Atomic Absorption Spectroscopy AAS

Atomic Level 

Atomic Absorption Spectroscopy  AAS : 

Principle: The sample is vaporized by aspiration of solution into a flame or evaporation from 

electrically heated surface (temperature range: 1800 – 31000

 K). At this condition where the 

individual atoms co-exist, a beam of light is passed through them. The atoms will absorb in 

the visible and ultraviolet region resulting in changes in electronic structure (excited state). 

So, the resultant light beam coming out of the sample will be missing the light in the 

corresponding wave length, which is a measure of the characteristics of the sample. 

Instrumentation :  Sources emitting radiation characteristic of element of interest (hollow - 

cathode lamp), flame or electrically heated furnace, monochromator, detector 

(photomultiplier) and  recorder. The following is the simplified outline of the 

instrumentation: 

Applications : This is the most widely used technique for the quantitative determination of 

metals at trace levels (0.1 to 100ppm), which present in various materials. It utilizes Beer  - 

Lambert Law  for the analysis and a standard curve is obtained by plotting absorbance  vs 

concentration of the samples taken. The usual procedure is to prepare a series of standard 

solutions over a concentration  range suitable for the sample to be analysed. Then, the 

standards and the samples are separately aspirated into the flame, and the absorbances are 

read from the instrument. The plot will give the useful linear range and the concentrations of 

the samples can be found out from the plot. 

Disadvantages : Sample must be in solution or at least volatile. Individual source lamp and 

filters needed for each element, since, each metal has its own characteristic absorption.