CHN TOTAL CARBON, HYDROGEN & NITROGEN
- Samples weighed precisely into tin capsules and dropped at pre-set times into combustion tube (at 1000°C). A constant stream of helium is maintained through the tube.
- Helium stream replaced by pure oxygen for a brief period prior to sample introduction.
- Sample instantaneously burned (flash combustion) followed by intense oxidation of tin capsule at 1800°C.
- Resulting combustion gases passed over catalysts to ensure complete oxidation and absorption of halogens, sulfur and other interferences.
- Gases are then separated on chromatographic column into N, C, and H. These gases are quantitatively measured by a thermal conductivity detector.
This technique is generally free of interferences
- A few silicon and organo-metallic compounds exhibit a tendency to form stable carbides.
- Samples containing phosphorus may not combust successfully and give low carbon values.
- The analysis of numerous fluorine containing compounds will cause errors in the hydrogen result.
All the above problems can be remedied with the addition of additives to the sample.