In the context of TLC and column chromatography, which statement correctly compares the two methods?

The comparison that indicates that solvent flows through the adsorbent in column chromatography is accurate and exemplifies the fundamental operational differences between the two techniques.

In column chromatography, a vertical column is packed with a stationary phase (adsorbent), such as silica gel or alumina. The mobile phase (solvent) is introduced at the top and flows downward through the column under the force of gravity. As the solvent moves, it carries the sample components through the adsorbent material, allowing for separation based on differences in their affinities for the stationary phase and their solubility in the solvent.

This contrasts with thin-layer chromatography (TLC), where the stationary phase is spread in a thin layer on a plate, and the solvent moves up the plate via capillary action rather than gravity. In TLC, the solvent front can reach a maximum level but typically does not stop at a specific edge unless manually drawn back.

Understanding the flow dynamics in both methods is crucial, as they underpin the principles of separation and analysis in chromatography. This knowledge is fundamental for predicting how different substances will behave in these settings based on their chemical properties.