Centrifuge is widely used in the chemical, petroleum, food, pharmaceutical, mineral processing, coal, water treatment and shipbuilding sectors. 1. Centrifuge classification
Centrifuges are mainly divided into filter centrifuges and sedimentation centrifuges.
The main principle of the filter centrifuge is to accelerate the liquid phase in the solid-liquid mixture out of the drum by the centrifugal force generated by the high-speed rotating centrifugal drum (with appropriate filter material), while leaving the solid phase in the drum. , To achieve the effect of separating solids and liquids, or commonly known as dehydration.
The main principle of the decanter centrifuge is to speed up the sedimentation speed of the different specific gravity components (solid phase or liquid phase) in the mixed liquid through the strong centrifugal force generated by the high-speed rotation of the rotor, and separate the substances with different sedimentation coefficients and buoyancy densities in the sample. 2. Laboratory centrifuge
The experimental centrifuge is an instrument that uses the centrifugal force generated by a rotating rotor to separate substances with different densities and different particle sizes in a suspension or emulsion, or analyzes at the same time as the separation.
Classification: Commonly used electric centrifuges in laboratories include low-speed, high-speed centrifuges, low-speed, high-speed refrigerated centrifuges, and ultra-speed analysis and preparation dual-use refrigerated centrifuges. Among them, low-speed (including large-capacity) centrifuges and high-speed refrigerated centrifuges are the most widely used. 2.1 Low speed centrifuge
Low-speed centrifuge is a conventional instrument used for centrifugal precipitation in the laboratory. It has the advantages of stable performance, flexible use, high reliability, and easy maintenance. It is widely used in clinical medicine, biochemistry, immunology, blood stations and other fields. The low-speed centrifuge has a simple structure and can be divided into two types: small desktop and floor type. It is equipped with a drive motor, a speed regulator, a timer and other devices, which is easy to operate.
The speed of the low-speed centrifuge generally does not exceed 4000rpm, the speed does not generally exceed 4000rpm, and the maximum capacity is 2-4L. The laboratory is most commonly used for the primary separation and extraction of large amounts of biological macromolecules and sediments.
Working principle of laboratory centrifuge
During the centrifugal operation, the centrifuge container containing the same amount of test wine is placed symmetrically in the hanging cup around the rotor, and the test wine is separated by the centrifugal force generated by the high-speed rotation of the motor and the rotor. The relative centrifugal force (RCF) depends on the radius of rotation of the sample during centrifugation and the speed n. Its calculation formula is as follows:
RCF=l.U8X10-5Xn2Xr (Xg) (1)
formula:
n means speed (r/min)
r Rotation radius (cm)
g-a unit of gravitational acceleration (9.8 Newtons/kg)
The time T required for the separation and precipitation of particles in the mixed wine is calculated by the following formula:
T=21. 4X(lnRmax-lnRmin)|^ (min) (2)
n2 r 2(0-P)
formula:
P mixed almost liquid density (g/cm3)
K-mixed wine viscosity (P)
n Speed (r/min)
r Rotor radius (cm)
. Particle density (g/cm3)
Rmax The horizontal distance from the bottom of the centrifugal test solution to the axis (cm)
Laboratory centrifuge operation and use process
The working table of the L tabletop high-speed centrifuge should be flat and firm, and the working room should be neat and clean, dry and well ventilated.
Check whether the speed control knob of the low-speed centrifuge is at the zero position, whether the outer tube is intact and has a rubber pad.
Open the centrifugal cover and wipe clean the inner cavity and rotor.
Transfer the centrifuged material into a suitable centrifuge tube, the amount should be 1~2cm away from the opening of the heart tube, so as not to be thrown out during centrifugation.
Place the centrifuge tube to be centrifuged on a platform scale to balance, and place the balanced test tube on the symmetrical position of the cross rotor of the centrifuge.
Close the cover and turn on the power.
Set the timing.
Select the centrifugal speed, after the centrifuge stops rotating by itself, open the cover to discharge the centrifuged sample.
Precautions for laboratory centrifuges
At present, electric centrifuges are commonly used in laboratories. The rotating speed of electric centrifuges is fast. Pay attention to safety. In particular, prevent the centrifuge from moving while working due to imbalance or aging of the test tube pad during the operation of the centrifuge. When the centrifuge tube was broken due to vibration when the centrifuge tube fell from the test bench or the lid was not covered, the glass fragments spun out, causing an accident. Therefore, when using the centrifuge, you must pay attention to the following operations:
(1) There is cotton or test tube pad at the bottom of the casing of the Gaoxin machine; always check the rotor and the centrifuge tube used in the experiment for cracks, aging, etc., if there is any connection, it should be replaced in time.
(2) If the electric centrifuge is noisy or the body vibrates, the power supply should be cut off immediately, and the fault should be eliminated in time.
Laboratory centrifuge maintenance
Do not place any material on the centrifuge cover. After each use, be sure to clean the inner cavity and rotor.
If the desktop high-speed centrifuge has not been used for a long time, the centrifuge cover should be opened for a period of time before use, and the inner cavity should be dried.
It is normal for the centrifuge to wear out after long-term use.
Leave the centrifuge tube promptly after use.
