Laboratory Biochemical Examination Centrifuge Operating Instructions

During the experiment, two methods—filtration and centrifugation—are available for separating the precipitate from the mother liquor. Under the following circumstances, the centrifugation method is more suitable.
(1) The precipitate is viscous.
(2) The precipitate particles are small and easily pass through filter paper.
(3) Excessive and loose precipitate.
(4) The amount of precipitate is very small and needs to be quantitatively determined.
(5) Adjust the mother liquor viscosity.
(6) The mother liquor volume is very small; during separation, losses should be minimized.
(7) The precipitate and the mother liquor must be separated promptly.
(8) General limb solution.
A centrifuge is a specialized instrument that uses centrifugal force to separate and precipitate mixed solutions. Here, we will only introduce benchtop low-speed centrifuges and floor-standing low-speed centrifuges used in biochemistry laboratories.
1. Operation:

Before use, first check whether the gear selector knob is at “0”. The outer casing should be intact and leak-proof, and a rubber pad must be placed at the bottom of the outer casing.
(2) Before centrifuging, first transfer the substance to be centrifuged into a centrifuge tube of appropriate size. The amount should not exceed two-thirds of the tube’s volume to prevent overflow. Place this centrifuge tube into the outer tube, and then add buffer water between the centrifuge tube and the outer tube.
(3) Place a pair of outer tubes (together with the centrifuge tubes) on a balance to achieve equilibrium. If they are unbalanced, adjust either the amount of contents in the centrifuge tubes or the volume of buffer solution added. During each centrifugation operation, it is essential to strictly adhere to the balancing requirements; otherwise, you could damage the centrifuge’s components or even cause a serious accident. You should be extremely vigilant.
(4) Place the two balanced tubes into the centrifuge in symmetrical positions, close the centrifuge lid tightly, and remove any unused centrifuge tubes.
(5) When starting up, first turn on the power switch, then slowly adjust the knob to gradually increase the speed. When stopping, first turn the knob to “0.” If the centrifuge is not going to be used further, unplug it. Only after the centrifuge has come to a complete stop automatically can you open the centrifuge lid and remove the sample. Under no circumstances should you use your hands to forcibly stop the centrifuge from rotating.
(6) After use, wash the rubber gasket in the sleeve clean and store it properly. Rinse the outer sleeve and place it upside down to allow it to dry.
2. Precautions:
(1) During centrifugation, if you hear an unusual noise, it may indicate that the centrifuge tube has cracked. You should immediately stop the centrifugation. If the tube has already broken, thoroughly rinse away any glass shards (but do not pour the shards down the drain). Then, replace the tube with a new one and repeat the centrifugation process as described above. If the tube hasn't yet cracked, you still need to rebalance it before proceeding with centrifugation.
(2) Organic solvents and phenols can corrode plastic sleeves, while salt solutions can corrode metal sleeves. If any leakage occurs, the leaked solution must be promptly wiped clean, and the sleeve should be replaced immediately.
(3) Avoid prolonged continuous use. Generally, large centrifuges should be run for 40 minutes followed by a 20- or 30-minute break, while small benchtop centrifuges should be run for 40 minutes followed by a 10-minute break.
(4) The power supply voltage must match the voltage required by the centrifuge. Only after connecting the grounding wire can the centrifuge be powered on and used.
(5) The brushes and commutator of the motor inside the centrifuge should be inspected once a year. If wear is severe, replace the brushes or bearings.

For routine biochemical tests, use a low-speed centrifuge to separate the serum; the rotation speed should be around 3,000 to 5,000 rpm. Typically, this process takes no more than 3 minutes.