Centrifuge working principle introduction and purchase considerations

Centrifuges are essential equipment for laboratory and clinical medicine, but many laboratories tend to focus on analytical clinical testing while ignoring basic equipment. Centrifuge is one of the basic equipment commonly used by Zui. It is widely used in hospital laboratories, centrifuges to separate serum, precipitate tangible cells, concentrate bacteria, PCR tests and other essential tools.

First, the working principle of the centrifuge

During the high-speed rotation of the centrifuge, the movement caused by the centrifugal force causes the solid matter suspended in the liquid to form a sediment, that is, the mass or volume of the suspended body fluid moves to a large radius of the rotor radius, and the mass Or a smaller portion is deposited near the radius of the rotor. Above we mentioned the concept of centrifugal force. Centrifuge is a machine that generates centrifugal force. The centrifugal force is related to rotor radius, rotation speed and sample quality: F=Rmω2 (F: centrifugal force: R: radius: m: sample mass: w: rotation speed). Centrifugal force is important for measuring centrifuge One of the parameters is also one of the different criteria for the grade of the centrifuge. The centrifuge will give the large speed and centrifugal force of the centrifuge when it leaves the factory. We all know that the radius of the rotor and the quality of the sample are constant during operation. Only the speed can be changed by control, so we tend to use the speed to describe a centrifuge. Such as: high-speed centrifuge, ultra-high speed centrifuge.

Second, the classification of centrifuges:

1, according to the size of the speed can be divided into: low-speed centrifuge, high-speed centrifuge and ultra-high-speed centrifuge;

2, according to the requirements of temperature can be divided into: ordinary centrifuge and refrigerated centrifuge;

3, according to the different rotors: horizontal rotor centrifuge and angle rotor centrifuge;

4, according to the size of the centrifuge can also be divided into: floor-standing centrifuge, desktop centrifuge, handheld centrifuge, etc.;

5, according to the grade of the centrifuge can also be divided into ordinary centrifuges and precision centrifuges.

Ordinary centrifuges do not have many functions, and are not accurate in terms of speed and capacity. For example, the large speed of a common centrifuge is 5000 rpm, but the actual speed cannot reach 5000 rpm. Such a centrifuge is only suitable for ordinary centrifugation work, such as separating serum, concentrating urine, and the like. The precision centrifuge has many functions, accurate rotation speed and capacity, and is suitable for some experiments with high requirements on centrifuges, such as PCR experiments and separation of blood components (used in blood stations). Choose a common centrifuge, depending on the size of the workload, mainly from the two aspects of speed and capacity.

Third, the following details the problems that should be paid attention to when purchasing precision centrifuges:

(1) Speed:

The centrifuge is divided into a low-speed centrifuge (<10000rpm/min), a high-speed centrifuge (10000rpm/min-30,00000rpm/min), and an ultra-high-speed centrifuge (>30000rpm/min) according to the different speed of the Zui. Each centrifuge has a centrifuge. The rated zui high speed, zui large speed refers to the speed under no-load conditions, but the large speed of zui varies depending on 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 16,000 times per minute at no load. After adding the sample, the speed will definitely be less than 16000 rpm/min. Different rotors, zui large speed is also different (one imported centrifuge can be equipped with multiple rotors), the horizontal rotor can reach 5000rpm/min, but the angular rotor can reach 14000rpm/min. The specific difference should be consulted in detail. And the relevant technical personnel of the production plant, so the choice of the speed should be cautious, the Zui large speed of the selected centrifuge should be higher than the target speed. For example, the target speed is 16000 rpm/mIn, and the large 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 high temperature environment, which is to choose a refrigerated centrifuge, which has a rated temperature range. The heat generated by the centrifuge at high speed is balanced with the refrigeration system of the centrifuge at a certain temperature (the sample for general freeze centrifugation needs to be kept at 3 ° C ~ 8 ° C), and the specific amount can be related to the rotor, such as a centrifuge The rated temperature range is -10 ° C ~ 60 ° C, the horizontal rotor can be rotated to about 3 ° C when installed, if the angle rotor may only be about 7 ° C. This should also be consulted in detail about the product sales staff and the relevant technical personnel of the production plant.

(3) Capacity:

How many sample tubes need to be centrifuged each time, how much capacity is needed for each sample tube. These factors determine the total capacity of a centrifuge, simply the total volume of the centrifuge = the capacity of each centrifuge tube × the number of centrifuge tubes, total The size and workload size are matched.

(4) Rotor:

The rotor of the centrifuge is mainly divided into two types: the horizontal rotor: the running blue is in a horizontal state during operation, and is at right angles to the rotating shaft. The sample concentrates the sediment on the bottom of the centrifuge tube: the angle rotor: the centrifugal container forms a fixed angle with the rotating shaft, and the sample will precipitate. Focus on the bottom of the tube and the side wall near the bottom. If you want the separated sample to be concentrated at the bottom of the centrifuge tube, select the horizontal rotor. If you want the sample to concentrate on the bottom of the centrifuge tube and the side wall near the bottom, select the angle rotor. There are also special tests or special samples that require special rotors such as large-capacity baskets (used for blood stations), ELISA plate rotors, slide rotors, PCR rotors, test tube rotors, and capillary rotors. The rotor has a fixed size, which is combined with the capacity of the centrifuge, such as the 36 × 5ml angle rotor, which determines the type of rotor and determines the capacity of the centrifuge, so the choice of the rotor is very important.

(5) Control system:

High-end centrifuges use a microcomputer control system that not only ensures safe operation of the centrifuge but also automates tasks. Now many centrifuges have a better humanized control system. For example: rotor identification function, safety lock function, fault prompt function, acceleration and deceleration curves, and so on.

In addition to the above points, pay attention to some details and necessary accessories. The main component of the centrifuge is the motor. The motor is divided into a carbon brush motor and a carbonless brush motor. The former has been eliminated. Most of the current centrifuges are brushless motors, and some motors also have a brake function. Refrigerated centrifuges also differ in terms of refrigeration, and now environmentally friendly technologies are of course fluorine-free refrigeration. In addition to this, consider the noise problem and try to choose a quieter centrifuge to maintain a comfortable experimental environment. Care should be taken in the accessories. In some experiments, special centrifuge tubes (centrifugal toxic samples or samples requiring ultra-high-speed centrifugation) should be used. Such centrifuge tubes must be equipped with corresponding sleeves for safety. There are also some special sample containers (irregular vials, blood bags, etc.). These details and accessories must be carefully considered when selecting a centrifuge, otherwise normal operation will not be possible. The price of the three centrifuges is quite different between the domestic centrifuge and the imported centrifuge. The inlet of the centrifuge with the same function is about 3 times that of the domestic one. There are also differences in the price of domestically-grade centrifuges, which are mainly distinguished by product performance and material selection. Also related to the manufacturer's research and development strength. In terms of performance, centrifuges with refrigeration are much more expensive than normal, and the more control programs and functions, the higher the price of the centrifuge. The difference is the configuration aspect, sometimes the price of the attachment will be higher than the price of the host. When purchasing, be careful to select the rotor (quantity and type) in addition to the main unit, plus the necessary centrifuge tubes, sleeves, special centrifuge bottles or blood bags.

(Source: HC Pharmaceutical Industry Network)

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