Column Chromatography

Insert a cotton plug at the bottom of the column using a wire, add a layer of sand, and clamp the column in place. Fill the column about one-third with solvent (eluent), then create a slurry by mixing dry silica gel powder with solvent in a beaker.

Carefully transfer the silica slurry into the column using a spatula, adding more solvent as needed. Gently tap the column sides and use a pipette to rinse until all silica settles, then allow solvent to drip into a flask until the level sits just above the silica.

Dissolve the isolated mixture in the minimum amount of solvent possible and carefully pipette it onto the sand layer without touching the column sides. Drain a small amount of solvent so the sample enters the stationary phase as a concentrated, even band just below the sand.

Carefully pipette solvent down the column sides until the level is several inches above the sand, then pour additional solvent from a beaker while maintaining proper solvent level. Allow the column to drip at an optimal flow rate of a few drops per second, keeping the solvent level well above the sand at all times.

Collect the eluent in a series of small flasks (fractions) as the column runs. Use smaller fraction volumes (10 mL or less) when collecting material, watching for visible color bands to indicate where components are eluting, and continue until confident all relevant material has been collected.

Spot each collected fraction onto separate marked TLC plates with numbered reference lines. Develop the plates and identify which fractions contain only the desired product by comparing spots to known starting materials and predicted side products.

Pool all fractions that show only the target product on TLC with no other impurities. Transfer the combined fractions to a rotavap flask and evaporate the solvent to obtain the purified, isolated product.