Determination of SO2:
As you know, sulphur dioxide is one of the major components of air pollution in several parts of the world. The combustion of sulphur holding fossil fuel for domestic use and power generation along with not so well controlled combustion of the fossil fuels in industrial installations is globally the chief contributors to the raised environmental levels of SO2. This increased concentration has serious effect on the human health as well as the ecological system. Thus, monitoring and control of the SO2 concentration in the environment is of paramount significance. It is pertinent, thus, to have reliable methods for the determination of SO2 in the environmental samples.
There are various good methods for monitoring of SO2 in the air samples. In the general employed West Geake method, the air is bubbled by 0.1 M sodium tetrachloromercurate solution to acquired stable, non-volatile dichlorosulphitomercurate
[HgCl4]2- + 2SO2 → [Hg(SO3)2]2- + 4Cl- + 4H+
The complex is made to react along with pararosaniline and formaldehyde to form the intensely colored para-rosanilinemethylsulphonic acid. An absorbance of the solution is measured through means of a appropriate spectrophotometer. Concentration of sulphur dioxide within the range of 25 - 1050 µg /m3 could be measured under these conditions.
Within the fluorimetric method, a pulsed UV source is employed to excite the SO2 molecules. Those excited molecules emit features fluorescence along with intensity proportional to the concentration of SO2.
SO2 + hν → SO*
SO* 2→ SO 2 + hν (fluorescen ce)