Atomic absorption spectroscopy (AAS) is a technique used to analyze elements by measuring electromagnetic radiation (EMR) absorbed by atoms, which causes them to transition to a higher-energy orbit. The most crucial step in AAS is atomization, where the analyte is converted into gas-phase atoms, typically through a flame or furnace. Some of these atoms become thermally excited in the flame, while most remain in the ground state.
When irradiated by EMR of a particular wavelength, these ground-state gas-phase atoms absorb the radiation only if it provides the energy required for their electronic excitation. The difference between incident and transmitted radiant power of EMR is the measure of absorbed radiation, which quantifies the analyte.
Atomic absorption lines are highly narrow, as they generate from characteristic electronic transitions unaccompanied by rotational and vibrational transitions. AAS follows the Beer-Lambert law, which states that the amount of light absorbed is directly proportional to the concentration of the absorbing atoms, assuming a constant path length. AAS is a selective and sensitive technique with detection limits in the nanogram range per milliliter. It is widely used for trace metal analysis in clinical, pharmaceutical, food, mining, environmental, and agricultural fields.
AAS's limitations include the need for solution-phase or volatile solid samples for analysis. In addition, the radiation sources for AAS should either be high-resolution continuum sources or separate line sources for every elemental analysis.
Atomic absorption spectroscopy, or AAS, is an elemental analysis technique based on the principle of absorption of electromagnetic radiation resulting in electronic excitation.
In AAS, the sample is first atomized—converting analytes into gas-phase atoms. Although the flame temperature excites some gas-phase atoms, most remain unexcited.
When electromagnetic radiation of a particular wavelength irradiates an atom, it is absorbed if it provides the exact energy for an electronic transition to a higher-energy orbital.
The difference in the incident and transmitted radiation intensities measures the radiation absorbed, quantifying the analyte.
AAS follows the Beer–Lambert law, where the absorbance directly depends on the concentration of the gas-phase atoms in the flame, assuming a constant pathlength in the flame.
Notably, AAS offers high sensitivity with detection limits in nanogram per milliliter levels and is widely used for trace-metal analysis.
However, AAS necessitates liquid-phase or otherwise volatile solids. Additionally, it requires either a high-resolution continuum-source spectrometer or characteristic radiation sources for every element to be analyzed.
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