Which of the following methods can be used to seperate blood cells from plasma?

Step 1: Analyze the question Blood is a suspension. Blood cells (red cells, white cells, platelets) are small solid particles dispersed in plasma, which is a liquid. We need a method that separates these solid cells from the liquid.

Step 2: Explain the concept Centrifugation spins a mixture at high speed. The denser particles are pushed to the bottom of the tube, and the lighter liquid stays on top. It is used for suspensions whose particles are too fine to settle quickly under gravity or are too small to be caught cleanly by filter paper.

Step 3: Evaluate each option

• A. Centrifugation: Correct. Spinning blood makes the denser cells settle at the bottom, and the plasma stays on top. This is exactly how laboratories and hospitals separate blood cells from plasma.
• B. Filtration: Not suitable. Blood cells are very small and soft. They would clog or pass through ordinary filter paper, and the separation would be poor.
• C. Chromatography: Used to separate dissolved substances, such as dyes or pigments, based on how fast they move through a medium. It is not used to separate cells from a liquid.
• D. Distillation: Separates liquids with different boiling points. Heating would destroy the cells and the proteins in the plasma, so it is not appropriate.

Step 4: Answer The correct option is A. Centrifugation.

Exam tip: Match the method to the mixture:

• Suspension of fine particles in a liquid (blood, cream from milk): centrifugation
• Insoluble solid in a liquid with large particles (sand in water): filtration
• Dissolved coloured substances: chromatography
• Miscible liquids with different boiling points: distillation

If you see "blood" and "separate" together, think centrifuge.