How are centrifuges classified?

Release Time: 2022-08-25

There are many types of centrifuges on the market, so how do we distinguish them?

According to the speed, they can be divided into low-speed centrifuges, high-speed centrifuges, and ultra-high-speed centrifuges.

● Low-speed centrifuge (<10000 rpm)
● High-speed centrifuge (10000-30000 rpm)
● Ultra-high-speed centrifuge (>30000 rpm)

According to temperature requirements, they can be divided into: ordinary centrifuges and refrigerated centrifuges.

● Ordinary centrifuge
● Refrigerated centrifuge

According to different rotors, they can be divided into horizontal rotors and angle rotors.

● Horizontal rotor: When rotating, the swing bucket is in a horizontal state, at a right angle to the rotating shaft, and the sample will precipitate and concentrate at the bottom of the centrifuge tube.

Main characteristics of horizontal rotor:

● When the rotor is stationary, the centerline of the centrifuge tube in the rotor is parallel to the rotating shaft;
● When the rotor rotates and accelerates, the centerline of the centrifuge tube gradually transitions from a parallel position to a vertical position, i.e., at a 90° angle to the rotating shaft;
● The direction of particle sedimentation is basically consistent with the direction of the radius of rotation, with a small amount of "wall effect"
● The center of gravity of the rotor is higher
● The distance that the sample particles settle through the solvent layer is greater than the tube diameter
● Particularly effective for separating samples with multiple components
● Commonly used for rate zonal centrifugation and isopycnic centrifugation

Main application scenarios of horizontal rotor:

● High sample throughput
● Gradient centrifugation is required
● Need to centrifuge the sample to the middle of the bottom of the tube
● Need to centrifuge various centrifuge tubes, bottles, and work plates. Such as: cell collection, blood cell separation, collection of supernatant from large-throughput culture, crude purification of protein samples, etc.

Angle rotor: The centrifuge container is at a fixed angle to the rotating shaft, and the sample will precipitate and concentrate at the bottom and near the bottom side wall of the centrifuge tube.

Characteristics of angle rotor

● "Wall effect": There is a certain angle. During centrifugation, particles hitting the outer wall of the centrifuge tube slide down the wall to the bottom of the tube to form a precipitate. This effect makes the final precipitate at the bottom of the tube more compact.
● Low center of gravity, higher speed
● The distance that the sample particles pass through the solvent layer is slightly larger than the diameter of the centrifuge tube;
● Limited centrifugation throughput. The maximum centrifugation throughput of a benchtop centrifuge is 6x250ml, and the maximum centrifugation throughput of a floor-standing high-speed centrifuge is 6x1L.

Main application scenarios of angle rotor:

● Requires greater relative centrifugal force for complete separation
● To obtain a more compact precipitate
● Small sample volume, such as high-speed centrifugation of nucleic acids, precipitation of bacteria, etc.

About the material of the rotor
Aluminum: Lighter, weaker strength, suitable for use at lower speeds;
Stainless steel: Good strength, but the material itself is too heavy;
Titanium alloy: Good strength, and lighter than stainless steel;

Classification by temperature (refrigerated and ordinary)
Refrigerated type: In some experiments, it is necessary to ensure the biological activity . biological activity It is most active below 4 degrees. In order to maintain the temperature in the centrifuge chamber at 4 degrees, a centrifuge with a refrigeration function is required. Some substances may change their morphology at high temperatures, so centrifugation at a constant temperature will improve the accuracy of the experiment.

About centrifuge tubes suitable for centrifuges
When loading the solution, follow the specific operating instructions of various centrifuges, and select suitable centrifuge tubes according to the properties and volume of the liquid to be centrifuged. Some centrifuge tubes are lidless, and the liquid should not be filled too much to prevent it from being thrown out during centrifugation, causing the rotor to become unbalanced, rusty, or corroded. Preparative ultracentrifuge centrifuges often require the liquid to be filled to prevent the upper part of the plastic centrifuge tube from collapsing and deforming during centrifugation. Centrifuge tube materials include PP, PE, PC, glass, stainless steel, PA, and PF. The volume ranges from 0.2 to 500 ml.