EXPLANATION
This is the only ASTM method for simultaneous determination of carbon, hydrogen, and nitrogen in petroleum products and lubricants. There are at least three instrumental techniques available for this analysis, each based on different chemical principles. However, all involve sample combustion, components separation, and final detection. These test methods are applicable to lubricating oils, crude oils, additives, and residues. These test methods were tested in the concentration range of at least 75 to 87 mass % for carbon, at least 9 to 16 mass % for hydrogen, and 0.1 to 2 mass % for nitrogen. The nitrogen method is not applicable to light materials or to samples containing <0.75 mass % nitrogen, or both, such as gasoline, jet fuel, naptha, diesel fuel, or chemical solvents. These test methods are not recommended for the analysis of volatile materials such as gasoline, gasoline oxygenate blends, or aviation turbine fuels.
TEST SUMMARY
In Test Method A, a sample is combusted in an oxygen atmosphere, and the product gases are separated from each other by adsorption over chemical agents. The remaining elemental nitrogen gas is measured by a thermal conductivity cell. Carbon and hydrogen are separately measured by selective infrared cells as carbon dioxide and water.
In Test Method B, a sample is combusted in an oxygen atmosphere, and the product gases are separated from each other and the three gases of interest are measured by gas chromatography.
In Test Method C, a sample is combusted in an oxygen atmosphere, and the product gases are cleaned by passage over chemical agents. The three gases of interest are chromatographically separated and measured with a thermal conductivity detector.
TEST PRECISION
This test method has no relative bias among three procedures.