Which of the following is NOT one of the three basic separation techniques?

• A. Centrifugation
• B. Filtration
• C. Dialysis
• D. Chromatography

Answer: (D)

The idea being tested is distinguishing simple, two-stage physical separations from a more specialized analytical method. Centrifugation, filtration, and dialysis are straightforward techniques that separate components based on basic physical properties: density and sedimentation (centrifugation), particle size relative to a filter (filtration), and size-based diffusion across a semipermeable membrane (dialysis). These methods don’t require a mobile phase or a distinct interaction with a second phase; they work with a single phase and a barrier or force to separate components.

Chromatography operates on a different principle. It uses a stationary phase and a mobile phase, and separation occurs because different components interact with these phases to varying degrees (adsorption, partitioning, or size-based exclusion, depending on the type). This approach is more complex and versatile, often used to separate and analyze substances that are not easily separated by simple size or diffusion methods.

Because chromatography relies on those phase interactions and often more elaborate setups, it’s not considered one of the basic trio of separation techniques.