Which technique is used to separate the components of a mixture based on their tendency to travel or be drawn across the surface of another material?

• A. Distillation
• B. Filtration
• C. Gel Electrophoresis
• D. Chromatography

Answer: (D)

Chromatography separates components by differential movement of each substance as it is carried by a moving phase over a stationary surface. Different components interact with the stationary phase to varying degrees, so some travel farther with the solvent front while others move more slowly or stay near the origin. This produces distinct separated components on the surface or within the medium, such as on a TLC plate or paper.

For example, in thin-layer or paper chromatography, a small sample is placed on a plate, a solvent moves through by capillary action, and each component migrates at a different rate depending on how strongly it interacts with the plate versus the solvent. The result is a separation based on those interactions.

Other techniques don’t rely on this surface-based differential travel: distillation separates mixtures by boiling points; filtration separates by particle size; gel electrophoresis uses an electric field to move charged molecules through a gel.