Centrifuges

A laboratory centrifuge is an instrument that spins samples at high speed to generate centrifugal force, enabling the separation of components such as solids, liquids, and gases based on their densities.

It holds sample tubes in a rotor that spins at a set RPM. Centrifugal force pushes denser particles outward, forming a pellet at the bottom, while lighter components remain in the supernatant.

Benchtop centrifuges handle general lab separations at 4,000–15,000 RPM. Microcentrifuges spin small volumes (0.2–2 mL) up to 25,000 RPM. High-speed centrifuges reach 20,000–50,000 RPM for subcellular fractions. Ultracentrifuges achieve 50,000–100,000 RPM for macromolecules and viruses. Refrigerated centrifuges maintain 0–40 °C for temperature-sensitive samples. Floor-model centrifuges support large-volume or industrial applications.

You match your workflow needs: sample volume dictates micro vs. benchtop vs. floor model; required separation force determines speed (RCF/G-force); temperature control decides on refrigerated vs. non-refrigerated; rotor type (fixed-angle vs. swing-bucket) must suit your tubes; and your specific application (clinical, research, industrial) guides the final selection.

RPM (rotations per minute) is the speed at which the rotor turns. RCF (relative centrifugal force) is the actual force experienced by samples, expressed in × g, and calculated as: RCF = 1.118 × 10⁻⁵ × r(cm) × (RPM)², where r is the rotor radius in centimeters.

Always balance tubes symmetrically, inspect rotors and tubes for cracks before use, close the lid securely, wear proper PPE (lab coat, goggles, gloves), and never open the lid until the rotor has fully stopped.

Unplug and remove rotors before cleaning. Wipe the chamber and rotors with mild detergent and water. Inspect seals and O-rings regularly. Lubricate the rotor spindle according to the manufacturer’s instructions. Schedule periodic calibration and professional servicing.

A refrigerated centrifuge maintains controlled temperatures (typically 0–40 °C) during separation, preserving the integrity of heat-sensitive materials like enzymes, proteins, and live cells.

Microcentrifuges reach ~20,000–25,000 RPM (up to 100,000 × g). Benchtop units go ~4,000–15,000 RPM (up to 20,000 × g). High-speed models achieve ~20,000–50,000 RPM. Ultracentrifuges operate at ~50,000–100,000 RPM (up to 1,000,000 × g).

They’re used for blood plasma or serum separation, DNA/RNA extraction, protein purification and fractionation, organelle isolation, virus and nanoparticle pelleting, and sample clarification.