Principle of Atomic Emission Spectrometry:

In atomic emission spectrometry (AES) a reproducible and representative amount of the sample is introduced within an atomization-excitation source whereas it is converted within atomic vapours of the analyte in excited state. The analyte solution, when introduced within the flame, undergoes a number of procedures to be atomised and then get excited. Since the excited state is short lived and an excited atoms return back to the ground state after an extremely short lifetime (typically 10^{- 6} to 10^{- 9} s). This is accompanied by the emission of electromagnetic radiation, generally within the form of light in the UV-VIS region. This radiation is characteristic of the constituents of the sample. Because resolution of the emitted radiation produces an emission spectrum, whose detailed analysis could be exploited to acquires qualitative as well as quantitative details of the analyte. The versatility of AES is due to the availability of a wide range of atomisation-excitation sources. These extend from dc arc, ac spark and universal arc-spark, to dc plasmas, microwave plasmas, glow discharge lamps, lasers and inductively coupled plasma (ICP). Accordingly, there are many ways in which AES can be carried out, and each of these ways has many variations.

You would recall that it is an easy, rapid and inexpensive method for routine analysis of alkali and alkaline earth metals such as, potassium, sodium, lithium, calcium and barium in environmental, biological and clinical samples especially in biological fluids and tissues. You know which in flame photometry natural gas and air flame is employed for atomisation and excitation of the analyte. As the temperature of the flame is not high enough to excite transition elements and non metals; the technique is quite restrictive. It could be professionally employed for the detection of alkali and alkaline earth metals only.