What Is an Ultracentrifuge?

An ultracentrifuge is a scientific tool or instrument that is capable of spinning objects or liquids very fast within a small, compressed chamber. Depending on the specific purpose these tools can be very small or quite large — many can fit easily on a tabletop, while others take up entire rooms. The ways in which they work and their basic goals are usually about the same no matter the specifics, though. In general, ultracentrifugation is carried out at speed faster than 20,000 rpm and is used to separate tiny particles from one another in order to determine their sizes and molecular weights. It is also widely used to study high polymers, particularly proteins, nucleic acids, viruses, and other biological macromolecules. There are preparative and analytical versions of this tool, and both are used in polymer science, biochemistry, and molecular biology. Though the machines are usually considered safe, the speeds at which they operate can present some risks, particularly to operators who aren’t careful. Thorough training is usually required of all researchers who are going to be using this and other related equipment.

There are usually a couple of different ways to break composite materials down into their individual components, but centrifuge spinning is often a preferred method in many of the research sciences. Spinning compounds around a fixed axis while applying a perpendicular force uses physics to isolate particulates and essentially spin things apart into their molecular components. Simple liquids and solutions will often separate in a standard centrifuge, which is a staple in many physics and chemistry classrooms. An ultracentrifuge works the same way, but typically spins much faster and more forcefully, which makes it suitable for more complex compounds and substances. These “ultra” varieties are most common in pharmaceutical research and development, and are also used in many engineering, often where chemical and environmental applications are concerned.

A preparative ultracentrifuge is usually the most common type in labs and research centers. It is used to isolate specific particles for reuse and is considered to be a high-performance instrument that is reliable and efficient, and operates quickly and quietly. It features a variety of rotors that are suitable for a range of separation tasks used in cell biology, biochemistry, and molecular biology. A sample can be spun at a high speed until its components separate, at which time they can then be isolated, measured, and studied further. Most preparative units include automatic rotor-life management, a color LCD screen, and positive-feedback capabilities. Many are also able to digitally transfer results to computers and smartphones.

Analytical centrifugation is another possible use for these sorts of tools. This techninque measures the physical properties of sedimenting particles and the way they behave in a solution state. Theodor Svedberg invented the analytical version of this tool and won the Nobel Prize in Chemistry for the research he conducted with it. It’s most common in biomedical research.

In analytical scenarios, samples are centrifuged in a cell, and an optical system projects an image of the cell on a computer or film in real time. The most common types of analytical-based experiments are those in sedimentation velocity and equilibrium, which offer information about the shapes, sizes, and conformational changes of macromolecules.

There are dangers associated with the use of an ultracentrifuge because it operates at very high speeds and often uses solutions that involve harsh chemicals. Both of these factors create mechanical stress that can cause rotors to wear out. In addition, rotors must be loaded and balanced correctly or they can break loose, causing significant damage, injury, and even explosion. Each instrument should receive regular maintenance, and users should be properly trained to load and balance it correctly. Regular cleaning of the rotors is also recommended, for safety as well as accuracy.