A centrifuge is a special instrument that separates and precipitates a mixture (containing solids) by centrifugal force. Commonly used electric 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 widely used, which is an essential tool 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.
1 The precipitate is sticky or the mother liquor is viscous.
2 The precipitated particles are small and easy to pass through the filter paper.
3 The amount of precipitation is too much and loose.
4 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.
5 Precipitate and mother liquor must be separated quickly.
6 general colloidal solution.
1. Basic structure and performance of electric centrifuge
1 Ordinary (non-frozen) centrifuges are simple in structure, can be divided into small desktop and floor type, equipped with drive motor, governor, timer and other devices, easy to operate. The speed of the low-speed centrifuge generally does not exceed 4000 rpm, and the high speed of the desktop high-speed centrifuge can reach 18000 rpm.
2 The speed of the low-speed refrigerating centrifuge is generally not more than 4000 rpm, and the large capacity of Zui is 2-4 L. It is a laboratory used for a large number of primary separation and extraction of biological macromolecules and sediments. The rotor is mostly made of aluminum alloy, flat and angled. The centrifuge tube has various types of hard glass, polyethylene hard plastic and stainless steel tube. The centrifuge is equipped with a drive motor, timer, adjuster (speed indication) and refrigeration system (temperature adjustable range -20-+40 °C), which can be changed according to the needs of centrifugal materials. .
3 High-speed refrigerated centrifuges can reach speeds above 20,000 rpm. In addition to the performance and structure of low-speed refrigerated centrifuges, the angle rotors used in high-speed centrifuges are made of titanium alloy and aluminum alloy. The centrifuge tube is a polyethylene hard plastic product with a cover. Such centrifuges are often used to collect microorganisms, cell debris, cells, large organelles, sulfate precipitates, and immunoprecipitates.
4 The speed of the ultracentrifuge can reach more than 50,000 rpm, which can separate the subcellular organelles and measure 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, it is equipped with a cooling drive motor system (air-cooled, water-cooled), a speed limiter, a chronograph, a speed recorder, and the like. In addition, the ultracentrifuge is equipped with an evacuation system.
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