Which separation technique is based on differential interactions with a stationary phase and is commonly used to separate components dissolved in a liquid or gas?

• A. Filtration
• B. Distillation
• C. Chromatography
• D. Crystallization

Answer: (C)

Differential interactions with a stationary phase drive separation in chromatography. In this approach, a mobile phase carries the mixture past a material that acts as the stationary phase; each component interacts with that surface to a different extent. Those with stronger interactions spend more time attached and move more slowly, while those with weaker interactions travel faster, causing the components to separate as they move along. This is ideal for mixtures dissolved in a liquid or gas because you can choose the stationary and mobile phases to exploit differences in polarity, hydrogen bonding, or other interaction types. For example, polar compounds may stick longer to a polar stationary phase, separating from nonpolar ones. By comparison, filtration relies on particle size, distillation on boiling point differences, and crystallization on solubility and crystal formation, so they don’t separate by differential interactions with a stationary phase in the same way.