A clinical centrifuge is a laboratory instrument used in medical and research settings. It processes patient samples, preparing them for various analyses. It separates different components within liquid mixtures. It supports diagnostic tests and research, making it indispensable in modern laboratory workflows.
Separating Components by Density
A clinical centrifuge separates fluid mixtures into their parts based on density. Centrifugation applies centrifugal force to samples. It spins samples at high speeds, typically 1,000 to 3,000 revolutions per minute (RPM).
As it spins, denser components settle at the bottom of the tube. This forms a pellet. The less dense liquid remains at the top, forming the supernatant. This layering allows isolation and analysis of specific components.
Key Applications in Specimen Processing
Clinical centrifuges process blood samples for diagnostic purposes. When centrifuged, whole blood separates into layers. Red blood cells, the densest, form a pellet at the bottom. Above this, a thin, whitish “buffy coat” contains white blood cells and platelets.
The clear, yellowish liquid layer at the top is either plasma or serum, depending on how the blood was collected. To obtain plasma, blood is collected in tubes containing an anticoagulant, which prevents clotting; the centrifuge then separates the cellular components from this liquid. For serum, blood is allowed to clot at room temperature for about 15-60 minutes before centrifugation, which removes the clot and leaves the serum supernatant. Both plasma and serum are then used for chemistry, immunology, and other specialized tests, providing information about a patient’s health.
Centrifugation is also routinely applied in urinalysis to prepare urine samples for microscopic examination. A measured volume of urine, often 5 milliliters, is transferred to a conical centrifuge tube. This sample is then spun, typically for about 5 minutes at a relative centrifugal force (RCF) of approximately 450g, which can correspond to 1500-2000 RPM depending on the centrifuge model.
This process concentrates any solid elements, such as cells, casts, or crystals, into a pellet at the bottom of the tube. The majority of the liquid supernatant is then carefully removed, leaving a small volume (around 0.5 mL) to resuspend the sediment. This concentrated sediment is then placed on a microscope slide to identify abnormalities, assisting in the diagnosis of kidney diseases or urinary tract infections.