Carbon, Hydrogen and Nitrogen Analysis
Analysis for carbon, hydrogen and nitrogen is conducted in an elemental analyzer that burns a small portion of sample in an oxygen atmosphere to create the combustion byproducts CO2, H2O and N2 (or NOx). The gases are then separated and quantified by either an infrared cell or a thermal conductivity detector. Results are reported in wt % of the corresponding element.
Samples are prepared by weighing a sample portion into a capsule (typically made of tin foil), carefully crimping the capsule and then loading it into an auto sampler. Typical masses taken for this test are between 1 and 5 mg, though more may be taken for some instruments. The autosampler drops the sample capsule into a furnace where the combustion occurs.
In the case of samples that exhibit poor recovery of carbon, hydrogen or oxygen, a combustion aid, such as Vanadium Pentoxide, may be added to the sample before the capsule is crimped. Presence of this combustion aid improves the overall combustion of the sample and may improve recovery.
Galbraith Laboratories employs four different analytical methods for the determination of CHN. The methods are largely aligned with different models of Elemental Analyzers. Each of Galbraith’s methods are based on industry methods, but have extra QC requirements embedded to ensure the accuracy of results.
The methods are indicated below along with links to each method summary:
Analysis of Carbon, Hydrogen and Nitrogen
Samples are introduced into a furnace and are quantitatively combusted in an oxygen atmosphere. The instrument detects and quantifies the gaseous combustion byproducts: CO2, H2O and N2 (or NOx). Most instruments quantify each of the elements in every analysis, even if only one is desired.
Quantitation limit varies among the instruments. The range is 0.5%-1%. Results that are below the quantitation limit are reported as a less than value, i.e. <0.5%.
Results are reported in % (wt/wt) unless another unit is requested.