The CENTRIFUGE — the device for creation of the centrifugal force used for the purpose of division of heterogeneous mix into components of various density.
The first C., intended for separation of cream from milk, it was designed in 1877 in Germany by W. Lefeld. Soon C. became an integral part of the equipment of scientific laboratories.
Fig. Centrifuge refrigerator (TsR-21): / — cover of the working (rotor) camera; 2 — the operating console; 3 — the case of the centrifuge.
In 1922 Swedish fizikokhimik T. Svedberg designed essentially new type C. — the analytical ultracentrifuge with optical system.
CENTRIFUGE C. are widely applied in laboratory practice (see Centrifuging, At ljtratsentrifugirova-
ny), in air and space medicine as the research and test stand to a training of pilots and astronauts (see Centrifuges in air and space medicine), in the industry, to domestic needs, etc.
Laboratory C. are intended for division biol. liquids on fraction with the diagnostic purpose, e.g., for definition of a volume ratio of components of blood of the patient or for the further analysis of the allocated fraction for the purpose of definition of chemical structure, structure, molecular weight (weight) etc. (e.g., for identification of dins-ma-globulins of blood serum). C. consists of the drive, a rotor, the case, the working (rotor) camera and control systems. The drive can be manual or electric. Purpose of the drive — to report to a rotor rotary motion. The rotor represents the device for placement of vessels with tsentrifugiruyemy substance.
Principle of work of C. is that the centrifugal force arising at rotation of a rotor displaces the particles which are in solution in the direction from an axis of rotation under a condition if particle density exceeds density of solution.
In laboratory practice apply C. general purpose (frequency of rotation of a rotor to 6000 — 8000 about! mines), high-speed refrigerator C. (frequency of rotation of a rotor to 18 000 — 25 000 rpm) and ultracentrifuges (frequency of rotation of a rotor to 75 000 — 80 000 about! mines). The special group is made by highly specialized C., intended, as a rule, for standard a wedge, blood tests, napr, for definition of gematokritny number (see) or departments of an urocheras; cut-off frequency of rotation of a rotor of such C. can reach 15 000 about! min. To group of highly specialized C. carry also devices, with the help to-rykh divide a whole blood into plasma and uniform elements (see the Plasma exchange). The principle of movement of liquids under the influence of centrifugal force is used in centrifugal analyzers (automatic laboratory analyzers of parallel type) allowing to conduct a simultaneous research of several tests biol. liquids.
Range of C. general purpose it is very wide — from manual C. weighing less than 1 kg to heavy floor devices with the built-in refrigerating unit and several replaceable rotors. Nek-rye Ts. are supplied with the high-speed prefix allowing to carry out division with a frequency of rotation up to 20 000 about! min. They are applied as in a wedge, medicine (e.g., to department of an urocheras, receiving a blood plasma), and to medicobiological researches (e.g., in a serology, biochemistry, pharmacology).
High-speed refrigerator C. — difficult floor devices with the powerful electric motor, the refrigerating unit and vacuum installation (fig). They are applied in large a wedge, and biochemical laboratories to the preparative purposes: to a razda
a leniye of fine particles (e.g., lipoproteids, viruses, bacteria), cellular organoids (kernels, mitochondrions, ribosomes), and also high-molecular organic and inorganic polymers at a set-point temperature. In a set of high-speed refrigerator C. about 10 — 15 replaceable rotors enter.
Ultracentrifuges divide on analytical and preparative. They are applied in large research laboratories. By means of analytical ultracentrifuges investigate sedimentation properties of macromolecules for definition of their purity, molecular weight and structure (see Sedimentation). Preparative ultracentrifuges apply to unmixing of proteins, nucleinic to - t, oligo-and the polysaccharides taken in large volumes. The received components use for the subsequent analysis, napr, for definition of structure or biol. activities of the emitted substances.
About 40 replaceable rotors are included in the package of preparative ultracentrifuges.
The ultracentrifuge consists of the following systems: drive, cooling of the engine, oil, vacuum, thermostatings of a rotor. Their normal functioning is ensured by control systems and regulations, functions to-rykh in a number of ultracentrifuges are performed by the microprocessor or the COMPUTER. At the same time reliability of operation of the device considerably increases, and also there is vozkhmozh-ny a program control process of ultracentrifuging with simultaneous calculation of necessary sedimentation constants.
The rotors applied in C., are made of high-strength and corrosion-resistant alloys of titanium or aluminum. Depending on a design rotors happen angular, to suspended glasses, zone, flowing and vertical. Rotors of the same type differ from each other in the marginal frequency of rotation, volume of tsentrifugiruyemy solution, number of cells or glasses, a tilt angle of cells (angular rotors).
Centrifuging of the studied substance is carried out in the special test tubes or vessels which are included in the package of rotors. As material for them serve certain grades of high-strength glass and stainless steel, and also nek-ry types of polymers (e.g., polyethylene, a nitrate cellulose, polycarbonate, etc.).
Operation of laboratory C. does not demand, as a rule, special training of service personnel. From the point of view of the accident prevention vibration of a rotor owing to its uneven loading is undesirable. In order to avoid it before centrifuging of a test tube with drug it is necessary to weigh on centrifugal scales. During the work with replaceable rotors for extension of term of their service it is necessary to be careful at a nasazhivaniye and removal of a rotor from a shaft of the drive, and also to protect them from blows, influence of moisture, acids, alkalis, etc. Non-compliance with these rules can lead to accident.
In a design of high-speed refrigerator C. and ultracentrifuges the means of protection warning a possibility of an exit of the device out of operation are provided. On a case of destruction of a rotor during centrifuging the working (rotor) camera has armored protection.
Protective service behind laboratory C. specialists of technical service according to the special instructions developed for each type C carry out. At dlitel-
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nomas storage of C. subject to preservation, as well as all similar electromechanical devices.
Industrial C. differ from laboratory in the big sizes and more difficult device of rotors. They are applied in himikofarmatsevtichesky, microbiological, chemical, food, mining and other industries.
Bibliography: B about at e N of T. Introduction to ultracentrifuging, lane e English, M., 1973; Methods of practical biochemistry, under the editorship of B. Williams and K. Wilson, lane with English, M. 1978; V. I Falcons. Centrifuging, M., 1976. I. Ya. Vostrikov.