Centrifuging

Centrifuging is a laboratory technique that uses a centrifuge to separate mixture components by density. When spun at high speed, denser particles are forced outward and sediment faster than lighter ones. The method can separate liquids from solids, cells from debris, or macromolecules like proteins and nucleic acids, depending on size, shape, and density. Key concepts include relative centrifugal force (RCF) and sedimentation rate.

Equipment ranges from bench-top to ultracentrifuges. Rotors are fixed-angle or swing-bucket. Operational parameters include speed (RPM or RCF), time, and temperature control. Proper tube balance and rotor integrity are essential for safety. The RCF relates to RPM and rotor radius by RCF = 1.118×10^-5 × r × (RPM)^2, with r in centimeters.

Applications cover preparative and analytic separations. In biology, centrifugation isolates organelles, membranes, and macromolecules; clarifies suspensions; and enables density-gradient separations. Clinically it separates blood components and concentrates cells for tests or transfusion. Industrial uses include dairy cream separation, liquid clarification, vaccine purification, and wastewater treatment.

Limitations include shear damage to delicate samples and incomplete recovery. Rotor failure or imbalance poses safety risks, making maintenance and safety practices essential. The technique dates to the early 20th century, with Theodor Svedberg pioneering ultracentrifugation and earning the Nobel Prize in Chemistry in 1926 for such work.