Laboratory infrastructure is the necessary equipment for scientific research and clinical medicine, but many laboratories tend to focus on analytical clinical testing and ignore the infrastructure.
Centrifuge is one of the most commonly used basic equipment in the hospital laboratory is very widely used, centrifuges are very separate from the serum, precipitation of tangible cells, concentration of bacteria, PCR tests and other essential tools.
One, centrifuge working principle
Centrifuge in the process of high-speed rotation, the centrifugal force caused by the movement of the solid material suspended in the liquid to form a precipitation, that is, the suspended body fluid in the mass or volume of the larger objects to the direction of the largest radius of the rotor head to move, while the mass or volume of the smaller part of the deposit in the rotor radius of the head of the place closer to the radius.
Above we mentioned the concept of centrifugal force. A centrifuge is a machine that generates centrifugal force, which is related to the radius of the rotor, the rotational speed and the mass of the sample: that is, F=Rmω2 (F: centrifugal force: R: radius: m: mass of the sample: to: rotational speed), the centrifugal force is one of the most important parameters of centrifuges, and also one of the differentiation criteria of the centrifuges, centrifuges in the factory will be given the maximal centrifugal force of the centrifuge.
We all know that the radius of the rotor and the sample mass in the operation of the time is unchanged, only the speed can be changed through the control, so we are often accustomed to use the speed to describe a centrifuge. For example: high-speed centrifuge, ultra-high-speed centrifuge.
Second, the classification of centrifuges
There are many types of centrifuges, we are accustomed to the following aspects of classification: according to the size of the rotational speed can be divided into: low-speed centrifuges, high-speed centrifuges and ultra-high-speed centrifuges: in accordance with the requirements of the temperature can be divided into: ordinary centrifuges and freezer centrifuges: according to the rotor of the different types of centrifuges are divided into: the horizontal rotor centrifuge and the angular rotor centrifuges according to the size of the centrifuge The size of the volume can also be divided into: floor-standing centrifuge, desktop centrifuge, palm centrifuge, etc.: according to the grade of the centrifuge can also be divided into ordinary centrifuge and precision centrifuge. Ordinary centrifuges do not have many functions and are not precise in terms of speed and capacity, for example, the maximum speed of an ordinary centrifuge is 5000 rpm, but the actual speed cannot reach 5000 rpm. Such centrifuges are only suitable for ordinary centrifugal work, such as: separating serum, concentrating urine and so on.
Precision centrifuges are multi-functional, accurate in speed and capacity, and are suitable for some experiments with higher requirements for centrifuges, such as: PCR experiments, separation of blood components (mostly used in blood stations) and so on.
The purchase of ordinary centrifuges, according to the size of the workload, mainly from the speed and capacity of the two aspects of choice. The following is a detailed introduction to the purchase of precision centrifuges should pay attention to:
(1) speed: centrifuges are divided into low-speed centrifuges (<1 0000 rpm/min), high-speed centrifuges (1 0000 rpm/min a 30,000 rpm/min), ultra-high-speed centrifuges (>30,000 rpm/min), according to the maximum speed of the different. Each centrifuge has a rated maximum speed, which refers to the speed at no load, but the maximum speed varies according to the type of rotor and the size of the sample mass. For example: the rated speed of a centrifuge is 16000 rpm/min, which means that the rotor rotates 16000 times per minute under no load, and after adding the samples, the speed will be less than 16000 rpm/min. The maximum speed is also different depending on the rotor (an imported centrifuge can be equipped with several rotors), and the horizontal rotor can reach 15000 rpm/min, but the angular rotor can reach about 14000 rpm/min. Can reach about 14000 rpm/min, the specific difference to consult the product sales staff and the relevant technical personnel of the production plant, so be careful in the choice of speed, the maximum speed of the selected centrifuge should be higher than the target speed. For example, if 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, which requires the selection of a refrigerated centrifuge, which has a rated temperature range. Centrifuge in the high-speed operation of the heat generated by the centrifuge and the centrifuge refrigeration system balanced at a certain temperature (generally frozen centrifugal samples need to be maintained at 3 ℃ ~ 8 ℃), how much can be achieved specifically and rotor-related, such as a centrifuge rated temperature range of -10 ℃ ~ 60 ℃, loaded with a horizontal rotor in the rotation of the time can be reached around 3 ℃, if it is a corner rotor may be only to 7 ℃ or so. This point should also be detailed consultation with the product sales staff and production plant of the relevant technical staff.
