A Quick Look at Atomic Absorption Spectroscopy

Atomic absorption spectroscopy, or AAS, is an analytical procedure for the quantitative and qualitative determination of chemical elements in a given substance. It employs the absorption of light by free atoms in their gaseous state

Atomic absorption spectroscopy, or AAS, is an analytical procedure for the quantitative and qualitative determination of chemical elements in a given substance. It employs the absorption of light by free atoms in their gaseous state. This technique is used in analytical chemistry to determine the concentration of a specific element, which is known as the analyte, in a particular sample. It can be used to determine more than 70 different elements either in solution or in solid samples.

A Quick History

Atomic absorption spectroscopy was first used and its underlying principles established in the latter part of the 19th century by University of Heidelberg professors Gustav Robert Kirchhoff and Robert Wilhelm Bunsen. The modern form of AAS was then developed by a team of Australian chemists led by Sir Alan Walsh during the 1950s.

AAS Instrumentation

To successfully analyze a sample using atomic absorption spectroscopy, it needs to be atomized first. While there are several types of atomizers that can be used for this purpose, the most common atomizers being used these days are flames and electrothermal atomizers. The atoms will then be subjected to optical radiation, wherein the radiation source is either an element-specific line source or a continuum radiation source. The radiation will then pass through a monochromator so that the element-specific radiation is separated from any other type of radiation the source might emit.

Flame Atomizers

This is the oldest and most commonly used type of atomizer in atomic absorption spectroscopy. Liquid and dissolved samples are particularly used with flame atomizers. The sample is aspirated using a pneumatic nebulizer and then transformed into aerosol, which is then introduced into a spray chamber. It is then mixed with the flame gases in the chamber and conditioned in such a way that only the finest droplets should enter the flame. It is this process which is responsible for making sure that only 5% of the sample reaches the flame, while guaranteeing a high freedom from interference.

A burner head on top of the spray chamber is responsible for emitting a flame that’s usually 5-10 cm long and a few mm deep. The radiation beam will pass through this flame, and you may adjust the flame gas flow rates to ensure that the highest concentration of free atoms is produced. You may also adjust the burner height such that the radiation beam passes through the zone with the highest atom cloud density, thus resulting in the highest sensitivity.

Electrothermal Atomizers

Atomic absorption spectroscopy using graphite tube atomizers was pioneered by Boris L’vov in Russia sometime in the late 1950s. It was then further investigated by Hans Massmann in Dortmund, Germany. Although there has been a wide variety of graphite tube designs created and used over the years, the dimensions being used these days are typically 20-25mm in length and 5-6mm in diameter. This technique enables the direct analyses of liquid, dissolved, solid, and gaseous samples. A measured volume or a weighed mass of sample is introduced into the graphite tube and then subjected to a temperature program.

Atomic absorption spectroscopy is extensively used in the mining and exploration industries, as well as in the processing of materials in related fields. If you want to learn more about the minute details of this process or about the instruments used and the benefits it delivers, you can visit websites such as www dot aurorabiomed dot com.

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