Note for CHEM 625 at KU (2)
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This 2 page Class Notes was uploaded by an elite notetaker on Friday February 6, 2015. The Class Notes belongs to a course at Kansas taught by a professor in Fall. Since its upload, it has received 16 views.
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Date Created: 02/06/15
Column Chromatography Column chromatography is an analytical technique that is used to separate and isolate the componenm of a reaction mixture CC and TLC are considerably similar both use an adsorbent such as cellulose starch alumina or silica for the stationary phase and organic solvents as the mobile phase In a TLC experiment compounds are separated as they move up the plate with the mobile phase while in a column chromatography experimenm the compounds are separated as they travel down a column with the mobile phase CC uses a polar stationary phase and compounds are separated off the column from lnon polar to polari molecule while in Reversedphase column from polar to nonpolar molecule Comment TPl This is important Packing the column There are 2 basic methods of packing chromatography columns dry packing the slurry method In either packing method the solvent level needs to be kept just above the top of the adsorbent to prevent the column from running A dry column would result in the formation of bubbles and channels within the column which means no partitioning between the mobile and stationary phases leading to poor separation Do not ever let a colurnn run dry Loading the Sample onto the Column Load concentrated samples on the column at the same time in order to get an effective separation To lead the sample this concentrated solution is added very carefully to the top of the column so that the top of the silica is not disturbed Running and Monitorng the Column Starting with a nonpolar solvent lto help carry nonpolar compounds down the column faster Comment TPZ Important while the more polar compounds move slowly down the column then increase polarity as needed This increases the chances of successfully separating your compounds The best eluent system to use to separate a reaction mixture is a moderately polar solvent because it gem the job done quickly and has enough separation in the dos in the TLC layer Primary Factors that in uence separation are Nature of the stationary phase normal or reverse Amount of absorbentsorbent silicaalumina stationary Mobile phase composition eluent polarity Sand is added to top of the column to make it easier to add more solvent to the column without disturbing the top of the column
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