(3) capacity: how many sample tubes need to be centrifuged each time 7 how much capacity is needed for each sample tube 7 these factors determine the total capacity of a centrifuge, simply put the total capacity of the centrifuge = the capacity of each centrifuge tube × the number of centrifugal tubes, the total capacity and workload size is matched.
(4) rotor: the rotor of the centrifuge is mainly divided into two kinds, horizontal rotor: when running hanging blue in a horizontal state, and the rotor axis at right angles, the sample will be precipitation concentrated in the bottom of the centrifuge tube: Angle rotor: centrifugal containers and the rotor axis into a fixed angle, the sample will be precipitation concentrated in the bottom of the centrifuge tube and the side wall near the bottom. Choose the horizontal rotor if you want the separated sample to be concentrated at the bottom of the centrifuge tube, or the angular rotor if you want the sample to be concentrated at the bottom of the centrifuge tube and on the sidewalls near the bottom.
There are also some special tests or special samples require special rotors such as: large-capacity basket (mostly used in blood stations), enzyme plate rotor, slide rotor, PCR rotor, test tube rack rotor and capillary rotor. The rotors all have fixed specifications, which are combined with the capacity of the centrifuge, such as 36 × 5 ml corner rotor, which determines both the type of rotor and the capacity of the centrifuge, so the choice of rotor is very important.
(5) control system: high-grade centrifuges have adopted a microcomputer control system, these control systems can not only ensure the safe operation of the centrifuge can also automatically complete the work task. Now many centrifuges have a better humanized control system. For example: rotor recognition function, safety lock function, fault indication function, acceleration and deceleration curve and so on. In addition to the above points should also pay attention to some details and necessary accessories. The main part of the centrifuge is the motor, the motor is divided into carbon brush motor and brushless motor, the former has been eliminated, most of the centrifuges are now brushless motor, some motors also have a brake function. Refrigerated centrifuges are also different in terms of refrigeration, now the environmentally friendly technology is of course fluorine-free refrigeration. In addition to this, you should also consider the noise problem, try to choose the centrifuge with less noise, so as to maintain a comfortable experimental environment. In the accessories should also be careful, some experiments with special centrifuge tubes (centrifugation of toxic samples or need to ultra-high-speed centrifugation of samples), such centrifuge tubes must be equipped with the appropriate tube sleeve, in order to be more secure. There are also some special sample containers (irregular sample bottles, blood bags, etc.), these details and accessories should be considered carefully when choosing a centrifuge, otherwise it will not be able to carry out normal work.
Three centrifuge prices
Domestic centrifuges and imported centrifuges are very different, the same function of the centrifuge imported is about 6 to 10 times more than the domestic, mainly because of the durability of the imported centrifuges, the control of the temperature and speed is more precise, the same grade of centrifuges are not very big price differences between each other, the main distinction between the performance and configuration.
The difference between the mainframe is in the performance, with frozen centrifuges to be much more expensive than ordinary ones, some centrifuges also have a heating function, the more control programs the higher the price of the centrifuge. The larger the difference is in the configuration, sometimes often the price of accessories will be higher than the price of the host. Selection should be noted that, in addition to the host, the choice of rotors (number and type), plus the necessary centrifuge tubes, tube sets, special centrifuge bottles or blood bags, all of which add up to the price of a complete centrifuge.