Guide to Centrifuge Machine Types

Centrifuge machines can be categorized into industrial centrifuges and experimental centrifuges. Experimental centrifuges are divided into preparative centrifuges and analytical centrifuges. Preparative centrifuges are mainly used to separate various biological materials. The sample capacity of each separation is relatively large. Analytical centrifuges generally have optical systems. It is mainly used to study the physical and chemical properties of pure biological macromolecules and particles. According to the behavior of the substance to be tested in the centrifugal field (continuously monitored by the optical system in the centrifuge), the purity, shape and molecular weight of the substance can be inferred. Analytical centrifuges are all ultracentrifuges.

Preparative Centrifuge

• Ordinary centrifuge: the maximum speed of ordinary centrifuge is about 6000rpm; the maximum relative centrifugal force is nearly 6000xg; the capacity is tens of milliliters to several liters; the separation form is solid-liquid sedimentation separation; the rotor is angle type or outer swing type; and its rotation speed cannot be strictly controlled. Ordinary centrifuge usually doesn’t have a refrigeration system. It operate at room temperature, and is used to collect large particles that are easy to settle, such as red blood cells, yeast cells, etc. This centrifuge is mostly driven by an AC commutator motor, and the carbon brushes of the motor are easy to wear. Its speed is adjusted with a voltage regulator, the starting current is large, and the speed rises and falls unevenly. Usually the rotor is placed on a hard steel shaft, so it is extremely important to balance the centrifuge tube and contents accurately, otherwise the centrifuge will be damaged.
• High-speed refrigerated centrifuge: the maximum speed of high-speed refrigerated centrifuge is 20000-25000rpm (r/min); the maximum relative centrifugal force is 89000xg; the maximum capacity can reach 3 liters; and the separation form is also solid-liquid sedimentation separation. Its rotors are divided into various angle rotors, flat rotors, zone rotors, vertical rotors and large-capacity continuous flow rotors. Generally, there is a refrigeration system to eliminate the heat generated by the friction between the high-speed rotating rotor and the air. The temperature of the centrifugal chamber can be adjusted and maintained at 0-40°C, so the speed, temperature and time can be controlled strictly and accurately. High-speed refrigerated centrifuges have pointer or digital display, and are usually used for the separation and purification of microbial cells, cell debris, large organelles, sulfur press sediments, immunoprecipitates, etc. However, it cannot effectively sediment viruses, small organelles (such as ribosomes) or a single molecule.
• Ultracentrifuge: The rotational speed of ultracentrifuge can reach 50000-80000 rpm, and the relative centrifugal force can reach 1019000xg. The most famous manufacturers are Beckman of the United States and Hitachi of Japan. The centrifugal capacity ranges from tens of milliliters to 2 liters. The forms of separation are differential sedimentation separation and density gradient zone separation, and the allowable error of centrifuge tube balance is less than 0.1 g. The emergence of ultracentrifuges has brought new progress in the field of biological science research. Subcellular organelles that were only observed in electron microscopy in the past are fractionated by ultracentrifugation now. Ultracentrifuges can also separate viruses, nucleic acids, proteins, and polysaccharides.

Analytical Centrifuge

Analytical centrifuges use specially designed rotors and optical detection systems to continuously monitor the sedimentation process of substances in a centrifugal field, thus determine their physical properties.

The rotor of the analytical ultracentrifuge is elliptical to avoid stress concentrations in the holes. The rotor is connected to a high-speed drive through a flexible shaft. The rotor rotates in a refrigerated and vacuum chamber. The rotor has 2-6 small chambers for centrifuge cups. The centrifuge cups are sector-shaped quartz , and transmits light up and down. The centrifuge is equipped with an optical system that can monitor the sedimented material in the centrifuge cup through changes in UV absorption or refractive index during the entire centrifugation period, and can take pictures of the sedimented material during a predetermined period. When analyzing the sedimentation of substances in the centrifuge cup, the interface formed between the heavy particles and the light particles is like a refracting lens, resulting in a "peak" on the imaging bottom plate of the detection system. Due to the continuous sedimentation, the interface advances, so the peak also moves. The settling velocity of the sample particles can be calculated from the velocity of the peak movement.

The characteristic of the analytical ultracentrifuge is that it can obtain some important information in a short time with a small amount of samples. It can determine the existence of biological macromolecules, estimate its approximate content, and calculate the sedimentation coefficient of biological macromolecules. According to the interface diffusion, the size of the molecule can be estimated; the heterogeneity of the molecule and the proportion of each component in the mixture can be detected; the molecular weight of the biological macromolecule can be determined; and the conformational change of the biological macromolecule can also be detected.

Our company provides centrifuges with a speed of 4000, 6000, 8000 and 11000 rpm for you to choose from.