centrifuged

Centrifuged refers to a material that has undergone centrifugation, a process in which a mixture is subjected to high-speed rotation in a centrifuge to separate components by density, size, or shape. The term derives from centrifuge, the device that generates the force through spinning. In laboratory practice, samples are often described as centrifuged at a given speed and duration.

Principle: When spun, centrifugal force pushes denser components outward, forming distinct layers or sediments within a tube. Separation efficiency depends on the relative centrifugal force (RCF), rotor design, viscosity, and density differences among components. RCF can be estimated from speed and rotor radius, commonly approximated by RCF = 1.118×10^-5 × r × rpm^2, where r is the radius in centimeters.

Equipment and parameters: Centrifuges range from compact microcentrifuges to ultracentrifuges capable of generating very high g-forces. Key settings include speed (rpm or RCF), duration, and temperature control. Rotor types include fixed-angle and swinging-bucket variants. Proper balancing and adherence to manufacturer specifications are essential to protect the equipment and ensure consistent results.

Applications: Centrifugation clarifies liquids, separates plasma or serum from blood cells, and isolates cellular components such as nuclei, mitochondria, or ribosomes. It enables density gradient centrifugation for purification of macromolecules and particles, including viruses and organelles, as well as purification of nucleic acids and proteins. Ultracentrifugation achieves extremely high g-forces for very small objects.

Limitations and safety: Centrifugation can generate heat and shear forces that may damage sensitive samples. Improper balancing, rotor wear, or exceeding recommended speeds pose safety risks. Not all mixtures separate cleanly, and some components may remain mixed or degrade under centrifugal forces.