Centrifugare

Centrifugare, known in English as centrifugation, is a laboratory technique that uses spinning to apply centrifugal force to a sample, causing its components to separate according to density. The method is widely used in biology, chemistry, medicine, and industry to isolate cells, organelles, proteins, nucleic acids, and colloidal particles.

Principle: When the sample is rotated at high speed, denser material tends to move outward and toward the bottom of the vessel, while lighter material remains toward the top. The separation is governed by relative centrifugal force (RCF), which depends on rotor radius and angular velocity.

Equipment and operation: A centrifuge consists of a motor, a rotor, and containment for samples. Speeds are expressed as RCF or rpm. Rotors are either fixed-angle, which hold tubes at a fixed tilt, or swinging-bucket, which orient tubes vertically during spinning. Ultracentrifuges reach very high g-forces, allowing finer separations such as of subcellular components.

Methods: Differential centrifugation uses a series of increasing speeds to progressively pellet larger components, enabling isolation of organelles or bacteria. Density-gradient centrifugation uses a medium such as sucrose or cesium chloride to separate objects by density, often yielding purer fractions.

Applications: In medicine and research, centrifugation is used to prepare blood components, purify proteins, isolate mitochondria or ribosomes, and clarify suspensions in dairy and biotechnology.

Safety and quality: Proper balance of tubes, rotor integrity, and temperature control are essential. Imbalance can damage equipment or cause accidents; overheating can denature samples and skew results.