Funding support for this work was provided by the Defense Logistics Agency Energy (DLA Energy) and the Naval Air Systems Command (NAVAIR).
This research was performed while an author held an NRC Research Associateship award at the U.S. Naval Research Laboratory.

CAUTION: Please consult relevant safety data sheets (SDS) of all compounds before use. Appropriate safety practices are recommended. All work should be performed while wearing personal protective equipment such as gloves, safety glasses, lab coat, long pants, and closed-toed shoes. All standard and sample preparations should be done in a ventilated hood.
1. Preparation of standards
<ol>
	<li>Prepare a 5,000 mg/kg (ppm) solution of carbazole (calibration standard, minimum of 98% purity) by pl...

<ol>
	<li>Garner, M. W., Morris, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laboratory+Studies+of+Good+Hope+and+Other+Diesel+Fuel+Samples.">Laboratory Studies of Good Hope and Other Diesel Fuel Samples.</a> ARTECH Corp. Report No. J8050.93-FR. , (1982).</li><li>Morris, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fleet+Fuel+Stability+Analyses+and+Evaluations.">Fleet Fuel Stability Analyses and Evaluations.</a> ARTECH Corp. Report No. DTNSRDC-SME-CR-01083. , (1983).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+F-76+Fuels+from+the+Western+Pacific+Region+Sampled+in+2014.">Analysis of F-76 Fuels from the Western Pacific Region Sampled in 2014.</a> Naval Research Laboratory Letter Report 6180/0012A. , (2015).</li><li>Westbrook, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+F-76+Fuel,+Sludge,+and+Particulate+Contamination.">Analysis of F-76 Fuel, Sludge, and Particulate Contamination.</a> Southwest Research Institute Letter Report. Project No. 08.15954.14.001. , (2015).</li><li>Morris, R. E., Loegel, T. N., Cramer, J. A., Leska Myers, K. M., A, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Examination+of+Diesel+Fuels+and+Insoluble+Gums+in+Retain+Samples+from+the+West+Coast-Hawaii+Region.">Examination of Diesel Fuels and Insoluble Gums in Retain Samples from the West Coast-Hawaii Region.</a> Naval Research Laboratory Memorandum Report. No. NRL/MR/6180-15-9647. , (2015).</li><li>Maciel, G. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantification+of+Nitrogen+Compounds+in+Diesel+Fuel+Samples+by+Comprehensive+Two-Dimensional+Gas+Chromatography+Coupled+with+Quadrupole+Mass+Spectrometry.">Quantification of Nitrogen Compounds in Diesel Fuel Samples by Comprehensive Two-Dimensional Gas Chromatography Coupled with Quadrupole Mass Spectrometry.</a> Journal of Separation Science. 38 (23), 4071-4077 (2015).</li><li>Deese, R. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+Organic+Nitrogen+Compounds+and+Their+Impact+on+the+Stability+of+Marginally+Stable+Diesel+Fuels.">Characterization of Organic Nitrogen Compounds and Their Impact on the Stability of Marginally Stable Diesel Fuels.</a> Energy &amp; Fuels. 33 (7), 6659-6669 (2019).</li><li>Lissitsyna, K., Huertas, S., Quintero, L. C., Polo, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+Simple+Method+for+Quanitation+of+Nitrogen+Compounds+in+Middle+Distillates+using+Solid+Phase+Extraction+and+Comprehensive+Two-Dimensional+Gas+Chromatography.">Novel Simple Method for Quanitation of Nitrogen Compounds in Middle Distillates using Solid Phase Extraction and Comprehensive Two-Dimensional Gas Chromatography.</a> Fuel. 104, 752-757 (2013).</li><li>Machado, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comprehensive+two-dimensional+gas+chromatography+for+the+analysis+of+nitrogen-containing+compounds+in+fossil+fuels:+A+review.">Comprehensive two-dimensional gas chromatography for the analysis of nitrogen-containing compounds in fossil fuels: A review.</a> Talanta. 198, 263-276 (2019).</li><li>Adam, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+Benchmark+for+Basic+and+Neutral+Nitrogen+Compounds+Speciation+in+Middle+Distillates+using+Comprehensive+Two-Dimensional+Gas+Chromatography.">New Benchmark for Basic and Neutral Nitrogen Compounds Speciation in Middle Distillates using Comprehensive Two-Dimensional Gas Chromatography.</a> Journal of Chromatography A. 1148, 55-65 (2007).</li><li>Wang, F. C. Y., Robbins, W. K., Greaney, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Speciation+of+Nitrogen-Containing+Compounds+in+Diesel+Fuel+by+Comprehensive+Two-Dimensional+Gas+Chromatography.">Speciation of Nitrogen-Containing Compounds in Diesel Fuel by Comprehensive Two-Dimensional Gas Chromatography.</a> Journal of Separation Science. 27, 468-472 (2004).</li><li>Yan, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sulfur+and+Nitrogen+Chemiluminescence+Detection+in+Gas+Chromatographic+Analaysis.">Sulfur and Nitrogen Chemiluminescence Detection in Gas Chromatographic Analaysis.</a> Journal of Chromatography A. 976 (1), 3-10 (2002).</li></ol>

The purpose of this method is to provide detailed information on the nitrogen content of diesel and jet fuels without extensive sample preparation such as liquid extractions. This is achieved by pairing a two dimensional GC system (GCxGC) with a nitrogen-specific detector (nitrogen chemiluminescence detector, NCD). The GCxGC provides significant separation of the compounds relative to traditional one-dimensional GC. The NCD provides trace nitrogen compound detection without any background interferences. Other nitrogen-sp...

