When a Nitrogen containing sample is combusted at 1000 ℃, Nitrogen Oxide (NO) is formed:
R-N + O2 –> NO + H2O + CO2
After conditioning of the combusted sample, the amount of Nitrogen is detected by Chemiluminescence detection technique.
The formed NO is led into a reaction chamber. Electronically generated Ozone is added which reacts with the Nitric Oxide which forms Nitrogen Dioxide in an excited state (NO2*). The excited NO2 emits light as it reverts to a lower level energy state. The emitted light is detected by a Photomultiplier Tube (PMT).
The amount of detected emitted light, corresponds with the amount of NO. This in turn represents the amount of Total Nitrogen present in the sample. Surplus of Ozone is converted to oxygen by a catalyst.
The equations for this reaction are:
NO + O3 –> NO2*
NO2* –> NO2 + hv