Column Chromatography

Review the TLC of your mixture to identify the target compound and contaminants. Select an appropriate solvent system (3:1 hexane to ethyl acetate in this case) that separates your compound of interest with an Rf around 0.3 from other contaminants.

Clamp the column to a ring stand and add a funnel to the top. In the fume hood, pour silica gel to the recommended height (5 inches). Transfer the funnel and silica gel to a large Erlenmeyer flask and create a slurry by adding solvent while stirring until pourable.

Place an Erlenmeyer flask under the column with the stopcock open. Pour the slurry through a wide-mouth funnel and immediately rinse the sides with solvent using a pipette. Jostle the column with your hands to remove air bubbles trapped in the silica gel bed.

Scoop sand (approximately 0.5 cm) onto the top of the silica gel bed and rinse it down with solvent to create an even buffer layer. Use air pressure to push liquid down to the sand level (but not into it), then release air and close the stopcock.

Prepare test tubes in a rack underneath the column. Dissolve your solid sample in an appropriate solvent and use a long-stemmed pipette to carefully drip the sample drop-by-drop onto the sand layer. Rinse the sample vial with additional solvent and add the rinse to the column as well.

Open the stopcock to drain the sample liquid until it just reaches the top of the silica gel. Rinse the column sides with solvent twice, allowing it to drain to the sand layer each time. Add fresh solvent to the column until the level fills into the bulb area.

Open the stopcock to elute the column and collect the eluate in test tubes, moving to a fresh tube as each fills. Apply air pressure to the column to speed elution and separation. Continue collecting fractions while monitoring the solvent level—refill if it drops below the sand layer—until all colored compounds have eluted off.

Use TLC analysis to identify which fractions contain your target compound. Combine all fractions with the desired product into a single flask for further processing or evaporation.