7.9: Macroscale Column Chromatography

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Table 7.9: Procedural summary for macroscale column chromatography.

Make sure there is a frit or cotton plug in the bottom of the column. Fill the column with silica or alumina to 5-6 inches in the fume hood.	Pour the adsorbent into an Erlenmeyer flask and add eluent to make a pourable slurry. The eluent should give the desired component an \(R_f\) of 0.35 by TLC.	Pour the slurry and immediately rinse the sides of the column with eluent and a pipette. Jostle the column to remove air bubbles. Use air pressure to pack the column. Keep it perfectly vertical.	Add \(0.5 \: \text{cm}\) of sand. Rinse the sand off the sides carefully with a swirling motion. Don't disrupt the top surface of the silica or alumina with rinsing.

Adjust the eluent level to the sand layer, and then add the sample (pure liquid, dissolved in \(\ce{CH_2Cl_2}\), or solid adsorbed onto a portion of silica). Rinse the sides and use air pressure to force the eluent down onto the silica/alumina layer.	Fill the reservoir with eluent (carefully to not disrupt the top surface). Use steady air pressure to elute the column. Collect fractions in test tubes in a rack (keep in order).	Rinse the column tip if a component has finished coming off the column. Possibly increase the eluent polarity to make components elute faster. Never allow the eluent to drop below the top of the adsorbent column.	Use TLC to determine the purity of the fractions, and combine appropriate fractions. Remove the solvent with the rotary evaporator.