Biopharmaceutical centrifuge (picture from the Internet)
The centrifuge is a sample analysis and separation instrument integrating mechanical, electronic, refrigeration, vacuum, material and other technologies. The centrifugal force field generated by high-speed rotation is a medical instrument for separating, concentrating and purifying substances with different precipitation coefficients. It is widely used in In biomedicine, petrochemical industry, agriculture, food hygiene and other fields, it uses the difference in precipitation speed of different substances in the centrifugal force field to achieve the analysis and separation of samples. Centrifuges are divided into three types: low speed, high speed, and overspeed according to the speed. There are two types of tabletop and vertical. The maximum speed of a low-speed centrifuge generally does not exceed 6000 rpm. It is mainly used for blood or cell preparation, separation of protein and enzyme precipitates. Since a sufficiently large centrifugal force field cannot be generated, the low-speed centrifuge cannot separate ultra-small particles (such as viruses , DNA molecules) and macromolecules, or density gradient centrifugation; high-speed centrifuges have a speed of 12000-28000 rpm, which can separate viruses, bacteria, nuclei, cell membranes, mitochondria, etc., as well as DNA preparation. Above 50,000 rpm, with optical instruments, it can be used for molecular weight determination, protein structure and aggregation state analysis, compound purity verification, etc.
In recent years, with the rapid development of microelectronic technology and machinery industry, centrifuges have greatly improved in performance and reliability. This article introduces some of the recent progress.
1. Advanced transmission technology reduces noise and vibration
Centrifuges were usually driven by t) C motors, and some were powered by high-pressure airflow. Because IX: The carbon brush and commutator of the motor are important factors that cause spark interference, noise and affect the life of the motor, so in recent years, more and more centrifuges have used variable frequency motors or brushless DC motors. The frequency conversion motor drive method not only saves the work of replacing the carbon brush and avoids the pollution of carbon dust, but also the frequency conversion speed regulation disturbance system is easier to realize the speed regulation under the microcomputer control, so that the braking and acceleration time is optimized, even when When the rotation speed is very high, the noise and vibration can also be minimized. In addition, the variable frequency drive mode can also save electrical energy. The position sensor or single-chip microprocessor of the Wuxi DC motor realizes the startup and regulation of the motor. Common IX: The wear resistance of the motor brush has also been greatly improved, and the life of some brushes can reach 4000 hours.
Some centrifuges are designed with friction-reducing components and stabilizer sleeves, and electric fast brakes in the transmission system, so that the centrifuge can increase the acceleration too much when it goes up and down, and smoothly pass the rotor's critical speed. The resulting system resonance is reduced to a minimum. The motor buffer base or suspension frame, elastic coupling, and sound wave suppression system are used to reduce noise and make the working environment more quiet and comfortable.
2. Microcomputer control and calculation system, the operation is extremely convenient
Control and calculation are generally carried out with a microcomputer. Users can easily select operating parameters as needed. Generally, there are more than nine types of acceleration curves for selection. It can store s2 or more application centrifugal programs. The CTR or LED display displays the pre-selected values â€‹â€‹and actual conditions of data such as speed, acceleration, centrifugal force value, rotor parameters, centrifugal chamber temperature, etc. at a glance, and all operating parameters are repeatable. Some centrifuges have RS232 standard interfaces for external computers to record, set or modify operating parameters from external computers. Some centrifuges can perform related calculations and conversions during rotor operation, such as automatic calculation of the relevant centrifugal force field (RCF) and speed reduction calculation to prevent the precipitation of cesium chloride (CsCI), automatic optimization and simulation of the best operating conditions. American BECKMAN company oPtima series analytical ultracentrifuge is equipped with an optical detection system, scanning the optical density of the sample during sample separation, especially suitable for: receptor / self receptor research, molecular weight determination, precipitation coefficient calculation, biological quality control
3. A variety of rotor series to meet different centrifugal operations
With the continuous expansion of the application field of centrifuges, there are hundreds of varieties of rotors in more than ten categories. Angle rotor, vertical rotor, swing rotor and roller rotor, as well as various test tubes and bracket series, can meet almost all centrifugal operations. In order to facilitate users and increase interchangeability, the ultra-speed centrifuge rotors of centrifuge manufacturers such as DHPONT and KNTRON can be used in common with BECKMAN rotors. The large-capacity centrifuge adopts the swing-out rotor wind hood to greatly reduce the wind resistance of the swing-out rotor during operation. Under the same motor power consumption, the rotor speed of the 6-liter capacity separation at a time is increased from 3200 rpm to 4200 rpm.
In addition to the use of plastic rotors in some desktop low-speed machines, centrifuges use super-hard aluminum alloys or titanium alloys as rotor materials. The new molding process adopts die forging and ultra-speed forming to refine the material grains and increase rotor strength. The cutting process uses five Surface machining center to improve machining accuracy and efficiency.
4. Small and efficient refrigeration and vacuum system
Many samples are sensitive to temperature and need to be separated at or below room temperature. High-efficiency fluorine-free refrigeration system, small size, low noise, without destroying the atmospheric ozone layer, can make the temperature range of the centrifuge room reach a 2o â„ƒ ~ +40 â„ƒ, soil 1 â„ƒ to reduce wind resistance to speed up to reach the highest working speed and speed up the cold rotor , To extend the life of the motor and ensure temperature control, ultra-speed centrifuges, some high-speed centrifuges and low-speed large-capacity centrifuges are equipped with a vacuum system. BECKMANJ2 series centrifuges are equipped with an automatic vacuum system with a vacuum of o.5 atmospheres. Desktop centrifuges also currently use semiconductor devices for refrigeration.
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