Zentrifugation

Zentrifugation, or centrifugation, is a laboratory technique that uses centrifugal force to separate components of a mixture based on differences in density, size, and shape. By spinning samples at high speed, denser or larger particles sediment more rapidly than lighter components.

The method relies on a rotor inside a centrifuge; acceleration is expressed as relative centrifugal force (RCF) in g. RCF can be estimated from rpm and rotor radius with RCF ≈ 1.118 × 10^-5 × r(cm) × (rpm)^2.

Types include differential centrifugation (stepwise sedimentation of components), density gradient centrifugation (separating by buoyant density), and isopycnic/equilibrium centrifugation (particles band at their buoyant density).

Equipment comprises benchtop and high-speed centrifuges, rotors (fixed-angle or swinging), and tubes. Procedures require balanced loading, temperature control, and careful selection of speeds, times, and media to minimize damage to samples.

Applications span biology and medicine: isolation of organelles, viruses, and macromolecules; purification of proteins and nucleic acids; and clinical tasks such as plasma separation and sedimentation rate testing.

History: Theodor Svedberg pioneered analytical ultracentrifugation in the early 20th century, enabling precise measurement of sedimentation rates. His work contributed to the understanding of dispersed systems and earned him the Nobel Prize in Chemistry in 1926.

Safety and limitations: rotor imbalance, heat generation, and shear forces can affect samples. Proper calibration, maintenance, and adherence to protocols are essential to ensure accurate results and to prevent equipment damage.