Basic Nitrogen-containing Compounds Research Articles

Understanding the demetallization of nitrogen-rich hydrothermal liquefaction biocrudes by FTICR mass spectrometry: Recalcitrant effect of metalloporphyrins and basic nitrogenates

Higher metallic content in nitrogen-rich hydrothermal liquefaction (HTL) biocrudes is a bottleneck during downstream hydroprocessing, which is necessary for producing drop-in biofuels from urban residues and algal feedstocks. Therefore, this work explores a non-catalytic pathway for effective demetallization of nitrogen-rich HTL biocrudes obtained from sewage sludge and cyanobacteria (generally referred as Spirulina algae). Herein, we utilized five different organic/inorganic acids and comprehensively documented the effect of acid washing on basic nitrogen containing compounds (NCCs), oxygenates and organometallics. HTL biocrudes before and after acid washing were characterized by Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (MS). FTICR MS showed the presence of iron porphyrins in cyanobacteria biocrude, whereas no sign of metalloporphyrins was observed in sludge biocrude. Moreover, cyanobacteria biocrude mostly contains basic NCCs (N1 and N2 species), whereas sludge biocrude apart from basic NCCs mostly contain fatty acids (O2 and O4 species). Due to the presence and absence of metalloporphyrins, acid washing (0.1 M H2SO4) showed ineffective demetallization (3.2 %) for cyanobacteria and effective demetallization 89.2 % for sludge biocrude. For cyanobacteria, 66.3 % demetallization was achieved at 10 M H2SO4 which not only degrades the biocrude but also accounts for 35 % organic loss. However, O1-O4 species in sludge biocrude represent acidic groups such as carboxyl groups; thereby, 20.1 % organic loss is encountered even at 0.1 M H2SO4. For both biocrudes denitrogenation via acid washing remains unfeasible due to high organic loss. Present results indicate that a priori information about organometallics, NCCs, and oxygenates in a given biocrude could provide guidance to select and further optimize the demetallization process.

Modeling Reactive Ammonia Uptake by Secondary Organic Aerosol in a Changing Climate: A WRF-CMAQ Evaluation

In addition to the well-constrained inorganic acid-base chemistry of ammonia resulting in fine particulate matter (PM2.5) formation, ammonia also reacts with certain organic compounds in secondary organic aerosol (SOA) to produce less basic nitrogen-containing organic compounds. In this study, the potential meteorology and air quality impacts of the heterogeneous uptake of NH3 by SOA are investigated using the WRF-CMAQ two-way coupled model, which calculates the two-way radiative forcing feedback caused by aerosol between meteorology and chemistry in a single simulation. Simulations with and without the NH3-SOA uptake are performed over the contiguous US for July 2014 and July 2050 under the RCP 8.5 IPCC scenario to study the potential impact of climate change. A comparison with multiple observation network data shows that the NH3-SOA uptake improves the model performance for PM2.5 prediction (bias reduced from −22% to −17%), especially the underestimation of organic carbon over the Southeastern US (bias reduced from −17% to −7%). Secondly, the addition of the NH3-SOA chemistry significantly impacts the concentration of NH3 and NH4+, thus affecting the modeled particle acidity. Including the NH3-SOA uptake also impacts the meteorological conditions through the WRF-CMAQ two-way feedback. Moreover, the impact on meteorological conditions results in different windspeed or dispersion conditions, thus affecting air quality predictions. Finally, simulations including the NH3-SOA uptake under the warmer climate conditions of 2050 show a smaller impact on air quality predictions than it does under current climate conditions. This study confirms the importance and necessity of including NH3-SOA chemistry in air quality predictions.

Newly reported alkaloids produced by marine-derived Penicillium species (covering 2014-2018).

Alkaloids, especially heterocyclic alkaloids, have received remarkable attention due to their intriguing structures and potential pharmacological activities. The marine fungi residing in extreme environmental conditions are among the richest sources of these basic nitrogen-containing compounds. Fungal species belonging to the genus Penicillium have been studied worldwide for their biosynthetic potential for generating bioactive alkaloids. This paper offers a systematic review of the newly reported alkaloids produced by marine-derived Penicillium species over the past five years (covering the literature from the beginning of 2014 through the end of 2018) and describes the structural diversity, biological activities, and plausible biosynthetic pathway of the reported compounds. A total of 106 alkaloids and 81 references are included in this review, which is expected to be beneficial for drug development and biosynthesis in the near future.

