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Atomic absorption spectroscopy
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Atomic absorption spectroscopy
Atomic absorption spectroscopy (AAS) is an analytical method for determining the concentration of chemical elements in a sample. The technique is based on the absorption of light by free atoms in the gaseous state. The amount of absorbed light is proportional to the number of atoms of the element present, and this relationship is used to determine the concentration. An alternative technique is atomic emission spectroscopy (AES).
AAS can be used to determine over 70 different elements in solution, or directly in solid samples via electrothermal vaporization, and is used in pharmacology, biophysics, archaeology and toxicology research.
Atomic emission spectroscopy (AES) was first used as an analytical technique, and the underlying principles were established in the second half of the 19th century by Robert Wilhelm Bunsen and Gustav Robert Kirchhoff, both professors at the University of Heidelberg, Germany.
The modern form of AAS was largely developed during the 1950s by a team of Australian chemists. They were led by Sir Alan Walsh at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Division of Chemical Physics, in Melbourne, Australia.
In order to analyze a sample for its atomic constituents, it has to be atomized. The atomizers most commonly used nowadays are flames and electrothermal (graphite tube) atomizers. The atoms should then be irradiated by optical radiation, and the radiation source could be an element-specific line radiation source or a continuum radiation source. The radiation then passes through a monochromator in order to separate the element-specific radiation from any other radiation emitted by the radiation source, which is finally measured by a detector.
Most commonly used are spectroscopic flames and electrothermal atomizers. Other atomizers, such as glow-discharge atomization, hydride atomization, or cold-vapor atomization, might be used for special purposes.
The oldest and most commonly used atomizers in AAS are flames, principally the air-acetylene (C2H2) flame with a temperature of about 2300 °C, and the nitrous oxide (N2O)-acetylene flame with a temperature of about 2700 °C. The latter flame offers a more reducing environment, ideally suited for analytes with a high affinity to oxygen.
Liquid or dissolved samples are typically used with flame atomizers. The sample solution is aspirated by a pneumatic analytical nebulizer, transformed into an aerosol, which is introduced into a spray chamber, where it is mixed with the flame gases and conditioned so that only the finest droplets (< 10 μm) enter the flame. This conditioning reduces interference, but causes only about 5% of the solution to reach the flame.
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Atomic absorption spectroscopy
Atomic absorption spectroscopy (AAS) is an analytical method for determining the concentration of chemical elements in a sample. The technique is based on the absorption of light by free atoms in the gaseous state. The amount of absorbed light is proportional to the number of atoms of the element present, and this relationship is used to determine the concentration. An alternative technique is atomic emission spectroscopy (AES).
AAS can be used to determine over 70 different elements in solution, or directly in solid samples via electrothermal vaporization, and is used in pharmacology, biophysics, archaeology and toxicology research.
Atomic emission spectroscopy (AES) was first used as an analytical technique, and the underlying principles were established in the second half of the 19th century by Robert Wilhelm Bunsen and Gustav Robert Kirchhoff, both professors at the University of Heidelberg, Germany.
The modern form of AAS was largely developed during the 1950s by a team of Australian chemists. They were led by Sir Alan Walsh at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Division of Chemical Physics, in Melbourne, Australia.
In order to analyze a sample for its atomic constituents, it has to be atomized. The atomizers most commonly used nowadays are flames and electrothermal (graphite tube) atomizers. The atoms should then be irradiated by optical radiation, and the radiation source could be an element-specific line radiation source or a continuum radiation source. The radiation then passes through a monochromator in order to separate the element-specific radiation from any other radiation emitted by the radiation source, which is finally measured by a detector.
Most commonly used are spectroscopic flames and electrothermal atomizers. Other atomizers, such as glow-discharge atomization, hydride atomization, or cold-vapor atomization, might be used for special purposes.
The oldest and most commonly used atomizers in AAS are flames, principally the air-acetylene (C2H2) flame with a temperature of about 2300 °C, and the nitrous oxide (N2O)-acetylene flame with a temperature of about 2700 °C. The latter flame offers a more reducing environment, ideally suited for analytes with a high affinity to oxygen.
Liquid or dissolved samples are typically used with flame atomizers. The sample solution is aspirated by a pneumatic analytical nebulizer, transformed into an aerosol, which is introduced into a spray chamber, where it is mixed with the flame gases and conditioned so that only the finest droplets (< 10 μm) enter the flame. This conditioning reduces interference, but causes only about 5% of the solution to reach the flame.
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