Emission and Atomic Absorption Spectrochemical Methods

In these methods of analysis the sample is subjected to temperatures at which its constituent compounds are dissociated into free atoms or converted to temperature-stable molecules. In emission methods, use is made of the fact that a small proportion of the free ground-state atoms or molecules present in a flame, arc or spark are excited to energy levels above the ground-state by heat or electrical effects, then dissipate this energy, either directly or stepwise, by emission of light at wave-lengths characteristic of the atomic or molecular species involved; atomic absorption analysis is based on the fact that free ground-state atoms of an element are capable of absorbing light at the same wave-lengths as the light which they would emit if excited to energy levels above the ground-state.