Centrifuge tube automatic production line - three centrifugation methods

　　Centrifuge tube automation production line solution manufacturers know three commonly used centrifugation methods: differential centrifugation; rate zonal centrifugation; isopycnic zonal centrifugation.

　　1. Differential centrifugation method

　　Differential centrifugation is often used in the extraction of crude products of biochemical samples. The difference in the sedimentation coefficient of different suspended particles in the centrifugal force field is used. Under the same centrifugal condition, different particles have different sedimentation velocities. By continuously increasing the relative centrifugal force, a non-uniform mixed liquid Particles of various sizes and shapes in the dispersed system settle in layers.

　　During the operation, the supernatant and the precipitate are generally separated after the first stage of centrifugation, and then the supernatant is centrifuged at a higher speed to separate the second part of the precipitate, and the speed is increased step by step in this way. The desired material is isolated. The resolution of differential centrifugation is not high, and various particles with sedimentation coefficients in the same order of magnitude are not easy to separate, so it is often used for crude product extraction of biochemical samples.

　　2. Velocity zone centrifugation

　　Velocity zonal centrifugation is an incomplete sedimentation separation. The sedimentation effect is greatly affected by the physical scale of the substance itself. It is generally used in the case where the materials have different sizes but the same density. It means that according to the centrifugal force of the particles to be separated, Due to the difference in the sedimentation velocity in the gradient liquid, the particles with different sedimentation velocities are in different density gradient layers after centrifugation, forming several separate sample zones to achieve the purpose of separation from each other.

　　For example, to separate mononuclear cells from venous blood, the former separation fluid Ficoll divides all mononuclear cells (lymphocytes and monocytes) in the blood into one layer and extracts them at the same time. The Percoll separation fluid divides the lymphocytes and monocytes in the blood into two gradient layers and extracts them separately. The gradient solution acts as a support medium and stabilizer during and after centrifugation to avoid resuspension of layered particles caused by mechanical vibration.

　　When using the rate zonal centrifugation method, the centrifugation time needs to be strictly controlled, not only to have enough time for various particles to form a zone in the medium gradient liquid, but also to avoid any particle to be separated from forming a precipitate state.

　　3. Isodensity zonal centrifugation

　　Isodensity zonal centrifugation means that when there is a difference in buoyancy density of different particles in the liquid dispersion system, under the centrifugal force field, the particles either settle down or float up, and move along the gradient to the position where their densities are exactly equal, that is, equal Density points, centrifugation method to form zones.

　　The centrifugation effect of isopycnic zonal centrifugation depends on the buoyant density difference of the particles. The larger the density difference, the better the separation effect, regardless of the size and shape of the particles, but the latter two determine the speed, time and zone of equilibrium. width.

　　The characteristics of the isopycnic zonal centrifugation method: It is related to the density of the sample particles; it has nothing to do with the size of the sample particles and other parameters; if the rotation speed and temperature remain unchanged, even if the centrifugation time is prolonged, the banding positions of these particles cannot be changed.