ASTM D4629 Standard Test Method for Trace Nitrogen in Liquid Hydrocarbons by Oxidative Combustion and Chemiluminescence Detection

The ASTM D4629 standard describes a standard method for determining organically bound nitrogen in the range of 0.3 to 100 mg/kg total nitrogen (N) in liquid hydrocarbons. The measurement method is applicable to liquid samples such as naphtha, distillates, and oils with a boiling point between 50 and 400 °C and a viscosity between 0.2 and 10 mm²/s (cSt). Samples with levels higher than 100 mg/kg N should be diluted with a suitable solvent before analysis or, alternatively, processed according to ASTM D5762.

In the method described in ASTM D4629, the liquid hydrocarbon sample is transferred into the combustion tube of the analyzer either directly with a syringe or with the aid of a boat inlet. This occurs within an inert gas stream (argon). The sample is evaporated and combusted in the presence of oxygen at high combustion temperatures to form a mixture of nitrogen monoxide and nitrogen dioxide, NOx. A converter then quantitatively turns NO₂ into NO. The NO reacts with ozone, resulting in an excited state of NO₂*. When this state decays, light is emitted. This effect is known as chemiluminescence. The light, whose intensity is a direct measure of the nitrogen contained in the sample, is detected by a photomultiplier.

Even the slightest traces of nitrogen compounds can act as catalyst poisons in hydrogenation processes in refineries and the chemical industry, thus noticeably decreasing the service life and efficiency of the catalysts and causing the formation of undesirable byproducts such as amines. This not only influences process safety, but also the quality of the end products. To prevent this, strict control of the entire production process is required. 

ASTM D4629 is the ideal choice for this purpose. It can be used equally well for determination of bound nitrogen in precursor materials and in process streams, as well as for quality control of the end products.

Analytik Jena offers high-performance solutions for measuring trace nitrogen in petrochemicals and other hydrocarbons in accordance with ASTM D4629. The multi EA 5100 and the compEAct series are designed to measure nitrogen levels in the trace range. Thanks to their high level of automation, they guarantee maximum sample throughput.

Our solutions for ASTM D4629

Sources

• ASTM D4629-17 - Standard Test Method for Trace Nitrogen in Liquid Hydrocarbons by Syringe/Inlet Oxidative Combustion and Chemiluminescence Detection