Question

In column chromatography, why is it important not to let the level of the eluding to drop below the top of the absorbent column?

Answer 1

In column chromatography, it is imperative that the adsorbent (the column packing material) is never run dry. Hence, the solvent is added on top of the adsorbent to make sure that the adsorbent is wet and the analytes can easily run down the column. Moreover, the solvent helps to remove void spaces in between the adsorbent molecules by bringing the adsorbent molecules close to each other. A dry column yields poor resolution and separation of the analytes and hence, the column must never be allowed to dry up.