Dimensional Gas Chromatography Research Articles

Monoterpanes as molecular indicators to diagnose depositional environments for source rocks of crude oils and condensates

A total of 74 crude oils and condensates originating from various deposits were collected in Tarim, Junggar, Beibuwan and Bohai Bay basins and analyzed by comprehensive two dimensional gas chromatography–time of flight mass spectrometry (GC×GC–TOFMS) in order to investigate the occurrence and distributions of C9 and C10 hydrocarbons. 3-Ethyl-2-methylheptane and 1,1,2,3-tetramethylcyclohexane, two C10 compounds possibly derived from monoterpenoids via cracking and reduction, may be formed under anoxic conditions during diagenesis. We suggest that the ratio of 3-ethyl-2-methylheptane to 3-methylnonane (MT1) coupled with the ratio of 1,1,2,3-tetramethylcyclohexane to propylcyclohexane (MT2), are useful parameters to infer depositional environments and to distinguish oil families. The oils and condensates formed from source rocks deposited under anoxic conditions show high 3-ethyl-2-methylheptane and 1,1,2,3-tetramethylcyclohexane levels (both MT1 and MT2>0.5). Whereas, the hydrocarbons derived from source rocks deposited in oxic conditions contain low amounts of 3-ethyl-2-methylheptane and 1,1,2,3-tetramethylcyclohexane (both MT1 and MT2<0.5). These monoterpane parameters may be useful in petroleum exploration, especially for light oils and condensates where most high molecular weight biomarkers could be cracked or eliminated through fractionation.

Depositional paleoenvironment of Brazilian crude oils from unusual biomarkers revealed using comprehensive two dimensional gas chromatography coupled to time of flight mass spectrometry

Comprehensive two dimensional gas chromatography (GC×GC) coupled to time of flight mass spectrometry (TOFMS), currently one of the most powerful analytical tools that can separate mixtures at a high resolution, was applied to a suite of Brazilian crude oils. The oils were selected based on their different sources, similar maturity levels and little to no biodegradation in the reservoir, in order to study the molecular composition changes for different depositional paleoenvironments. Unusual compounds that are typically at trace levels in petroleum samples were investigated. Besides the usual biomarkers, the technique allowed for the identification of 3β- and 2α-methylhopanes as well as 8,14-seco-hopanes, onocerane isomers, monoaromatic, triaromatic and methyl-triaromatic steroids, benzohopanes and D-ring monoaromatic 8,14-seco-hopanoids. The biomarker parameters that are typically used to predict the organic matter input, paleoenvironmental conditions, thermal maturity and biodegradation of the oils were calculated using the GC×GC-TOFMS data and chemometric techniques were applied. The 3β-methylhopanes and onoceranes were only predominant in the lacustrine oil samples. In contrast, the relative abundance of 2α-methylhopane with an extended side chain was high, and the onocerane levels were low only in the marine oil samples. A new index is proposed based on methylhopanes. The percentage of C31 3β-methylhopane (3βMH31) relative to C30 hopane (H30), 100× (3βMH31/H30) is > 1 for the oils with a lacustrine origin and < 1 for the oils with a marine origin.

Quantitative analysis of fragrance in selectable one dimensional or two dimensional gas chromatography–mass spectrometry with simultaneous detection of multiple detectors in single injection

A selectable one-dimensional (1D) or two-dimensional (2D) gas chromatography–mass spectrometry (GC–MS) system coupled with flame ionization detector (FID) and olfactory detection port (ODP) was employed in this study to analyze perfume oil and fragrance in shower gel. A split/splitless (SSL) injector and a programmable temperature vaporization (PTV) injector are connected via a 2-way splitter of capillary flow technology (CFT) in this selectable 1D/2D GC–MS/FID/ODP system to facilitate liquid sample injections and thermal desorption (TD) for stir bar sorptive extraction (SBSE) technique, respectively. The dual-linked injectors set-up enable the use of two different injector ports (one at a time) in single sequence run without having to relocate the 1D capillary column from one inlet to another. Target analytes were separated in 1D GC–MS/FID/ODP and followed by further separation of co-elution mixture from 1D in 2D GC–MS/FID/ODP in single injection without any instrumental reconfiguration. A 1D/2D quantitative analysis method was developed and validated for its repeatability – tR; calculated linear retention indices (LRI); response ratio in both MS and FID signal, limit of detection (LOD), limit of quantitation (LOQ), as well as linearity over a concentration range. The method was successfully applied in quantitative analysis of perfume solution at different concentration level (RSD≤0.01%, n=5) and shower gel spiked with perfume at different dosages (RSD≤0.04%, n=5) with good recovery (96–103% for SSL injection; 94–107% for stir bar sorptive extraction-thermal desorption (SBSE-TD).

