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What is Atomic Absorption Spectroscopy?

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  • Written By: Heather Scoville
  • Edited By: Susan Barwick
  • Last Modified Date: 17 November 2016
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Atomic absorption spectroscopy is a technique used to identify which minerals or metals are present in a liquid or a solid. A light source is directed at the sample and the absorption of that light is measured and compared to known absorption spectra of various metals. Every element has a unique spectrum that appears when it is heated or absorbs light.

The amount of the metal or mineral in the sample does not matter when using atomic absorption spectroscopy. Even trace amounts can be identified using this method. The more of the metal present in the sample, the larger the absorption that will be detected. The most common metals identified by this method are iron, aluminum, copper, and lead, but any element can be identified.

In flame atomic absorption spectroscopy, the machine consists of several parts. The desired wavelength of light originates from a hollow cathode lamp that shines directly onto the sample. A nebulizer takes the liquid sample and creates a mist which is blown into a flame. The heat of the flame liberates individual elements which then absorb the light. Next, a monochromator filters out the unwanted spectral lines and a photomultiplier determines the amount of absorption occurring.

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Using different hollow cathode lamps with various wavelengths of light, atomic absorption spectroscopy can identify several elements at the same time. In this case, they would be isolated in the monochromator, and the photomultiplier would show the amount of absorption for each wavelength.

Furnace atomic absorption spectroscopy is similar to flame atomic absorption spectroscopy. Instead of the sample being sprayed into an open flame, a drop of the sample is heated within a graphite furnace. The furnace is heated by an electrical current and it is insulated by a gas, usually argon.

When performing atomic absorption spectroscopy, one should ensure that the hollow cathode lamp's beam is lined up directly with the sample. If the beam is not aimed at the sample, the absorption numbers will not be accurate, and components of the sample may not be detected. Calibration of the machine before using the actual sample can avoid this problem.

There are several applications of atomic absorption spectroscopy. It is often used to determine the minerals and metals, such as the mercury, are present in water samples. It can also be used to detect the presence of lead in everyday products, such as paint.

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