The Design of Labotatory Centrifuge
Published:10-03-11 09:25 write:kd Click:
The Design of Labotatory Centrifuge
Laboratory centrifuges are used in chemistry, biology, and biochemistry for isolating and separating solids from liquids in a suspension. The solids can be insoluble compounds, biomolecules, cell organelles, or whole cells. They vary widely in speed and capacity. They usually comprise a rotor containing two, four, six, or many more numbered wells within which centrifuge tubes may be placed.
When a suspension in a centrifuge tube is centrifuged, the solids settle at the bottom of the centrifuge tube; having a tapered wall helps to concentrate the solids, making it easier to decant the supernatant solution, leaving the solids.
Generally spoken, there are two main types of rotors:
Fixed-angle rotor
The rotor (mainly made of aluminium) is very compact. There are boreholes with a specific angle (like 45°) within the rotor. These boreholes are used for the sample tubes.
Swing-out rotor (= horizontal rotor)
The rotor looks like a cross with gondolas, called buckets. Within these buckets, different tubes can be centrifuged. For a safe centrifugation, a specific adadpter for every tube shape is mandatory.
The rotor is closed by a rotor lid. The rotor is located in a rotor chamber which is covered by a metall centrifuge lid. The open lid prevents the motor from turning the rotor when the rotor chamber is open. During the run, the lid is locked. The lid protects the user from being injured by touching a rapidly spinning rotor. The rotor chamber and the lid of high quality centrifuges are robust enough to survive a rotor failure at full speed. This robustness protects the user and the laboratory from crashing fragments in case the rotor fails catastrophically. After a rotor crash, a centrifuge should not be reused as the enormous forces during a crash may have damaged essential parts of the device.
The rotor must be balanced by placing samples or blanks of equal mass opposite each other. Since most of the mass is derived from the solvent, it is usually sufficient to place blanks or other samples of equal volume. As a safety feature, some centrifuges may stop turning when wobbling is detected.
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