OCHEM Column and TLC Chrom 5

OCHEM Column and TLC Chrom 5 - Column and Thin Layer...

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Column and Thin Layer Chromatography of Spinach Extracts Lindy Hilpert Brad Hutnick Organic Chemistry 330 October 10, 2007
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Introduction The purpose of this lab is to separate spinach extract into some of its components using column chromatography. It is also to perform some analytical calculations on the separated molecule using thin layer chromatography. Reactions, Theories, and Mechanisms Chromatography is a way of separating molecules by way of partitioning based adsorption between mobile (solvent) and stationary (adsorbent) phases. The molecules separate based on the polarity interactions of the sample, adsorbent, and solvent molecules. This process is based on the fact that polar molecules dissolve polar molecules and non polar molecules dissolve non polar molecules. Polarity is a measure of how the electrons in a bond are shared. In a polar bond, the electrons are more attracted to one of the atoms than the other. In a non polar bond, the electrons are shared equally between the two atoms. There were two types of chromatography used in the experiment: column and thin layer. A column is a long glass tube with an opening at one end that closes with a stopcock and the other end completely open (Refer to Figure 1). In column chromatography, the adsorbent acts as the stationary phase. It fills most of the column. The solvent, or eluent, is the mobile phase. An eluent is a substance used as a solvent in separating materials in elution. It is passed through the column and stationary adsorbent. The column is filled by using the dry packing procedure. The column is loaded with the solution of molecules to be separated. The eluent is then passed through the column and carries the molecules with it. The molecules are carried with the eluent depending on their polarity. If the eluent is non polar, then it will carry the non polar molecules through the column with it. If the eluent is polar, then it will carry the polar molecules through the column with it. The molecules that are carried through the column can be collected in a beaker and saved for further analysis. Column chromatography can be used for purification of a substance and separation of molecules. An important fact about column chromatography is that it can only be done using a non polar solvent first. If a polar solvent is added first, it will carry all the polar and non polar molecules through the column with it. Only a non polar solvent will leave the polar molecules behind. Thin layer chromatography uses a chromatography plate (Refer to Figure 2 and the sample chromatography plate). A chromatography plate is a small rectangle that has a thin layer of adsorbent (alumina) on top of an inert carrier sheet. The plate acts as the stationary phase and the eluent acts as the mobile phase. The stationary phase is alumina. The alumina is finely ground before it is put on the plate to produce analytical units.
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OCHEM Column and TLC Chrom 5 - Column and Thin Layer...

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