Which statement best defines chromatography?

• A. A technique used to measure enzyme activity.
• B. A method to determine the sequence of DNA.
• C. A technique used to separate the components of a mixture based on their tendency to travel across a surface.
• D. A method to separate isotopes by mass.

Answer: (C)

Chromatography hinges on separating mixture components by how they move with a moving phase as they interact with a stationary surface. Different substances have different affinities for the stationary phase and solubilities in the mobile phase, so they travel at different speeds and end up separated as distinct spots or bands. That idea—components being separated because they differ in their tendency to travel across or along a surface with the flowing solvent—is exactly what the technique describes.

Other options describe different lab tasks: measuring enzyme activity, sequencing DNA, or separating isotopes by mass, which are not what chromatography is primarily about.