Before use, fuels undergo extensive quality assurance and specification testing by refineries to verify that the fuel they are producing will not fail or cause equipment problems once disseminated. These specification tests include flash point verification, freeze point, storage stability, and many more. The storage stability tests are important as they determine if the fuels have a tendency to undergo degradation during storage, resulting in the formation of gums or particulates. There have been incidences in the past when F-76 diesel fuels have failed during storage even though they passed all specification tests1. These failures resulted in high concentrations of particulate matter in the fuels that could be detrimental to equipment such as fuel pumps. The extensive research investigation that followed this discovery suggested that there is a causal relationship between certain types of nitrogen compounds and the particulate formation2,3,4,5. However, many of the techniques used to measure nitrogen content are strictly qualitative, require extensive sample preparation, and provide little information on the identity of the suspect nitrogen compounds. The method described herein is a two-dimensional GC (GCxGC) method paired with a nitrogen chemiluminescence detector (NCD) that was developed for the purpose of characterizing and quanitifying trace nitrogen compounds in diesel and jet fuels.
Gas chromatography is used extensively in petroleum analyses and there are over sixty published ASTM petroleum methods associated with the technique. A wide range of detectors are combined with gas chromatography such as mass spectrometry (MS, ASTM D27896, D57697), Fourier-transform infrared spectroscopy (FTIR, D59868), vacuum ultraviolet spectroscopy (VUV, D80719), flame ionization detector (FID, D742310), and chemiluminesence detectors (D550411, D780712, D4629-1713). All these methods can provide significant compositional information about a fuel product. Since fuels are complex sample matrices, gas chromatography enhances compositional analysis by separating out sample compounds based on boiling point, polarity, and other interactions with the column.
To further this separation ability, two-dimensional gas chromatography (GCxGC) methods can be utilized to provide compositional maps by using sequential columns with orthogonal column chemistries. Separation of compounds occur both by polarity and boiling point, which is a comprehensive means to isolate fuel constituents. Although it is possible to analyze nitrogen-containing compounds with GCxGC-MS, the trace concentration of the nitrogen compounds within the complex sample inhibits identification14. Liquid-liquid phase extractions have been attempted in order to use GC-MS techniques; however, it was found that the extractions are incomplete and exclude important nitrogen compounds15. Additionally, others have used solid phase extraction to enhance the nitrogen signal while reducing the potential for the fuel sample matrix interference16. However, this technique has been found to irreversible retail certain nitrogen species, especially low molecular weight nitrogen-bearing species.
The nitrogen chemiluminescence detector (NCD) is a nitrogen-specific detector and has been successfully used for fuel analyses17,18,19. It utilizes a combustion reaction of nitrogen-containing compounds, the formation of nitric oxide (NO), and a reaction with ozone (see Equations 1 &#38; 2)20. This is accomplished in a quartz reaction tube that contains a platinum catalyst and is heated to 900 &#176;C in the presence of oxygen gas.
The photons emitted from this reaction are measured with a photomultiplier tube. This detector has a linear and equimolar response to all nitrogen-containing compounds because all nitrogen-containing compounds are converted to NO. It is also not prone to matrix effects because other compounds in the sample are converted to non-chemiluminescence species (CO2 and H2O) during the conversion step of the reaction (Equation 1). Thus, it is an ideal method for measuring nitrogen compounds in a complex matrix such as fuels.
<img src="/files/ftp_upload/60883/60883eq1a.jpg" />
The equimolar response of this detector is important for nitrogen compound quantitation in fuels because the complex nature of fuels does not allow for calibration of each nitrogen analyte. The selectivity of this detector facilitates the detection of trace nitrogen compounds even with a complex hydrocarbon background.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>10 &#181;L syringe</td>
			<td>Agilent</td>
			<td></td>
			<td>gold series</td>
		</tr>
		<tr>
			<td>180 &#181;m x 0.18 &#181;m Secondary Column</td>
			<td>Restek</td>
			<td>Rxi-1MS</td>
			<td>nonpolar phase column, crossbond dimethyl polysiloxane</td>
		</tr>
		<tr>
			<td>250 &#181;m x 0.25 &#181;m Primary Column</td>
			<td>Restek</td>
			<td>Rxi-17SilMS</td>
			<td>midpolarity phase column</td>
		</tr>
		<tr>
			<td>Autosampler tray and tower</td>
			<td>Agilent</td>
			<td>7963A</td>
			<td></td>
		</tr>
		<tr>
			<td>Carbazole</td>
			<td>Sigma</td>
			<td>C5132</td>
			<td>98%</td>
		</tr>
		<tr>
			<td>Diethylaniline</td>
			<td>Aldrich</td>
			<td>185898</td>
			<td>&#8805; 99%</td>
		</tr>
		<tr>
			<td>Dimethylindole</td>
			<td>Aldrich</td>
			<td>D166006</td>
			<td>97%</td>
		</tr>
		<tr>
			<td>Duel Loop Thermal Modulator</td>
			<td>Zoex Corporation</td>
			<td>ZX-1</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethylcarbazole</td>
			<td>Aldrich</td>
			<td>E16600</td>
			<td>97%</td>
		</tr>
		<tr>
			<td>Gas chromatograph</td>
			<td>Agilent</td>
			<td>7890B</td>
			<td></td>
		</tr>
		<tr>
			<td>GC vials</td>
			<td>Restek</td>
			<td>21142</td>
			<td></td>
		</tr>
		<tr>
			<td>GCImage Software, Version 2.6</td>
			<td>Zoex Corporation</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Indole</td>
			<td>Aldrich</td>
			<td>13408</td>
			<td>&#8805; 99%</td>
		</tr>
		<tr>
			<td>Isopropyl Alcohol</td>
			<td>Fisher Scientific</td>
			<td>A461-500</td>
			<td>Purity 99.9%</td>
		</tr>
		<tr>
			<td>Methylaniline</td>
			<td>Aldrich</td>
			<td>236233</td>
			<td>&#8805; 99%</td>
		</tr>
		<tr>
			<td>Methylquinoline</td>
			<td>Aldrich</td>
			<td>382493</td>
			<td>99%</td>
		</tr>
		<tr>
			<td>Nitrogen Chemiluminescence Detector</td>
			<td>Agilent</td>
			<td>8255</td>
			<td></td>
		</tr>
		<tr>
			<td>Pyridine</td>
			<td>Sigma-Aldrich</td>
			<td>270970</td>
			<td>anhydrous, 99.8%</td>
		</tr>
		<tr>
			<td>Quinoline</td>
			<td>Aldrich</td>
			<td>241571</td>
			<td>98%</td>
		</tr>
		<tr>
			<td>Trimethylamine</td>
			<td>Sigma-Aldrich</td>
			<td>243205</td>
			<td>anhydrous, &#8805; 99%</td>
		</tr>
	</tbody>
</table>

