Definition
A laboratory centrifuge is an instrumental device that uses centrifugal force to separate, purify, or analyze mixed samples. It drives the rotor to rotate at high speed, generating centrifugal acceleration much greater than gravity, causing particles or components of different densities in the suspension to settle or stratify along the radial direction, thereby achieving solid-liquid separation or liquid-liquid separation. This equipment is a general basic instrument in many scientific research and testing fields such as chemistry, biology, food, environment, and materials.
Principle
The working principle of laboratory centrifuges is based on centrifugal sedimentation. As the container containing the sample rotates around a central axis in the rotor, the particles in the sample are subjected to a combination of centrifugal force, buoyancy, and resistance. Particles denser than the medium settle outward radially, while particles with a density less than the medium move inward. The amount of centrifugal force depends on the rotational speed and the radius of rotation, and its calculation formula is:F = mω²r, among themFfor centrifugal force,mis the particle mass,ωis the angular velocity,ris the radius of rotation. Generally, centrifugal force is often expressed as relative centrifugal force, which is the ratio of centrifugal force to gravity:RCF = (1.118 × 10⁻⁵) × r × N², among themRCFThe unit is the multiple of gravitational acceleration,ris the radius (mm),Nis the rotational speed (rpm).
Measurement method
The key parameters of the centrifuge are usually measured and calibrated by the instrument built-in or external. The rotational speed can be obtained by monitoring the rotation frequency of the rotor by means of a photoelectric sensor or a Hall sensor. Temperature control is achieved by linking the temperature sensor installed near the rotor with the refrigeration system to ensure that the sample operates within the set temperature range. The relative centrifugal force is calculated from the rotational speed and the radius of rotation, and some models offer automatic conversion function. In addition, the running time is controlled by an electronic timer, which supports presets and real-time display. For analytical centrifuges, the sedimentation behavior of the sample during centrifugation can also be monitored in real time through the optical system to obtain particle distribution or molecular weight information.
Influencing factors
The centrifugal separation effect is influenced by a variety of factors. The rotational speed and relative centrifugal force directly determine the separation speed and resolution, which should be selected according to the characteristics of the sample. The rotor type and capacity affect the sample bearing mode and centrifugal efficiency, the angular rotor is suitable for high-speed operation, and the horizontal rotor is conducive to gradient separation. The characteristics of the sample itself, such as particle size, density difference, media viscosity, and initial concentration, can affect the sedimentation rate and separation purity. Temperature control is critical for heat-sensitive samples, and improper temperature can lead to sample denaturation or altered separation. The running time should be set to balance separation and efficiency, as too long may cause over-compaction or heat build-up of particles. In addition, the balanced state of the rotor and the symmetrical loading of the vessel are the basic conditions to ensure smooth and safe operation.
Application:
Laboratory centrifuges have a wide range of applications. In the field of biochemistry, it is commonly used for the separation and purification of cells, organelles, proteins, or nucleic acids. In environmental detection, it can be used for the collection and analysis of suspended solids and sediments in water bodies. In the food industry, it is used for oil separation, solids content determination or ingredient extraction. In materials science, it can be used for nanoparticle fractionation or composite material preparation. In addition, centrifuges are often used in various experimental scenarios such as blood typing (non-medical diagnosis), soil component separation, and solid-liquid separation after chemical reactions, making them a common tool for sample preparation and analysis.
Selection
When choosing a laboratory centrifuge, it is necessary to comprehensively consider the technical parameters and experimental needs. First, the conventional sample type and separation target were determined, and the required rotational speed and relative centrifugal force range were determined accordingly. For temperature-sensitive samples, attention should be paid to refrigeration capacity and temperature control accuracy. The rotor material and adapter type should be compatible with common vessel specifications, considering corrosion resistance. Capacity requirements depend on the number and volume of samples processed in a single process. The user-friendly design of the user interface, program storage function and maintenance convenience can improve the user experience. Safety features such as lid locks, imbalance detection, overspeed protection, etc. should also be evaluated. In addition, operating noise, footprint and energy consumption meet the requirements of the laboratory environment. The final selection should take into account safety, reliability and long-term cost while meeting the core separation performance.