Atomic Emission Spectrometry Based on Plasma Sources:

Plasma is a high energy source which is an electrically neutral conducting gaseous mixture having a significant concentration of cations and electrons. As an electrical conductor it can be heated inductively by coupling with an oscillating magnetic field. The temperature of the plasma may be of the order of 5,000 to 8,000 K. You would learn about plasma sources. The plasma based AES in principle, is similar to the flame photometry; the only difference being that flame is replaced by much more energetic atomization-excitation processes using plasma. In emission work, the argon plasma is frequently employed.

The analyte sample is introduced into the centre of the plasma as an aerosol with the help of a nebuliser using argon flow. Since in a flame, in plasma also a sample undergoes several transformations such as desolvation, vaporisation, atomisation, ionisation and excitation. An excitation and ionisation occurs because of collisions of the analytical atoms with high energy electrons. The high temperature assures that most samples are completely atomised, therefore, some molecular species e.g., N₂, N₂⁺, OH, C₂, etc. do exist in the plasma and are measurable. As the energy of the plasma source is quite high it ensures the excitation of the atoms of all the elements present in the sample which then relax by emitting EM radiation of characteristic wavelengths of different elements. Therefore, it is a multielement technique.