A centrifuge is a special instrument that separates and precipitates a mixture (containing solids) by centrifugal force. Commonly used electric low-speed centrifuges in the laboratory include low-speed, high-speed centrifuges and low-speed, high-speed refrigerated centrifuges, as well as overspeed analysis and preparation of dual-purpose refrigerated centrifuges. Among them, low-speed (including large-capacity) centrifuges and high-speed refrigerated centrifuges are the most widely used, and are essential tools for biochemical laboratories to separate and prepare biomacromolecules. In the course of the experiment, in order to separate the precipitate from the mother liquor, both filtration and centrifugation are often used.
However, the use of the centrifugation method is effective in the following cases.
The precipitate is sticky or the mother liquor is viscous.
The precipitated particles are small and easily penetrate the filter paper.
The amount of precipitation is too much and loose.
The amount of precipitation is small and needs to be quantitatively determined. Or the amount of mother liquor is small, and the loss should be reduced when separating.
The precipitation and mother liquor must be separated quickly.
General colloidal solution.
Basic structure and performance of electric low speed centrifuge
Ordinary (non-frozen) centrifuge
This type of low-speed centrifuge has a simple structure and can be divided into two types: small table and floor type. It is equipped with a drive motor, governor, Timer and other devices, and is easy to operate. The speed of a low-speed centrifuge generally does not exceed 4000 rpm, and the maximum speed of a desktop high-speed centrifuge can reach 18,000 rpm.
Rotate the speed control handle smoothly and slowly (about 1~2 minutes) to the required speed. After the speed is stable, start timing.
After centrifugation, slowly adjust the handle back to zero.
Low speed refrigerated centrifuge
The rotation speed is generally not more than 4000 rpm, and the maximum capacity is 2-4L. It is the most commonly used in the laboratory for the extraction of biological macromolecules and sediments.
Centrifugal centrifuges are often used to collect microorganisms, cell debris, cells, large organelles, sulfate precipitates, and immunoprecipitates.
The rotational speed can reach above 20,000 rpm. In addition to the performance and structure of the low-speed refrigerated centrifuge, the angle rotor used in the high-speed centrifuge is made of titanium alloy and aluminum alloy. The centrifuge tube is a polyethylene hard plastic product with a cover.
In addition, the ultracentrifuge is equipped with an evacuation system.
Overspeed low speed centrifuge
The rotation speed can reach 50,000 rpm or more, and the subcellular organelle can be fractionated and used for the measurement of the molecular weight of proteins and nucleic acids. The rotor is made of high-strength titanium alloy, and can be replaced with different capacity and different types of speed rotors as needed. There are two types of ultracentrifuge drive motors, one for the FM motor to directly increase the speed, and the other for the speed through the gearbox. In order to prevent the drive motor from generating heat during high-speed operation, a cooling drive motor system (air-cooled, water-cooled), a speed limiter, a chronograph, a tachometer, and the like are provided. cut the power.
Use the method to check if the low speed centrifuge speed control knob is at zero position, whether the outer sleeve is intact and the rubber pad is padded.
The rotating head is mostly made of aluminum alloy, flat and angled. The centrifugal tube has various types of hard glass, polyethylene hard plastic and stainless steel tube. The centrifuge is equipped with a drive motor, timer, regulator (speed indication) and refrigeration system (temperature adjustable range -20-40 ° C), which can be changed according to the needs of the centrifugal material, the rotor of different capacity and different speeds.
General Use Procedures for Low-Speed ​​Centrifuges Before the centrifuge can stop rotating its own hands, the cover can be opened and the centrifuged sample can be taken out.
Rinse the outer casing and rubber mat, and invert and dry for use.
If unbalanced, adjust the amount of buffered water or centrifuged material. Place the well-balanced sleeve in the symmetrical position of the centrifuge's turret. Remove the unused sleeve and cover the centrifuge lid.
Before centrifugation, transfer the centrifuged substance into a suitable centrifuge tube, the amount of which should be 1~2cm away from the heart tube to prevent it from being thrown out during centrifugation. The centrifuge tube is placed in the outer sleeve, and buffer water is injected between the outer sleeve and the centrifuge tube, so that the centrifuge tube is not easily damaged.
Take an outer casing (the inner centrifuge tube is inside) and balance it on the scale.
Turn on the power and turn on the switch. Check the brush and bearing wear of the motor once a year, and replace the brush or bearing if necessary. Note that the brush models must be the same. Clean the brush box and the surface of the commutator when replacing.
Molybdenum disulfide lithium base grease lubrication. The amount is generally 1/2 of the bearing clearance
The low speed centrifuge should be placed on a flat and sturdy floor or bench and no tilting is allowed.
Note that the new brush should fall freely into the brush box. The brush is required to match the outer circumference of the commutator. When the bearing is short of oil or dirt, it should be cleaned and refueled. The bearing should be smooth and slowly increase or decrease. After turning off the power, wait for the centrifuge to stop automatically. Do not force the centrifuge to stop by hand or other objects.
The centrifuge should be grounded to ensure safety.
After the centrifuge is started, if there is abnormal noise and vibration, the centrifuge tube may be broken or the weight of the two tubes in the relative position may be unbalanced.
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