Atomic-absorption analysis of the substance
ATOMIC-ABSORPTION ANALYSIS OF THE SUBSTANCE (EN: atomic-absorption material analysis; DE: atomare Absorptionsanalyse der Stoffe; FR: analyse de la matiere par absorption atomique; ES: análisis del material del por absorcion atomica; RU: атомно-абсорбционный анализ вещества) is the method of the quantitative determination of the elemental composition of the substance, which is being researched, according to the atomic absorption spectra, which is based on the ability of the atoms to selectively absorb the electromagnetic radiation within the various ranges of the spectrum. They conduct the atomic-absorption analysis on the special devices, namely, the absorption spectrophotometers. They dissolve the sample of the material, which is being analyzed (usually with the formation of the salts); they feed the solution in the form of the aerosol into the flame of the burner. Under the impact of the flame (3000 degrees Celsius), the molecules of the salts dissociate into the atoms, which can absorb light. Then they pass through the flame of the burner the beam of light, within the spectrum of which there exist the spectral lines, which are corresponding to one or another element. They isolate the researched spectral lines from the total radiation with the help of the monochromator, and record their intensity with the help of the block of registration. The mathematical processing is conducted according to the formula:
J = J0e^-kvI, where J and J0, - the intensities of the passed and incident light; kv, - the coefficient of absorption, which depends on the frequency of the light; I, - the thickness of the absorbent layer.
Knowing kv and I, it is possible to determine the optical density of the vapours of the material, and with its help, according to the calibration graphs, the concentration of the material. They conduct the atomization most often within the flame of the air - acetylene or nitrous oxide - acetylene.
The atomic-absorption analysis is characterized by the great selectivity, small limits of the detection (10^-1 and 10^-4 micrograms per millilitre for the flame and flameless variants respectively), good reproducibility (the relative standard deviation is 0.005-0.02), rapidity (up to 300 measurements per hour), and high degree of automation.
They use the atomic-absorption analysis for the determination of both the trace (10^-6%) and macro-scale quantities of approximately 70 elements within the various rocks, ores, and minerals, within the products of the petrochemistry and metallurgy, within the biological objects, and so on. During the geochemical prospecting under the conditions of the field laboratories, they use the flameless method for the determination of the micro-impurities (from 10^-7% to 10^-1%) of mercury.
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