Which technique separates mixtures based on the differential movement of components on a surface?

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

Answer: (A)

Chromatography works by letting a mixture move with a moving phase across a surface coated with a stationary phase. Each component interacts differently with that surface and with the solvent, so they travel at different speeds as the solvent moves. This difference in movement causes the components to separate into distinct spots or bands on the surface. Techniques like thin-layer chromatography or paper chromatography illustrate this clear separation as components migrate at different rates.

Distillation relies on boiling points to separate components, filtration uses particle size or phase boundaries, and gel electrophoresis separates mainly by charge and size in a gel under an electric field—none rely on differential movement on a surface in the same way chromatography does.