What is the primary purpose of a centrifuge in laboratory testing?

• A. To sterilize equipment.
• B. To measure pH.
• C. To separate components of blood or other specimens by density.
• D. To amplify DNA.

Answer: (C)

Centrifugation uses centrifugal force to separate components of a mixture according to density. When a sample like blood is spun rapidly, heavier components move toward the bottom while lighter components stay toward the top, creating distinct layers. In blood, that typically means a bottom layer of red blood cells, a middle layer of white cells and platelets, and a top plasma or serum layer. This separation is crucial because it lets clinicians access or analyze the specific component needed, such as using plasma for chemistry tests or isolating cells for microscopic examination or further processing. The other options describe different lab processes: sterilization relies on heat or chemicals, not separation by density; pH measurement uses a sensor or indicator, not separation; DNA amplification requires enzymatic replication techniques, not just spinning to separate components. So the centrifuge’s main purpose is to separate components by density.