ACTIVATION ANALYSIS

From Big Medical Encyclopedia

ACTIVATION ANALYSIS — a method of definition of concentration of stable isotopes in biological samples by measurement of radiations of kernels of these isotopes activated by various particles and γ-quanta..........

And. and. for the first time made Hevesha and Levi (G. Hevesy, H. Levi) in 1936. Radiation of samples for the purpose of activation of stable isotopes can be made neutrons (n), protons (p), deuterons (d), α-particles, n-mesons and rigid γ-radiation.......... Determination of content of active isotopes is made or by radiochemical analysis with the subsequent measurement of activity of isotopes (see. Radiometry ), or by measurement of radiation of active isotopes in the whole samples by means of spectrometers of radiations.

For quantitative definition of stable isotopes in a biological sample it is necessary to know the nuclear reactions (see) leading to formation of the corresponding radioisotopes, conditions of radiation — particle fluxes and γ-quanta, a radiation time and time from the end of radiation prior to measurements. For identification of radioisotopes it is necessary to know half-lives and schemes of disintegration (percentage of radiation and energy of the let-out particles or quanta). The quantity of the formed radioisotope is proportional to quantity of the corresponding stable isotope and total quantity of the particles of a pla of γ-kvant absorbed in a sample and depends on half-life and a radiation time since in the course of radiation there is a disintegration of isotopes.

Sensitivity and accuracy And. and. strongly fluctuate. Accuracy of determination of absolute content of elements in a sample does not exceed 20 — 50% therefore, as a rule, the maintenance of elements in a sample is determined by relative methods. In a crust, time the greatest application was found by neutron activation (neutron aktpvatsionny the analysis).

And. and. finds more and more broad application in medicine and biology for determination of content of stable isotopes, in particular microelements in various fabrics and bodies (tissues of an eye, bone tissue, malignant tumors, etc.) and biosubstrates (allocations, blood, etc.). For studying of functions of bodies and a metabolism it is normal also of pathology, for the analysis of dynamics and mechanisms of sorption and penetration through skin and overalls of a number of toxic connections A. and. apply in combination with method of radiotracers and with introduction of stable isotopes (iodine, uranium, etc.). And. and. it is used for studying of exchange and concentration of stable isotopes and connections in a live organism in its allocations, and also for the analysis of external environment and the connections coming to an organism.

Bibliography: R. A. smiths. Activation analysis, M., 1967, bibliogr.; Taylor D. Neutron emission and the activation analysis, the lane with English, M., 1965, bibliogr.

Yu. M. Shtukkenberg.

Яндекс.Метрика