Adsorption kinetics in removal of basic nitrogen-containing compounds from practical heavy oils by amorphous silica-alumina

The adsorption behavior of basic compounds in practical vacuum gas oil is quantitatively analyzed on amorphous silica-alumina with acid sites, mesopores and thermal stability. Time course of adsorption capacity was found to be controlled by kinetics but not by equilibrium. The rate of adsorption was found to have pseudo second-order but not pseudo first-order kinetics, indicating that the adsorption rate was mainly controlled by the diffusion of large molecules. The particle size did not influence the adsorption quantity at equilibrium, whereas the smaller particle size increased the adsorption rate. The adsorption quantity at equilibrium was influenced by the molecular structure of basic compound due to steric hinderance around the basic site, whereas the adsorption rate strongly depended on the molecular size, supporting that the adsorption rate was mainly controlled by the diffusion of compounds in the pores of amorphous silica-alumina. Comparison of solvents showed that the adsorption quantity at equilibrium was influenced by the polarity but not by the molecular size, while the adsorption rate strongly depended on both the polarity and molecular size. The reusability of adsorbent silica-alumina was demonstrated by the stable adsorption capacity and rate after calcination for the regeneration.

Characterization of heteroatom distributions in the polar fraction of North Sea oils using high-resolution mass spectrometry

Resins are a sub-fraction of crude oil consisting of heteroatom-containing polar compounds. These species are of key importance in oil recovery, oil fluid thermodynamic properties, refining processes and for the environmental impact of petroleum production. Due to the inherent complexity of crude oil, little is known of the absolute molecular structure of these compounds. Here we show how a combination of separation science and mass spectrometry reveal the compositional space of resins isolated from Danish North Sea crudes. By employing spectral stitching mass spectrometry, we resolve over 15,000 unique peaks, an increase of 50% compared to broadband acquisition. The results indicate that the dominant component of North Sea resins are basic nitrogencontaining compounds with small to medium sized aromatic cores. Using chemometric data treatment it becomes evident that each field displays unique profiles, and that these fractions can be used for oil-oil and oil-source correlations. Further, a more detailed knowledge of their composition will allow us to gain a better understanding of the interactions between resins, hydrocarbons and reservoir rock material. Improved understanding of rock-fluid and fluid-fluid interactions is key for development and understanding of improved recovery mechanisms for tight chalk reservoirs.

Evaluation of the effects of the simulated thermal evolution of a Type-I source rock on the distribution of basic nitrogen-containing compounds

Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) allows the molecular-level characterization of ultracomplex mixtures such as crude oil samples. By combining FT-ICR MS with electrospray ionization, a myriad of polar compounds can routinely be identified and assigned with unmatched mass resolution and accuracy. The profile of polar compounds containing NSO atoms can be used to track and evaluate important parameters of crude oil. Recently, using ESI FT-ICR MS in the negative mode (https://doi.org/10.1016/j.orggeochem.2017.10.004), we investigated changes in the profile of polar compounds as a function of thermal maturity. Sulfur-containing compounds are completely destroyed during maturation, and the relatively high content of O-containing compounds decreases via decarboxylation and dehydration. The number of double bond equivalents (DBE) increased, indicating the occurrence of aromatization and condensation. However, the carbon number distribution shifted to lower values as a function of thermal maturity. Six regressions based on changes in the contents of O2 compounds were proposed as maturity parameters. Here, by focusing on tracking and evaluating the impact of thermal maturity on basic polar compounds, a set of hydrous pyrolysis (HP) products was analyzed using an ESI(+) 7.2 T LTQ FT-ICR MS system. The samples at various stages of maturity consist of one immature bitumen (original sample), eleven expelled oil samples and eight residual bitumen samples. Determining the changes in the contents of N- and NO-containing compounds with maturity allows us to propose new parameters for assessing thermal maturity that cover the full window of oil generation.

