Spectrophotometric Determination of Total Nitrogen in Oils

Abstract

It is frequently necessary to analyze petroleum feed stocks and products for small amounts (less than 0.1%) of combined nitrogen. The conventional macro-Kjeldahl method requires large samples, prolonged acid digestion, and large amounts of reagents. A semimicro-Kjeldahl procedure has been devised to use small samples and to allow the determination of very low concentrations of nitrogen. The oil samples are digested with acid in special Kjeldahl flasks which fit onto an all-glass apparatus for steam distillation of the ammonia. The ammonia is determined by spectrophotometric measurements of the color developed with Nessler's reagent. Nitrogen present as amino, nitro, nitroso, azo, and ring compounds can be determined on an average to *10% over a concentration range of 0.002 to 1.0%.

Determination of Total Nitrogen in Reformer Charge Stock

“…by the furnace, L. The products of the catalytic reaction are swept into the absorber, P, where ammonia is scrubbed out and retained. The ammonia is then determined colorimetrically with Kessler's reagent (1,9).…”

Petroleum

“…Shepherd (140) reported the results of cooperative analyses by 51 laboratories, comparing conventional volumetric chemical methods with mass spectrometry on a sample of carbureted water gas. Tickner and Lossing (153) used the mass spectrometer to determine vapor pressure of hydrocarbons of low vapor pressure; the more conventional methods are subject to large errors due to traces of volatile impurities, whereas analysis by the mass spectrometer provides information for correcting for the partial pressures of the interfering impurities.…”

Light Absorption Spectrometry

“…Clarke (29) improved the mercuric nitrate-diphenylcarbazone method for chloride in water. Hale et al (71) determined nitrogen in petroleum products.…”