Principle of Analysis by Combustion
The combustion of the sample generates uniform compound gasses of the elements C, H, N and S. These combustion products (e.g. CO2, H2O, NO2, etc.) are measured using gas chromatography.
C, H, N and S are determined simultaneously whereas O is analysed by pyrolysis in the next step. The CHNS content of a sample is determined by weighing the sample and wrapping it in tin boats and for oxygen silver boats. High temperature combustion of the sample (1150°C for CHNS analysis) in an oxygen rich environment oxidizes the sample, this is followed by controlled reduction of the gasses formed during combustion.
Through this process any carbon contained in the sample is converted to CO2, hydrogen to H20, nitrogen to N2 and sulphur to SO2.
The sample can be either solid or liquid, but water in the sample affects the result. In the case of aqueous samples, it is possible to dry the sample before analysis.