Care and maintenanceĬentrifugation lore includes tales of violent malfunctions resulting in total destruction of the unit and much of the surrounding lab space. “There is quite a range of options within different markets,” says Hugh Tansey, global commercial director for centrifugation at Thermo Fisher Scientific (Waltham, MA). Hence the capability overlap among various models. Vendors strive to address as many centrifugation tasks and container options as possible within specific centrifuge designs. Agilent’s (Santa Clara, CA) microplate centrifuges integrate with plate handlers and other components to automate complex workflows. Within these two basic designs, centrifuges accommodate a wide range of sample holders, including microtubes (1-2 mL in size) conical tubes (50-500 mL) larger containers for blood, plasma, and industrial processes and even microplates. In swinging bucket designs, as the centrifuge reaches terminal speed, samples swing out from a vertical position to where they become parallel to the floor or workbench pellets collect neatly at the bottom of the tube. In the former, sample tubes remain in a fixed position on the rotor within x-y-z space separations progress along the side of the tube and into a pellet at the bottom, depending on the actual angle. The two most common designs are fixed angle and swinging bucket. Numerous rotor types are available for laboratory centrifugation. Rotational speed is no indication of an application’s “sophistication.” Scientists employ relatively low-speed centrifugation (around 300 g) to isolate highly stress-sensitive stem cells and spinning rates of 1 million g to fractionate DNA, RNA, viral particles, and proteins. “But g-force is the more critical number.”
Rpms are also the most common feature users ask for, according to Peter Will, product manager at Labnet International (a Corning Life Sciences company Edison, NJ). Speed in rpms is the most common way to classify a centrifuge, although RCF (relative centrifugal force, or g) is more precise. As rotational speed increases, samples and analytes tend to get smaller and separations more difficult. At the very highest end are ultracentrifuges capable of separating molecules, cellular components, even isotopes. Speed (or g-force) refers to the centripetal force applied to the sample and varies significantly depending on the sample. Size may be further differentiated by unit size, rotor capacity, or sample size. Thus, for a given rpm value a centrifuge with a 12-inch radius will be twice as efficient as one with a six-inch radius, and for a constant radius a device spinning at 1,000 rpm is four times as effective as one rotating at 500 rpm.Ĭentrifuges may be broken down by size, speed, or application. Purchasing and Caring for a Lab Essential Air-cooled Benchtop Centrifuge / Allegra X-5 Beckman Coulter / Superspeed Centrifuge / Sorvall LYNX Thermo Fisher Scientific / Cell Culture Centrifuge Value Package Hettich / What’s important here is that centrifugation efficiency is proportional to the spinning radius and to the square of the angular velocity (radians per second, generally referred to as speed in revolutions per minute, rpm).
0 kommentar(er)
