This method is for determining basic nitrogen in liquefied petroleum gas (LPG). The method determines basic nitrogen species that are extractable by aqueous acid, including ammonia and alkyl amines, which typically adsorb on the stainless steel surface of a LPG cylinder. This method is limited to ammonia, primary amines containing four or less carbon atoms, secondary amines containing eight or less carbon atoms and tertiary amines with nine or less carbon atoms. All linear aliphatic substituents of the amine analytes must contain less than five carbon atoms. Combined nitrogen can be determined using UOP Method 936. Nitriles are not detected by this method. Amides and/or ionic sodium, if present at a concentration of 10 mass-ppm or greater, will interfere with the quantitation of ammonia. Potassium ions in the acid extract can also interfere with the detection of methylamine and ethylamine. The procedure yields quantitative basic nitrogen results in the range of 0.1 mass-ppm to 3 mass-%.
Citing ASTM Standards
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