Why is the AES a reference method for alkali metals?
In which areas is flame photometry used?
Learn more about flame photometry!
Atomic emission spectroscopy (AES) is a method of chemical analysis that uses the intensity of light emitted from a flame at a particular wavelength to determine the quantity of Ca, Na, K, Li, Ba in a aqueous sample. The sample is brought into the flame as a sprayed solution. The heat from the flame evaporates the solvent and breaks the chemical bonds to create free atoms. The thermal energy transfers the atoms in excited electronic states so that they emit light when they return to the electronic ground state. Each element emits light at a characteristic wavelength. The wavelength of the atomic spectral line gives the identity of the element while the intensity of the emitted light is proportional to the number of atoms of the element.
Reference method for alkali metals. Why?
The F-AES flame reaches a temperature of 1900°C which provides enough energy to promote atoms of alkali elements like Ca, Na, K, Li, Ba from their ground state to an excited energy level without the risk of ionisation. Once the electrons fall back from these high energy level to their ground energy state, light will be emitted with a characteristic wavelength.
Since no atoms get ionized all atoms in the sample will be captured defining the real concentration value.