Fate of the Sample in the Flame:
In a classic flame photometric experiment, a solution holding the relevant substance to be analysed is aspirated within the burner and dispersed inside the flame as a fine spray. This procedure is known as nebulisation. Within the flame, the solvent evaporates first, leaving finely separated solid particles that move to hottest region of the flame whereas gaseous atoms and ions are generated. The atoms are excited through absorbing energy available from the flame. Since the excited atoms return to a ground state of lower energy, radiation of wavelength, features of the element, is emitted. The intensity of the emitted radiation is then measured, that could be associated to the concentration of the element present, and that forms the primary of quantitative analysis. The following processes occur in the flame.
i) Desolvation: The sample holding metal particles is dehydrated through the heat of the flame and the solvent is evaporated.
ii) Vapourisation: a heat of the flame vapourises the sample constituents. No chemical modification takes place at this stage.
iii) Atomisation: At this stage the metal ions which were in the solvent are reduced to metal atoms. For instance, Mg 2+ (aq) + 2e → Mg (g). Through heat of the flame and action of the reducing gas (fuel), molecules and ions of the sample species are decomposed and decreased to provide atoms.
iv) Excitation: The atoms at this stage are able to absorb energy from the heat of the flame. An amount of energy absorbed depends on the electrostatic forces of attraction among the negatively charged electrons and the positively charged nucleus. That in turn depends upon the number of protons in the nucleus. As electrons absorb energy that move to higher energy stages and are in the excited state.