The drying zone is a bright zone with small width and low brightness near the burner gap. Most of the test solution is dried into solid particles here.
The evaporation zone is also called the first reaction zone. There is usually a clear blue band. The temperature in this area is not high because of insufficient combustion. Dry solid particles melt and evaporate here.
The atomization zone is a small thin layer near the evaporation zone, which burns completely and has the highest flame temperature. It is an area with high atomic density of gas, so it is an important spectral observation area for flame atomic spectral analysis.
The ionization zone is also called the second reaction zone. Due to the full combustion of fuel gas in this area, the temperature is very high, and then outward, due to the cooling effect, the flame temperature drops sharply, leading to the ionization of some atoms, some of which were originally formed by strong high temperature combination. The spatial distribution of free atoms in flame is related to flame type, combustion state and element properties. The following figure shows the distribution curves of absorption values of three elements along the flame height. The maximum absorption value of magnesium is about in the middle of the flame. The initial absorption value increases with the increase of flame height, which is due to a large number of magnesium atoms produced by staying in the hot flame for a long time. However, when approaching the second reaction zone, magnesium oxide obviously begins to form. Because it does not absorb radiation of the selected wavelength, the absorption value of magnesium drops rapidly.
neutral flame
The ratio of fuel gas to auxiliary fuel gas of the flame is close to the stoichiometric relationship of chemical reaction between them. It has the characteristics of high temperature, low interference and low background, and is suitable for the determination of various elements.
A rich flame
Rich flame, that is, the ratio of fuel gas to auxiliary fuel gas is greater than stoichiometry. This kind of flame burns incompletely, the temperature is low and the flame is yellow. Rich flame is not as stable as neutral flame because of its high background and many interferences. However, due to its strong reducibility, it is suitable for the determination of elements that are easy to form refractory oxides, such as iron, diamond and nickel.
Thin flame
The ratio of the fuel gas to the auxiliary fuel gas is less than the stoichiometric ratio. This flame has strong oxidation and low temperature, which is beneficial to the determination of elements that are easy to dissociate and ionize. Such as alkali metals and the like.