Phytic acid-encapsulated MIL-101(Cr): Remarkable adsorbent for the removal of both neutral indole and basic quinoline from model liquid fuel

Phytic acid (PA) encapsulated metal-organic framework (MIL-101(Cr) or Cr-benzenedicarboxylate) was prepared for the first time; and applied in the adsorptive removal of nitrogen-containing compounds (NCCs) from liquid model fuel. The modified MIL-101(Cr)s resulted in very promising maximum adsorption capacities (Q0) for both the neutral indole (IND, Q0 = 543 mg/g) and basic quinoline (QUI, Q0 = 549 mg/g) compared to the pristine MIL-101(Cr) (IND; Q0 = 416 mg/g; QUI, Q0 = 409 mg/g). Or, the Qo values of PA(3)@MIL-101(Cr) for the adsorptions of IND and QUI stand at the second and fifth positions, respectively, among any previously reported results. Moreover, the new adsorbent showed around 8 times adsorption capacity to that of conventional activated carbon. PA encapsulation onto MIL-101(Cr) resulted in 86% and 91% increased adsorption (based on unit surface area of adsorbent) of IND and QUI, respectively. Moreover, PA(3)@MIL-101(Cr) showed more effective/selective adsorption than pristine MIL-101(Cr) towards the NCCs especially when toluene (as aromatics) was added as co-solvent. The extraordinary adsorptions could be described by the hydrogen bonding and the acid-base interactions between the NCCs and the PA functionalities of the adsorbents. Moreover, the PA@MIL-101(Cr)s could be regenerated via a simple manner and reused in adsorptions up to several cycles. Therefore, the novel PA@MOF materials could be suggested as a type of very efficient adsorbents for the adsorptive removal of both neutral and basic NCCs from liquid model fuel.

High Capacity Oil Denitrogenation over Azine- and Tetrazine-Decorated Metal-Organic Frameworks: Critical Roles of Hydrogen Bonding.

In this work, we demonstrate that rational decoration of pore walls of the metal-organic frameworks (MOFs) with azine and dihydro-tetrazine functions is a very practical strategy for high capacity removal of both neutral and basic nitrogen-containing compounds (NCCs) from model oil. Its performance is even much better than the MOFs with high surface area, open metal sites, and different functional groups such as amine, hydroxyl, carboxy, and sulfonate. For this aim, a number of isostructure functional MOFs (FMOFs) have been synthesized. Among them, TMU-5 (with formula [Zn(OBA)(BPDH)0.5] n·1.5DMF, where H2OBA = 4,4'-oxybis(benzoic acid) and BPDH = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene) and TMU-34 (with formula [Zn(OBA)(H2DPT)0.5] n·DMF H2DPT = 3,6-di(pyridin-4-yl)-1,4-dihydro-1,2,4,5-tetrazine) show high affinity toward neutral and basic NCCs, respectively. Dihydro-tetrazine-decorated TMU-34 shows good affinity toward basic NCCs [pyridine (PYD) and quinoline (QUI)] because of hydrogen bonding of dihydro-tetrazine (-NH)···(N) basic NCCs. TMU-34 can adsorb about 619 and 632 mg g-1 PYD and QUI, respectively. On the other hand, azine-methyl-functionalized TMU-5 shows very high affinity to neutral NCCs [pyrrole (PRR) and indole (IND)] owing to strong hydrogen bonding of azine-methyl (Me-C═N-N═C-Me)···(NH) neutral NCCs. TMU-5 can adsorb 518 and 578 mg g-1 PRR and IND, respectively. These numbers are among the best reported data in this area and even reveal higher significance of the host-guest interaction when we consider moderate surface of these FMOFs. These results have been achieved by our "application-directed cavity functionalization" approach through decoration of MOF structures by suitable organic functional groups for specific purposes.

Safety issues of methylglyoxal and potential scavengers

The health safety of methylglyoxal (MGO) has been recognized as a key issue owing to its ultra-high reactivity toward some key biomolecules such as amino acids, proteins, DNA, sulfhydryl- and basic nitrogen-containing compounds, including amino-bearing neurotransmitters. In this review, we have summarized the endo- and exogenous sources of MGO and its accumulation inside the body due to high intake, abnormal glucose metabolism and or malfunctioning glyoxalases, and review the debate concerning the adverse functionality of MGO ingested from foods. Higher than normal concentrations of MGO in the circulatory system and tissues have been found to be closely associated with the production of advanced glycation end products (AGEs), increased oxidative stress, elevated inflammation and RAGE (AGE receptors) activity, which subsequently progresses to a pathological stage of human health, such as diabetes complications, cancer, cardiovascular and degenerative diseases. Having illustrated the mechanisms of MGO trapping <i>in vivo</i>, we advocate the development of efficient and efficacious MGO scavengers, either assisting or enhancing the activity of endogenous glyoxalases to facilitate MGO removal, or providing phytochemicals and functional foods containing them, or pharmaceuticals to irreversibly bind MGO and thus form MGO-complexes that are cleared from the body.

