About Atomic Absorption Spectroscopy

Atomic absorption spectroscopy is the process of determining the chemical elements in a given substance, qualitatively and quantitatively. The technique employs the absorption of light by free atoms in their gaseous state.

Atomic absorption spectroscopy is the process of determining the chemical elements in a given substance, qualitatively and quantitatively. The technique employs the absorption of light by free atoms in their gaseous state. In analytical chemistry, this procedure is used to find out the concentration of a particular element, known as the analyte, in a sample. More than 70 different elements in solution or solid samples can be determined by this method.

A Brief History

This method was first employed and the underlying principles made known towards the end of the 19th century by the University of Heidelberg professors Gustav Robert Kirchhoff and Robert Wilhelm Bunsen. AAS was given a modern form by a team of Australian chemists led by Sir Alan Walsh during the 1950s.\

Instrumentation of AAS

In order to analyse a sample with atomic absorption spectroscopy, it has to be first atomized. Though there are several kinds of atomizers that can be used for this purpose, the most commonly used ones are flames and electrothermal atomizers. After this, the atoms are made subject to optical radiation, with the radiation source being either an element-specific line source or a continuum radiation source. The radiation is further passed through a monochromator such that the radiation that is specific to the particular element is separated from all other types of radiation that the source might emit.

Flame Atomizers

The oldest and most commonly used kind of atomizers in AAS is flame atomizers. Both liquid as well as dissolved samples can be analyzed with flame atomizers. The sample under observation is first aspirated with a pneumatic nebulizer. After that, it is altered into aerosol, which is then set up into a spray chamber. The flame gases in the chamber are mixed with this and conditioning is done such that only the finest droplets enter the flame. This process is in fact responsible for ensuring that not more than 5% of the sample reaches the flame along with assuring freedom from interference.

The burner head, which is placed on the top of the spray, chamber guarantees that flame which is normally 5-10 cm long and a few mm deep is emitted. The radiation beam is allowed to pass through this flame and you can also adjust the flame gas flow rates to make certain that the highest concentration of free atoms is formed. The burner height can also be adjusted such that the radiation beam passes through the zone with the maximum atom cloud density, thus resulting in the maximum sensitivity.

Electrothermal Atomizers

AAS using graphite tube atomizers was initiated by Boris L’vov in Russia in the latter half of the 1950s. Further it was investigated by Hans Massmann in Dortmund, Germany. Though there has been so many types of graphite tube designs used over the years, the standard dimensions now are 20-25mm in length and 5-6mm in diameter. This procedure allows the direct analysis of liquid, dissolved, solid and gaseous samples. After a measured volume of the sample is put into the graphite tube, it is subjected to a temperature.

Atomic absorption spectroscopy is broadly used in the mining and exploration sectors. This technique is also employed in the processing of materials in some fields. For all those would like to have more insight into the minute details of AAS and its benefits, websites like www.aurorabiomed.com are going to be very useful.

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