Speciation of nitrogen compounds in gasoline and diesel range process streams by capillary column gas chromatography with chemiluminescence detection

This paper describes the development of a gas chromatographic method that uses nitrogen-specific detection based on chemiluminescence. A highly sensitive nitrogen-specific detector (Antek 705D) coupled to a Hewlett-Packard gas chromatograph is optimized to speciate nitrogen compounds in gasoline and diesel range process streams. Under optimized conditions, the nitrogen-to-carbon selectivity is greater than 106. The nitrogen chemiluminescence detector (NCD) provides a uniform response to different classes of nitrogen compounds and can detect concentration of individual components down to 100 ppb nitrogen. The detector's linear response in a range of 0.2 to 54 ppm nitrogen for an individual nitrogen component is established using several aliphatic and aromatic nitrogen-containing compounds. Gasoline and diesel range streams containing any level of total nitrogen can be analyzed after appropriate dilution so that each nitrogen component is below 50 ppm. In addition to the nitrogen speciation, total nitrogen can simultaneously be determined with reasonable accuracy using the NCD system. The repeatability and accuracy of the nitrogen quantitation is found to be within 7% at the 95% confidence level based on six to seven measurements.