Effective adsorptive removal of indole from model fuel using a metal-organic framework functionalized with amino groups

Nitrogen-containing compounds (NCCs) should be removed from fuels because of the negative effect of NCCs on the environment and catalyst stability. NCCs are composed of basic materials such as quinoline (QUI) and neutral materials such as indole (IND). The NCCs can be removed by various methods including adsorption. Compared with basic NCCs, neutral NCCs are more difficult to remove through adsorption due to their less affinity toward adsorbents. In this report, adsorption of IND (as one of the representative neutral NCCs) was studied over the metal-organic frameworks (MOFs), UiO-66 and UiO-66-NH2, which contain terephthalate and aminoterephthalate linkers, respectively. In spite of the reduced porosity of UiO-66-NH2, the adsorption capacity of IND was improved upto 46% when compared with pristine UiO-66. Therefore, the additional amino group in the MOF imparts extra adsorption capability on the MOF. For a detailed investigation, adsorption of other NCCs such as QUI, pyrrole, and methylpyrrole was studied. The improved adsorption of IND over amino-functionalized MOFs could be attributed to the improved interaction of IND with the MOF via H-bonding because of the NH2 group. In addition to this remarkable improvement in IND adsorption, UiO-66-NH2 could be regenerated several times for the adsorption of IND by simple solvent washing.

Characterization of Basic Nitrogen-Containing Compounds in the Products of Lube Base Oil Processing by Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

The distribution of basic nitrogen-containing compounds in three vacuum gas oils (VGOs) with different boiling ranges and their dewaxed oils from the lube base oil refining unit of a refinery were characterized by positive-ion electrospray ionization (ESI) Fourier transform-ion cyclotron resonance mass spectrometry (FTICR MS). It turned out that the composition of basic nitrogen compounds in the samples varied significantly in DBE and carbon number, and the dominant basic N-containing compounds in these oil samples were N1 class species. N1O1, N1O2, and N2 class species with much lower relative abundance were also identified. The composition of basic nitrogen compounds in VGOs and dewaxed VGOs were correlated with increased boiling point and varied in DBE and carbon numbers. The comparison of the analytical results between VGOs and dewaxed VGOs indicated that more basic N-containing compounds in VGO with low carbon number and small molecular weight tend to be removed by solvent refining in lube base oil processing.

Adsorptive denitrogenation of model fuels with porous metal-organic framework (MOF) MIL-101 impregnated with phosphotungstic acid: Effect of acid site inclusion

A metal-organic framework (MOF) MIL-101 was impregnated with phosphotungstic acid (PWA) and used as an adsorbent in liquid phase adsorption of nitrogen-containing compounds (NCCs) from a model fuel. The model fuel contained one sulfur-containing compound (SCC), benzothiophene (BT); one basic NCC, quinoline (QUI); and one neutral NCC, indole (IND). In both MIL-101 and PWA-impregnated MIL-101s, NCC adsorption selectivity was very high compared to the SCC selectivity. Additionally, the adsorption capacity of basic QUI increased by 20% with only 1% PWA impregnation in MIL-101. The adsorption of a neutral compound, IND, was slightly reduced with PWA impregnation in the MOF. The adsorption capacity/selectivity can be remarkably improved by a slight modification of MOFs, for example, to impart acidity. The MOF impregnated with PWA may be very interesting in commercial denitrogenation, especially for coal-derived fuels which contain mainly basic NCCs, by adsorption since the selectivity for NCCs (compared to SCCs) over the adsorbent is very high and the adsorbent can be reused many times.

Identification of several basic nitrogen-containing compounds in the presence of coextracted substances of urine and blood by capillary electrophoresis

Preparation conditions for samples of biological fluids (urine, blood) for electrophoretic identification of basic nitrogen-containing compounds with the aid of a Kapel-105 capillary electrophoresis system have been studied. It is demonstrated that bupivacaine, lidocaine, and azaleptine can be identified in biological fluids in the presence of coextracted substances using electrophoretic spectra and quantitative indices (pKa).

