Which device separates substances by density by spinning them at high speeds?

• A. Mass Spectrometer
• B. Spectrophotometer
• C. Centrifuge
• D. Chromatography

Answer: (C)

Separating substances by density using rapid spinning relies on centrifugal force. A centrifuge spins a sample at high speed, creating a strong outward force that pushes heavier, denser components toward the bottom of the tube while lighter components remain higher in the liquid. Over time this creates distinct layers that can be separated, which is especially useful for things like separating blood cells from plasma. The effect is driven by density differences, not chemical interactions or optical properties, and is quantified by the g-force (RCF) generated by the rotor.

This approach is different from other instruments. A mass spectrometer uses electric and magnetic fields to separate ions by mass-to-charge ratio, not by density in a physical spin. A spectrophotometer measures how much light a sample absorbs to infer concentration, without physically separating components. Chromatography separates substances based on how strongly they interact with a stationary phase versus a mobile phase, not primarily by density under rotation.