nitrogen compound characterization in fuels by multidimensional gas chromatography

Certain nitrogen-containing compounds can contribute to fuel instability during storage. Hence, detection and characterization of these compounds is crucial. There are significant challenges to overcome when measuring trace compounds in a complex matrix such as fuels. Background interferences and matrix effects can create limitations to routine analytical instrumentation, such as GC-MS. In order to facilitate specific and quantitative measurements of trace nitrogen compounds in fuels, a nitrogen-specific detector is ideal. In this method, a nitrogen chemiluminescence detector (NCD) is used to detect nitrogen compounds in fuels. NCD utilizes a nitrogen-specific reaction that does not involve the hydrocarbon background. Two-dimensional (GCxGC) gas chromatography is a powerful characterization technique as it provides superior separation capabilities to one-dimensional gas chromatography methods. When GCxGC is paired with a NCD, the problematic nitrogen compounds found in fuels can be extensively characterized without background interference. The method presented in this manuscript details the process for measuring different nitrogen-containing compound classes in fuels with little sample preparation. Overall, this GCxGC-NCD method has been shown to be a valuable tool to enhance the understanding of the chemical composition of nitrogen-containing compounds in fuels and their impact on fuel stability. The % RSD for this method is &#60;5% for intraday and &#60;10% for interday analyses; the LOD is 1.7 ppm and the LOQ is 5.5 ppm.

The nitrogen-containing compound, carbazole, was used in this method as the calibration standard. Carbazole elutes at approximately 33 min from the primary column and at 2 s from the secondary column. These elution times will vary slightly depending on the exact column length and instrumentation. In order to obtain a proper calibration curve and, subsequently, good quantitation of nitrogen compounds within a sample, the calibration peaks should not be overloaded nor have any nitrogen cont...

Watch this Scientific Journal Video about Nitrogen Compound Characterization in Fuels by Multidimensional Gas Chromatography at JoVE.com

Nitrogen Compound Characterization in Fuels by Multidimensional Gas Chromatography

Here, we present a method utilizing two-dimensional gas chromatography and nitrogen chemiluminescence detection (GCxGC-NCD) to extensively characterize the different classes of nitrogen-containing compounds in diesel and jet fuels.

Certain nitrogen-containing compounds can contribute to fuel instability during storage. Hence, detection and characterization of these compounds is ...

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7.5K Views.  U.S. Naval Research Laboratory. Here, we present a method utilizing two-dimensional gas chromatography and nitrogen chemiluminescence detection (GCxGC-NCD) to extensively characterize the different classes of nitrogen-containing compounds in diesel and jet fuels.