Elemental Analysis for C, H, N, S and O
Description of method
The elemental analyzer is used for the determination of the carbon, hydrogen, nitrogen and sulphur content of organic and many inorganic samples.
Procedure in C,H,N,S mode:
The sample is transferred into a combustion tube and then burned in an atmosphere enriched in oxygen. A carrier gas flow transfers the combustion products, arising from this process, like CO2, H2O, NOx and SOx to a WO3 granulate, placed in the combustion tube. The WO3 granulate delivers catalytic oxidation and binds disturbing alkali and earth alkali elements.
During the next step the carrier gas transfers the gaseous combustion products into the reduction tube, which is filled with copper, for the reduction of NOx to N2 and SOx to SO2. The reduction tube contains silverwool which is used to remove volatile halogen compounds.
The gas mixture is separated in its components via three adsorption columns. N2 is not adsorbed and is the first component which enters the thermal conductivity detector, while CO2, H2O and SO2 are adsorped at specific adsorption columns. CO2, H2O and SO2 are then sequentially thermally desorped and detected.
The absolute element content is computed from the integrals of the individual measured peaks and the calibration factors.
Procedure in C,H,N mode:
In contrast to C,H,N,S mode the combustion tube is filled with CuO, which promotes the combustion of samples difficult to combust and with lead chromate that adsorbs SOx.
Procedure in O mode:
The substance to be analyzed is digested by means of pyrolysis in a reductive atmosphere at a temperature of approx. 1150 °C. The oxygen radicals formed in the pyrolysis tube are converted quantitatively at a carbon contact into CO. The gas mixture contains CO and by-products. CO is separated and measured via a thermal conductivity detector. The absolute element content is computed from the integrals of the individual measured peaks and the calibration factors.