Precautions for the use of laboratory centrifuge
After you have a reliable machine, you must strictly follow the necessary precautions to make it work better. In the so-called iron-battled soldiers, students in the laboratory come in batches and graduate, and special training is required to reduce accidents. I remember many years ago, the big centrifuge loaned by the World Bank in the school broke down. Please foreigners to repair it. Look at the stains on the wall of the centrifugal chamber. The grass or rubber pads used for temporary balancing in the individual rotor holes. Casually, the foreigner murmured—it is hard to believe that graduate students from famous Chinese universities did this experiment. Similar words have been heard many times after several years, such as an automatic sequencing needle sampler sent by Shanghai for maintenance-the thin metal needles to be sampled should be soaked and cleaned, but sterilized by fire- The needles were blocked, or were artificially twisted or broken, some people asked at the time-this is the best school, the best laboratory, the best students you have used in China? Every time I hear it, I feel the same. In fact, the damage to many instruments is simply because we are afraid of trouble, sloppy or want to save something-maybe there was no immediate problem at the time, but the damage accumulated little by little. Every student is stricter, not only can reduce unnecessary damage, but also make the experiment a lot smoother.
1. The loading and balancing of the sample due to the centrifugal force generated during centrifugation. When the sample carried by the rotor is unbalanced, a large torque will be generated. The lighter one will cause the machine to tremble and vibrate, and the heavy one will twist the shaft to cause an accident. Therefore, the balanced loading of centrifuged samples is a special issue. The higher the centrifugal speed, the higher the requirements for balance. In addition to the softer centrifuge with a certain adjustment ability to allow visual balance, all centrifuges are required to balance the sample with a balance. The centrifuge tubes must be at least symmetrically balanced in pairs, or symmetrically balanced in batches of three, preferably the same weight. Do not idle the horizontal rotor. When balancing, it is necessary to ensure that the symmetrical two-tube samples have the same weight, and that the density and volume of the two samples are equal. Because the torque generated during centrifugation is not only related to the weight of the sample, but also to the radius of rotation of the sample. For example, although a pipe of water and half pipe of sand have the same weight, the radius of rotation of the half pipe of sand is larger, so the torques are very different, and the rotation is not balanced. Therefore, two centrifuge tubes in a symmetrical position must be loaded with samples of similar density. For example, to centrifuge two samples at the same time, one tube is diluted with distilled water and the other tube is prepared with 60% sucrose. Although the weights of the two tubes are equal, they cannot be paired into a pair of centrifuges. Instead, a tube of water and a tube of 60% sucrose must be installed as counterweights, or they will not work properly.
2. The storage and use of the rotor must strictly follow the instructions.
3. The selection of centrifuge tubes should refer to the instructions and materials of the centrifuge tubes to prevent rupture due to improper use, not only the loss of samples but also contamination of the rotor and centrifuge. In order to reduce the resistance during ultracentrifugation, they are all operated under vacuum. Therefore, in addition to stainless steel and thick-walled polycarbonate (PC) centrifuge tubes, the sample must be filled, otherwise the centrifuge tubes will be deformed or broken due to vacuum. Normal high-speed or low-speed centrifugation should not be filled. All covered rotors, horizontal baskets, and test tube caps should be tightly closed to prevent sample leakage and loss of balance. When using the angle rotor, it is necessary to cover the rotating head cover, otherwise there will be a large eddy current resistance and frictional heating in the centrifugal cavity, which is equivalent to adding an extra burden to the motor and the refrigerator of the centrifuge and affecting the service life of the centrifuge.
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