The radiant energy absorbed by the electrons is directly related to the transition that occurs during this process. When the atom is exposed to its own unique wavelength, it can absorb the energy (photons) and electrons move from a ground state to excited states. The electrons within an atom exist at various energy levels. The amount of light absorbed at this wavelength is directly proportional to the concentration of the absorbing ions or atoms. When a sample containing copper (Cu) and nickel (Ni), for example, is exposed to light at the characteristic wavelength of Cu, then only the Cu atoms or ions will absorb this light. Firstly, all atoms or ions can absorb light at specific, unique wavelengths. The basic principles of AAS can be expressed as follows. Today, most analytical laboratories will boast at least one atomic absorption spectrophotometer. It took him several more years to convince manufacturers to use atomic absorption spectroscopy (AAS) for the detection of metals, but he eventually succeeded. By teatime on Monday morning, he showed that it could be done. Walsh decided to measure absorption, not emission. The normal procedure in spectroscopy was to vaporize an element and measure the emission spectra, but this technique was flawed and produced inaccurate results. They were able to reproduce the black lines observed in the solar spectrum in the laboratory, thus allowing the identification of absorbing atoms in the corona through their emission spectra.Īlan Walsh, 2 a Lancashire-born physicist was working in his garden on a Sunday morning somewhere in the early 1950s when an idea that would solve a huge analytical chemistry puzzle popped up in his mind: how to accurately measure small concentrations of metallic elements by spectroscopy. Bunsen and Kirchoff demonstrated soon after that each chemical element had a characteristic color or spectrum when heated to incandescence (e.g., sodium (Na) yellow potassium (K) violet). In 1832, Brewster concluded that atomic vapors in the atmosphere absorbed some of the radiation from the Sun resulting in the detection of these lines. The English chemist, Wollaston, was the first to observe dark lines in the solar spectrum that became known as Fraunhofer lines. What are the applications of atomic absorption spectroscopy? Strengths and limitations of atomic absorption spectroscopy Interpreting an atomic absorption spectrometric output Radiation sources in AAS and signal detection Atomizing techniques - graphite furnace atomic absorption spectroscopy (GFAAS) - Atomizing techniques – specialized techniques Atomizing techniques - flame atomic absorption spectroscopy (FAAS) 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.What is the principle of atomic absorption spectroscopy? 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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