SPECTRAL ANALYSIS

From Big Medical Encyclopedia

SPECTRAL ANALYSIS (Latin spectrum representation, vision + Greek analysis release, decomposition) — a physical method of qualitative and quantitative test of atomic and molecular composition of substance, studying of its structure and character of intramolecular bonds. Different types

of C. and. are widely used in practice of medicobiological researches, and in particular for definition in various biol. liquids of content of proteins, nucleinic to - t, vitamins and other substances.

Page and. it is based on spectroscopy of atoms and molecules and it is carried out by studying of their ranges (see Spectroscopy). Distinguish S. and. atomic (EXPERT), molecular (MCA), issue and absorbing. Define element structure of a sample by the EXPERT on atomic (ion - to emission spectrums and absorption) MCA allows to determine a moleka, lyarny composition of substance by molecular spectrums of absorption, a luminescence, combinational light scattering. Issue S. and. absorbing S. is based on the analysis of emission spectrums of the atokhm, ions and molecules excited in various ways, and and. — on the analysis of absorption spectrums of electromagnetic radiation objects of a research (atoms, molecules, ions of the substance which is in various aggregate states).

In biology and medicine use issue and absorbing S. more often and. Test of the analyzed material is entered one way or another into a so-called atomizer — the device providing evaporation of firm or liquid tests and dissociation of connections on atoms (ions). In issue S. and. atoms (ions) of test are transferred to excited state, their radiation in the spectral device will be transformed to a range, to-ry and is registered (see. Molecule ). About existence in test of atoms of this or that element judge by emergence in spectrograms of analytical lines of this element. At quantitative the EXPERT is compared intensity of two spectrum lines in a range of test, one of to-rykh belongs to the defined element, and another, called usually by the line of comparison — to a basic element of test, concentration to-rogo shall be known, or to the element of the known concentration («the internal standard») which is specially entered into test. For quantitative assessment build the calibration schedules reflecting dependence of intensity of the analyzed spectrum line on concentration of the studied element in a set of reference tests.

For excitement of radiation in issue S. and. use an arch of direct or alternating electric current, the spark category, a flame and so forth. Important issue S.'s kind in the practical relation and. is flame photometry (see).

Absorbing S. and. it is based on measurement of the absorption by atomic steam of a light flow emitted by a source of discrete radiation (usually by a lamp with the hollow cathode). The devices working by this principle received the name of atomic and absorbing spectrophotometers (see. Spektrofotometriya ).

During the carrying out MCA carry out high-quality and quantitative comparison of a range of the studied sample with ranges of individual substances. In medical - biol. researches the greatest distribution was gained by S. and. molecular spectrums of absorption in infrared (IK), ultra-violet and visible spectral ranges. In some cases MCA combine with other methods of identification of substances, napr, with hromatografichesky (see. Chromatography ).

MCA in an IK-spectral range is connected with studying of the absorption spectrums caused by the main fluctuations of almost all groups meeting in organic compounds. The molecules having identical structural elements (groups) find common features in IR spectrums of absorption, for example the C=0 group corresponds to a strip of 5,49 — 6,17 microns (1820 — 1620 cm-1), SH group — 3,90 — 3,88 microns (2565 — 2575 cm ~ x), CN group — 4,54 — 4,35 microns (2200 — 2300 cm ~) etc. Presence of such characteristic strips at vibration spectrums of various substances allows to establish existence of certain functional groups and in many cases to define structural type of substance. The interpretation of ranges of organic compounds based on characteristic frequencies of groups is considerably empirical and is connected with careful comparison of many ranges as they are strongly influenced by intermolecular interactions and many intramolecular factors.

MCA in visible and UF-spectral ranges as well as IK-spektro-skopiya, can serve for identification of these or those chemical connections. Finds the greatest application of MCA at quantification, identification of structural parameters of macromolecules, and also in the analysis of a course of nek-ry chemical reactions. Light absorption by complex organic compounds is defined by existence in them of certain chemical groups, napr, containing double bonds (olefins, dienes, polyenes) or acetylene bonds (polyenes and enina). Intensively absorb light in visible and UF-spectral ranges carbonyl and aromatic groups. In process of complication of structure of a molecule (increase in chain length, number of conjugated double bonds) the maximum of absorption, as a rule, moves in a long-wave spectral range. The absorption spectrum of chromophores caused first of all by their chemical structure depends also on the size pH, polarity of solvent or properties of nearby molecules. Sometimes for the purposes biol. researches enter the additional chromophore («reporterny» group) differing in the spectral relation from other parts of a molecule into structure of the studied molecule.

MCA — one of the leading methods in practice biol. researches. It is widely used for determination of content in biol. liquids of various ions, measurements of concentration of proteins, nucleinic to - t, vitamins, enzymes etc.

An important kind of MCA in the practical relation is luminescent S. and. (see. Luminescence ). By means of spectral fluorescence analysis, i.e. as a result of determination of parameters fluorescence (see) and phosphorescence (see), it is possible to receive data on concentration and conformation of molecules, their interaction with solvent and so forth. The luminescent method of the analysis thanks to its high sensitivity is used for identification and localization in living cells of such substances, to-rye it is impossible to find by usual methods.

See also Microspectral analysis , Rentgenospektraljny analysis .


Bibliography: Gusinsky M. N. and Lobachev K. I. State and tendencies of development of an atomic and absorbing spektrofotometriya, M., 1975; Karjakin A. V. and Gribovskaya I. F. Issue spectral analysis of objects of the biosphere, M., 1979, bibliogr.; V. J price. Analytical atomnoabsorbtsionny spectroscopy, the lane with English, M., 1976; Raykhbaum Ya. D. Physical bases of a spectral analysis, M., 1980, bibliogr.; Tarasov K. I. Spectral devices, L., 1977; F r and y-felder of. Physical biochemistry, the lane with English, M., 1980.


R. R. Lidemang.

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