Column Chromatography is best described as which?

• A. A filtering process by which some molecules in a sample move out of a solution as it passes by a membrane
• B. Substances that separate into the top of a column packed with an adsorbent (as silica gel or alumina), pass through the column at different rates and collected
• C. A method to observe pigments in a material
• D. A method to measure pH

Answer: (B)

Column chromatography separates a mixture based on how strongly each component interacts with a solid stationary phase and a moving solvent. The column is packed with an adsorbent, like silica gel or alumina, and the sample is carried through by the solvent. Components that interact weakly with the stationary phase travel faster and exit the column earlier, while those that interact more strongly are retained longer and elute later. By collecting the eluate in fractions, you obtain the separated substances. This description best captures how column chromatography works, unlike filtration through a membrane, pigment observation, or pH measurement, which involve different techniques.