We need a continuous source of radiation in the AAS instrument. The sample is aspirated through the air into the mixing chamber. A ribbon flame is produced in the AAS instrument. At too high temperatures, atoms can be ionized.įuel and oxidant gases are fed into a mixing chamber which passes through baffles to the burner. The temperature should be controlled very carefully for the conversion of atomic vapor. Heat energy is utilized in atomic absorption spectroscopy to convert metallic elements to atomic dissociated vapor. Any atomic absorption spectroscopy instrumentation has the following types of components,Ītomization can be carried out either by a flame or furnace. Atomic absorption spectroscopy instrumentationįor instrumentation, flame, non-flame, and graphite furnace are available in atomic absorption instruments. Such high temperatures can be attained by using an oxidant in the flame along with fuel gas in atomic absorption spectroscopy.įor example, we used oxyacetylene flame for the analysis of aluminum, titanium, and rare earth elements in an AAS instrument. Therefore, we need a high temperature for the vaporization of such metals. Some metals are not easily atomized or vaporized. These metals are easily vaporized at low temperatures. We used low temperatures for metals like copper (Cu), lead (Pb), zinc (Zn), and cadmium (Cd). Usually, natural gas, propane, butane, hydrogen, and acetylene are used as fuels to create a flame.Īir, oxygen, nitrous oxide, and a mixture of nitrous oxide and acetylene are used as an oxidant for flame creation in atomic absorption spectroscopy.Ī list of various flames with maximum temperate is given below the table, Atomic absorption spectroscopy flame We used fuel and oxidant to create an atomic absorption spectroscopy flame. Usually, lines arising from the ground state are almost important in atomic absorption spectroscopy. From the ground state of an atom is excited to a higher energy level by absorption of energy.Ītomic spectra are identified by sharp lines which can be distinguished from broadband spectra associated with molecules. The electronic transition is specific to a particular element. Light at this wavelength has absorbed energy to excite another electronic state. Elements with low excitation energy can be determined by flame emission while high excitation energy can be determined by atomic absorption spectroscopy.Ītoms absorb light at a definite wavelength depending on the nature of chemical elements. Many difficult and time-consuming instruments were replaced after the discovery of AAS.Ītomization, hollow cathode lamp, monochromator, detector, and recorder are the main components in atomic absorption spectroscopy instrumentation. A low pressure of argon in the lamp insures that the line width from the hollow cathode lamp is less than the line width of the absorbing species.In 1955 Alan Walsh from Australia applied the principle and instrumentation of atomic absorption spectroscopy for the analysis of chemical elements. Collisions of excited state sputtered atoms with argon atoms will lead to broadening of the output of the hollow cathode lamp and potentially lead to the same problem described above with the use of a continuum source. The pressure of the argon is low to minimize collisions of argon atoms with sputtered atoms. With this understanding we can ask why the hollow cathode lamp has a low pressure of argon filler gas. Therefore, hollow cathode lamps, which emit intense narrow lines of radiation specific to the element being analyzed, are needed for atomic absorption measurements. Reducing the slit width on a continuum source to a level that would provide a narrow enough line to respond to atomic absorption would reduce the power so that it would not be much above the noise. The problem with reducing the slit width is that it reduces the number of photons or source power reaching the sample. What is the problem with reducing the slit width of the monochromator to get a narrower line? Atomic absorption line superimposed onto the overall output of a continuum source/monochromator system.
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