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When the aerosol droplets enter the flame, the solvent (water, in this case) is evaporated. We

say that the sample is “desolvated”.

The sample is now in the form of tiny solid particles. The heat of the flame can melt (liquefy)
the particles and then vaporize the particles.

Finally the heat from the flame (and the combustion chemistry in the flame) must break the
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bonds between the analyte metal and its anion, and produce free M atoms. This entire
process must occur very rapidly, before the analyte is carried out of the observation zone of

the flame.
After free atoms are formed, several things can happen. The free atoms can absorb the

incident radiation; this is the process we want.
The free atoms can be rapidly oxidized in the hostile chemical environment of the hot flame,

making them unable to absorb the resonance lines from the lamp. They can be excited
(thermally or by collision) or ionized, making them unable to absorb the resonance lines from

the lamp. The analyst must control the flame conditions, flow rates, and chemistry to

maximize production of free atoms and minimize oxide formation, ionization, and other
unwanted reactions.

Flames have been used as cells since the development of AAS. They are still more

popular than other cells. The sample solution is aspirated into the flame small drops. The solvent

in the solution rapidly evaporates because of the heat from the flame. The solid particles of
solute that remain after solvent evaporation melt to form a liquid, evaporate to yield a gas, and

dissociate into atoms. Radiation from the lamp passes through the flame and is partially absorbed
b the sample atoms. The amount of absorption is monitored with the detector.

Prior to its aspiration into the flame, the sample solution is sucked through a small
diameter tube into the stream of oxidant flowing to the flame. The flow of the oxidant past the

orifice to the sample tube provides the partial vacuum required to suck the solution into the

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