Analysis and Comparison of Nitrogen Compounds in Different Liquid Hydrocarbon Streams Derived from Petroleum and Coal

Identification and quantification of nitrogen compounds in five typical liquid hydrocarbon streams, including straight run gas oil, light cycle oil, and ultralow sulfur diesel derived from petroleum and coal liquids from the coal pyrolysis and the direct coal liquefaction, have been conducted by a combination of the modified solid phase extraction and gas chromatography with a mass spectrometry detector (GC−MS) and a nitrogen/phosphorus detector (GC−NPD). A simple and efficient method was applied for preisolating and concentrating the nitrogen compounds from the hydrocarbon matrix and coexisting oxygen-containing compounds. The identification and quantification results show that the coal-derived streams not only have much higher nitrogen content than the petroleum-derived ones but also contain quite different types of the nitrogen compounds. The major nitrogen compounds in the coal-derived streams are the basic nitrogen-containing compounds including aniline, quinoline, and their derivatives; while those in the petroleum-derived ones are the neutral nitrogen compounds, such as carbazole and its alkyl substituted derivatives. The implication of the analysis results on the fuel processing and deep denitrogenation is also discussed.

Atomic-scale insight into the origin of pyridine inhibition of MoS 2-based hydrotreating catalysts

Basic nitrogen-containing compounds such as pyridine are well known to be inhibitors of the hydrodesulfurization (HDS) reaction for the MoS 2-based catalysts. From an interplay of scanning tunneling microscopy (STM) experiments and density functional theory (DFT) calculations, atomic-scale insight into pyridine adsorption on MoS 2 is obtained. In agreement with previous IR-spectroscopy and DFT studies, the STM results show that the pyridine molecule itself interacts weakly or not at all with the MoS 2 nanoclusters. However, in the presence of hydrogen at the MoS 2 edges, adsorbed species are revealed by STM also at the edges. The calculated DFT energies and simulated STM images allowed us to conclude that these species are pyridinium ions located at the catalytically active brim sites. Furthermore, the DFT results for the vibrational modes of the adsorbed pyridinium species agree well with those observed in earlier IR experiments on high surface alumina-supported MoS 2 catalyst. The adsorption sites appear to be very similar to the brim sites involved in hydrogenation reactions in HDS. Thus, the combined STM and DFT results provide new atomic-scale insight into the inhibition effect of basic N-compounds in HDS and the first direct observation of the adsorption mode of basic N-compounds on the catalytically active MoS 2 edges. Our results lend further support to previously reported correlations between inhibiting strength and proton affinity for the N-containing compounds.

Qualitative and quantitative study of nitrogen‐containing compounds in heavy gas oil using comprehensive two‐dimensional gas chromatography with nitrogen phosphorus detection

In this work, a GCxGC-nitrogen-phosphorus detection (NPD) methodology was developed to separate and quantitate nitrogen-containing compounds in Brazilian heavy gas oil. First, the NPD performance was improved in order to achieve best GCxGC performance. The geometry of this detector was also evaluated. The use of an extended jet improved significantly the peak shape. The GCxGC separation was studied using both first and second dimension columns with different internal diameters. The use of a thicker film in both dimensions provided better performance. LODs of 0.16-8.49 pg of individual compounds were achieved. Two different extraction techniques of the neutral and basic nitrogen-containing compounds were also evaluated. The method using ion-exchange resins to separate neutral and basic nitrogen-containing compounds was more efficient than the method using modified silica. As an example, the amounts (microg/g) of each class reported were: indole (2.77), alkyl carbazoles ranging from C(0) to C(6+) (1.467), alkyl benzocarbazoles from C(0) to C(4+) (793), alkyl quinolines (31.2) and alkyl benzoquinolines (21.6) were quantitated.

