Depending on the sample matrix and nitrogen concentration, different method approaches are available. For the determination of nitrogen as a main component, the sample is combusted in oxygen. After reduction of the resulting nitrogen oxides and binding of interfering reaction gases, the nitrogen content is determined gas volumetrically or by thermal conductivity detection.
For nitrogen trace analyses either methods by chemiluminescence or carrier gas hot extraction are used, depending on the matrix.
The detection by chemiluminescence measuring cell is done after combustion of the sample and ozonization of the released nitrogen oxides.
The carrier gas hot extraction is especially applicable for metals, alloys or ceramic materials. It allows a melting of the sample with melt-forming additives at up to 2700°C. The nitrogen concentration is determined by thermal conductivity measuring cell.
Nitrogen determinations according to Kjeldahl are also possible. With this method, nitrogen is determined titrimetrically after sulfuric acid digestion and conversion of the resulting ammonium sulfate into the form of ammonia.