Basic knowledge of centrifuge
Centrifuge, according to the size of the workload, is mainly selected from two aspects: speed and capacity. The following is a detailed introduction to several common sense of centrifuges:
⑴ Rotation speed: The centrifuge is divided into low-speed centrifuge (.0000 rpm/min), high-speed centrifuge (1 0000 rpm/min-30000 rpm/min), and ultra-high-speed centrifuge (>30000 rpm/min) according to the maximum speed. , Each centrifuge has a rated maximum speed. The maximum speed refers to the speed under no-load conditions, but the maximum speed varies according to the type of rotor and the size of the sample. For example: the rated speed of a centrifuge is 16000 rpm/min, which means that the rotor rotates 16000 times per minute when there is no load. After adding the sample, the speed will definitely be less than 16000 rpm/mino. The maximum speed is also different (1) One imported centrifuge can be equipped with multiple rotors), the maximum speed of the selected centrifuge is higher than the target speed. For example: the target speed is 16000 rpm/min, the maximum speed of the selected centrifuge must be higher than 16000 rpm/min.
(2) Temperature: Some samples (such as proteins, cells, etc.) will be destroyed in a high-temperature environment, so you must choose a refrigerated centrifuge. The refrigerated centrifuge has a rated temperature range. When the centrifuge is running at high speed, the heat generated by the centrifuge is balanced with the refrigeration system of the centrifuge at a certain temperature (generally, samples for refrigerated centrifugation need to be kept at 3P~8°C). The specific amount is also related to the rotor, such as a centrifuge. The rated temperature range is -10P~60°C. When a horizontal rotor is installed, it can reach about 37% when it is rotating. If it is an angle rotor, it may only reach about 7P.
(3) Capacity: How many sample tubes need to be centrifuged each time? How much capacity does each sample tube need? These factors determine the total capacity of a centrifuge. Simply put, the total capacity of the centrifuge = the capacity of each centrifuge tube X the number of centrifuge tubes. The total capacity matches the size of the workload.
14) Rotor: There are two main types of centrifuge rotors. Horizontal rotor: The hanging basket is in a horizontal state during operation and is at right angles to the shaft. The sample concentrates the sediment on the bottom of the centrifuge tube: Angle rotor: The centrifuge container and the shaft are at a fixed angle , The sample concentrates the sediment on the bottom of the centrifuge tube and the side wall near the bottom. If you want the separated samples to concentrate on the bottom of the centrifuge tube, choose a horizontal rotor. If you want the sample to concentrate on the bottom of the centrifuge tube and the sidewall near the bottom, choose an angular rotor.
There are also some special tests or special samples that require special rotors, such as: large-capacity hanging baskets (mostly used in blood stations), enzyme plate rotors, glass slide rotors, PCR rotors, test tube rack rotors, capillary rotors, etc. The rotor has a fixed specification, which is combined with the capacity of the centrifuge, such as a 36X5 ml angle rotor, which determines the type of the rotor and the capacity of the centrifuge, so the choice of the rotor is very important.
⑸Control system: All high-end centrifuges adopt microcomputer control systems. These control systems can not only ensure the safe operation of the centrifuge, but also complete the tasks automatically. Many centrifuges now have better humanized control systems. For example: rotor identification function, safety lock function, fault prompt function, acceleration and deceleration curve, etc.
In addition to the above points, we must pay attention to some details and necessary accessories. The main component of the centrifuge is the motor. The motor is divided into a motor with a carbon brush and a brushless motor. The former has been eliminated. Most of the centrifuges now are brushless motors, and some motors also have a brake function.
Refrigerated centrifuges are also different in terms of refrigeration. The current environmentally friendly technology is of course CFC-free refrigeration. In addition, the noise problem must be considered, and try to choose a low-noise centrifuge, so as to maintain a comfortable experimental environment.
Be cautious in terms of accessories. Some experiments need to use special centrifuge tubes (centrifuge toxic samples or samples that require ultra-high-speed centrifugation). Such centrifuge tubes must be equipped with corresponding sleeves to be safer.
The difference between centrifuges for different experiments
①Ordinary (non-refrigerated) centrifuges This type of centrifuge has a relatively simple structure and can be divided into two types: small desktop and floor-standing. It is equipped with a motor, a speed regulator, a timer, etc., and is easy to operate. The speed of low-speed centrifuge generally does not exceed 4000rpm, and the maximum speed of table-top high-speed centrifuge can reach 18000rpm.
②The speed of low-speed refrigerated centrifuge generally does not exceed 4000rpm, and the maximum capacity is 2~4L. It is most commonly used in the laboratory for a large number of primary biological macromolecules, sediments, etc., respectively. Its turn
There are two types of centrifuge tubes, which are made of aluminum alloy, flat type and angle type, with hard glass, polyethylene hard plastic and stainless steel tubes. The centrifuge is equipped with a motor, a timer, and a regulator
(Speed indicator) and refrigeration system (temperature adjustable range is -20^+40seven), according to the need of centrifugal material, the rotor of different capacity and different type of speed can be changed.
®The speed of the high-speed refrigerated centrifuge can reach more than 20,000 rpm. In addition to the performance and structure of a low-speed refrigerated centrifuge, the angle rotors used in the high-speed centrifuge are all made of titanium alloy and aluminum alloy. The centrifuge tube is made of polyethylene hard plastic with a cover. This type of centrifuge is mostly used to collect microorganisms, cell debris, cells, large organelles, sulfuric acid precipitates, and immunoprecipitates.
@Ultracentrifuge rotation speed can reach more than 30,000 rpm, which can classify subcellular organs and be used for the determination of protein and nucleic acid molecular weight. The rotor is made of high-strength titanium alloy, which can be changed with different capacities and different types of speed rotors according to requirements. There are two types of ultracentrifuge motors, one is the direct speed-up of the frequency-modulated motor, and the other is the speed-up through the variable-speed gearbox. In order to avoid the heat generation of the motor during high-speed operation, a cooling motor system (air-cooled, water-cooled), speed limiter, timer, speed recorder, etc. are installed. In addition, the ultracentrifuge is also equipped with a vacuum system.