Preparation and Characterization of a Baicalin-bonded Stationary Phase for High Performance Liquid Chromatograph

The solid–liquid reaction method was used for the preparation of a new High Performance Liquid Chromatography (HPLC) baicalin-bonded stationary phase (BBSP) via amido linkage, by using γ-aminopropyl trimethoxy silane (TM-550) as a coupling reagent and baicalin as a ligand. The structure of the ligand was characterized by Fourier transform infrared spectrum, elemental analysis, thermal analysis and so on. The chromatographic performances of BBSP were preliminarily evaluated, and a related retention mechanism was discussed by using different solutes as probes. Meanwhile, a comparative study between BBSP and conventional octadecyl-bonded stationary phase (ODS) was also carried out under the same conditions. The results showed that the new stationary phase had a relatively weak reversed-phase chromatographic property. Besides hydrophobicity, BBSP could also provide various sites, such as, hydrogen-bonding, π-π, and n-π charge transfer interactions. Synergistic interactions improved the separation selectivity of BBSP for aromatic compounds and their positional isomers when compared with ODS. It could also be observed that the polar amido linkage and hydrophilic glucose residue could minimize the residual silanols effect and improve the separation of basic nitrogen-containing compounds. Additionally, the new packing had strong affinity to flavonoids because of their similar structures. BBSP could be used as an enriching column packing for natural organic flavonoids from medicine herbs.

Effects of Ultrasound Treatment on the Upgradation of Heavy Gas Oil

Catalytic hydrotreating is the most effective process for upgrading heavy gas oil. However, the operating conditions such as high temperatures (633−673 K), high pressures (8.6−8.9 MPa), and consumption of large amounts of catalyst and hydrogen place constraints and limitations on the process. In this investigation the ultrasonic energy is used to treat the heavy gas oil (HGO) without the use of any additives at atmospheric pressure. The lighter gas hydrocarbons given off during the ultrasonic treatment of HGO were identified as methane, ethylene, ethane, and propylene. The basic nitrogen-containing compounds in HGO were more easily cleaved by cavitational energy than that of nonbasic compound. A maximum nitrogen and sulfur conversion of 11% and 7%, respectively, and a 5% reduction in the viscosity were obtained at the optimized sonochemical conditions. A radical chain mechanism is proposed to demonstrate the reactions of hydrocarbons initiated by ultrasound.

Structure characterization of polyaromatic hydrocarbons in Arabian mix vacuum residue by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Molecular formulas of constituents in vacuum residue were characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Evaluation of electrospray ionization (ESI) ability for hydrocarbons by using model compounds indicates that aromatic compounds having more than two fused rings without functional group are detectable as molecular ions, while that basic nitrogen-containing compounds produce protonated ions in the ESI solvent of methanol/chloroform. Thus, even peaks appear for both hydrocarbons and nitrogen-containing compounds in methanol/chloroform. Although basic nitrogen compound detected selectively in mixture of equal molar concentration of hydrocarbons, hydrocarbon could be observed almost the same intensity when the concentration of nitrogen compounds was adjusted as low as that of Arabian mix vacuum residue (AM-VR: N 0.4 wt.%). When ESI solvent of methanol/chloroform/trifluoroacetic acid (TFA) was used, protonated hydrocarbons produced predominantly as odd peaks. Thus, it was revealed that peaks originating from nitrogen-containing compounds and hydrocarbons can be clearly distinguished by changing composition of ESI solvents. In application to AM-VR, protonated nitrogen-containing compounds ([C n H 2 n+ Z N + H] + and [C n H 2 n+ Z NS + H] +; even masses) were observed selectively in methanol/chloroform, and both protonated nitrogen-containing compounds and protonated or sodium-cationized hydrocarbons ([M + H] + or [M + Na] +; odd masses) were observed simultaneously in the solvent composition of methanol/chloroform/TFA.

Speciation of nitrogen-containing compounds in diesel fuel by comprehensive two-dimensional gas chromatography.

Nitrogen-containing compounds in diesel fuel have been speciated by comprehensive two-dimensional gas chromatography with nitrogen chemiluminescence detector (GC x GC-NCD). The speciation of nitrogen-containing compounds in diesel is difficult because of low concentration and complexity. The advantages of GC x GC are improved resolution and enhanced sensitivity. GC x GC-NCD can achieve the type and class separation of nitrogen-containing compounds with an appropriate separation column combination. Diesel contains both neutral (indoles and carbazoles) and basic (pyridines and quinolines) nitrogen-containing compounds. Relative concentrations of each class as well as each carbon number family can be quantified by integrating their peak volumes. This study demonstrates the capability of GC x GC-NCD for speciation of nitrogen-containing compound classes.