Classification and Structure of Centrifuges

Classification and Structure of Centrifuges

(1) Classification of Centrifuges: Internationally, there are three main methods for classifying centrifuges—by application, by rotational speed, and by structure.

By purpose, they can be classified into preparative, analytical, and preparative-analytical dual-purpose types.
 
Centrifuges can be classified according to their rotational speed into low-speed, high-speed, and ultra-high-speed centrifuges, among others.

By structure, they can be classified into benchtop models, multi-tube microvolume models, cell smear models, blood-washing models, high-speed refrigerated models, large-capacity low-speed refrigerated models, and benchtop low-speed automatic balancing centrifuges, among others.

(2) Low-speed centrifuge: It is primarily used for the separation of plasma and serum, as well as for the separation of formed elements from cerebrospinal fluid, pleural and abdominal effusions, urine, and other similar samples.

High-speed centrifuge: It is primarily used in clinical laboratories for the separation of DNA and RNA in molecular biology, as well as in basic laboratories for the separation, concentration, and purification of various biological cells, solutions of inorganic substances, suspensions, and colloidal solutions.

Ultracentrifuge: Ultracentrifuges are classified according to their applications into three types: preparative, analytical, and analytico-preparative.

Preparative ultracentrifuges are primarily used for the separation and purification of biological macromolecules, organelles, viruses, and other similar substances. They enable the graded separation of subcellular organelles and can also be employed to determine the molecular weights of proteins and nucleic acids.

The analytical ultracentrifuge is equipped with an optical system that enables photo-taking, measurement, digital output, and automatic display of results. Through this optical system, the sedimentation process and purity of the test sample can be observed.

(3) Dedicated centrifuge

① Immunohematology centrifuge: Used for clinical blood transfusion, blood typing, crossmatching, lymphocyte separation, platelet separation, and the antiglobulin test, among other applications.

② Microcapillary centrifuge: Used for hematocrit tests, microhematocrit measurements, and the determination of isotopically labeled trace amounts.

③ Urine sediment separation centrifuge: Used for separating formed elements from urine and is compatible with urine analysis workstations.

④ Cell smear centrifuge: Used for the separation and preparation of smears from exfoliated cells in cerebrospinal fluid, pleural fluid, and ascitic fluid.

(4) Structure of low-speed centrifuges, high-speed (refrigerated) centrifuges, and ultrahigh-speed (refrigerated) centrifuges:

① The structure of a low-speed centrifuge consists of several key components, including an electric motor, a centrifugal rotor (rotor head), a speed regulator, a timer, a centrifuge tube, and a base.

② The structure of a high-speed (cryogenic) centrifuge consists of a rotating mechanism, a speed control system, a temperature control system, a vacuum system, a centrifugal chamber, a rotor, and safety protection devices, among other components.

③ The ultracentrifuge (for freezing) mainly consists of four components: the drive and speed control system, the temperature control system, the vacuum system, and the rotor.

(5) Classification, Applications, and Functions of Centrifugal Rotors:

Centrifuge rotors are generally classified into five major categories:

① Fixed-angle swivel head

② Swing-out rotor

③ Continuous-flow rotor

④ Swing-out rotor

⑤ Vertical rotor.

(6) Main technical parameters and performance indicators of the centrifuge:

The main parameters include: maximum rotational speed; maximum centrifugal force; maximum capacity; power supply wattage; temperature control range; operating voltage; speed adjustment range.

Common markings and parameters of centrifuge rotors.

The common markings on centrifuge rotors consist of three parts: the first part is an alphabetic symbol; the second part is a number; and the third part indicates that the rotor is made of different metals. Rotor parameters include Rmax, Rmin, RCFmax, RCFmin, RPMmax, and K, among others.