatography 41 u Online edition for students of organic chemistry lab courses at the University of Colorado, Boulder, Dept of Chem and Biochem. (2009) Experiment 7 Thin Layer Chromatography I: The Separation of Compounds by Thin Layer Chromatography Techniques: Thin Layer Chromatography (read the section on TLC in the Handbook for Organic Chemistry Lab ). Thin layer chromatography (TLC) is another of the chromatographic methods used to separate mixtures of compounds. It is generally applied as a qualitative analytical tool rather than as a means of puri f cation, however, this technique can also be used to separate small quantities of compounds from mixtures. TLC is simple, inexpen- sive, and gives the user a quick answer as to how many components are in a mixture. Sometimes TLC can be used to identify the compounds in a mixture when compari- sons are made with known materials. The proper choice of a solvent is critical to separation of a given mixture by TLC. Generally, the more polar a solvent is, the more effective it is at eluting both polar and non-polar compounds. This is because a polar solvent more effectively com- petes with the compounds for adsorption on the relatively polar surface of the adsor- bent. The elutropic series, or the order of ability to displace solutes from adsorbents, is given for a number of solvents in the table to the right. (Tables of elutropic series are in the TLC section of the Chromatography chapter in the Handbook for Organic Chemistry Lab .) The best solvent for a particular application often must be determined by a trial and error process. Generally, a mixture of solvents, or solvent system, is used in TLC....
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