Resolution of co-eluting compounds of Cannabis Sativa in comprehensive two-dimensional gas chromatography/mass spectrometry detection with Multivariate Curve Resolution-Alternating Least Squares

Comprehensive Two Dimensional Gas Chromatography - Mass Spectrometry (GC × GC/qMS) analysis of Cannabis sativa extracts shows a high complexity due to the large variety of terpenes and cannabinoids and to the fact that the complete resolution of the peaks is not straightforwardly achieved. In order to support the resolution of the co-eluted peaks in the sesquiterpene and the cannabinoid chromatographic region the combination of Multivariate Curve Resolution and Alternating Least Squares algorithms was satisfactorily applied. As a result, four co-eluting areas were totally resolved in the sesquiterpene region and one in the cannabinoid region in different samples of Cannabis sativa. The comparison of the mass spectral profiles obtained for each resolved peak with theoretical mass spectra allowed the identification of some of the co-eluted peaks. Finally, the classification of the studied samples was achieved based on the relative concentrations of the resolved peaks.

Chromatographic data analysis. Part 3.3.4: handling hyphenated data in chromatography

This tutorial describes how to analyze three dimensional (3D) pixel-level comprehensive two dimensional (2D) gas chromatography with time of flight mass spectrometry (GC × GC-TOFMS) data. The reader will learn how to baseline-correct and normalize the 3D pixel-level GC × GC-TOFMS chromatograms, how to make an n-way partial least squares (NPLS) model of thirteen 2D pixel-level total ion current (GC × GC-TIC) training set chromatograms, and how to use that NPLS model to predict the biodiesel blend percent composition of 9 independent test set chromatograms.

Correlation of rocket propulsion fuel properties with chemical composition using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry followed by partial least squares regression analysis

There is an increased need to more fully assess and control the composition of kerosene-based rocket propulsion fuels such as RP-1. In particular, it is critical to make better quantitative connections among the following three attributes: fuel performance (thermal stability, sooting propensity, engine specific impulse, etc.), fuel properties (such as flash point, density, kinematic viscosity, net heat of combustion, and hydrogen content), and the chemical composition of a given fuel, i.e., amounts of specific chemical compounds and compound classes present in a fuel as a result of feedstock blending and/or processing. Recent efforts in predicting fuel chemical and physical behavior through modeling put greater emphasis on attaining detailed and accurate fuel properties and fuel composition information. Often, one-dimensional gas chromatography (GC) combined with mass spectrometry (MS) is employed to provide chemical composition information. Building on approaches that used GC–MS, but to glean substantially more chemical information from these complex fuels, we recently studied the use of comprehensive two dimensional (2D) gas chromatography combined with time-of-flight mass spectrometry (GC×GC–TOFMS) using a “reversed column” format: RTX-wax column for the first dimension, and a RTX-1 column for the second dimension. In this report, by applying chemometric data analysis, specifically partial least-squares (PLS) regression analysis, we are able to readily model (and correlate) the chemical compositional information provided by use of GC×GC–TOFMS to RP-1 fuel property information such as density, kinematic viscosity, net heat of combustion, and so on. Furthermore, we readily identified compounds that contribute significantly to measured differences in fuel properties based on results from the PLS models. We anticipate this new chemical analysis strategy will have broad implications for the development of high fidelity composition-property models, leading to an improved approach to fuel formulation and specification for advanced engine cycles.

Fast comprehensive two-dimensional gas chromatography method for fatty acid methyl ester separation and quantification using dual ionic liquid columns

Safflower oil is a complex mixture of C18 saturated and unsaturated fatty acids amongst other fatty acids, and achieving separation between these similar structure components using one dimensional gas chromatography (GC) may be difficult. This investigation aims to obtain improved separation of fatty acid methyl esters in safflower oil, and their quantification using comprehensive two-dimensional GC (GC×GC). Here, GC×GC separation is accomplished by the coupling of two ionic liquid (IL) column phases: the combination of SLB-IL111 with IL59 column phases was finally selected since it provided excellent separation of a FAME standard mixture, as well as fatty acids in safflower and linseed oil, compared to other tested column sets. Safflower oil FAME were well separated in a short run of 16min. FAME validation was demonstrated by method reproducibility, linearity over a range up to 500mgL−1, and limits of detection which ranged from 1.9mgL−1 to 5.2mgL−1 at a split ratio of 20:1. Quantification was carried out using two dilution levels of 200-fold for major components and 20-fold for trace components. The fatty acids C15:0 and C17:0 were not reported previously in safflower oil. The SLB-IL111/IL59 column set proved to be an effective and novel configuration for separation and quantification of vegetable and animal oil fatty acids

Comprehensive Two-dimensional Gas Chromatography with Micro-electron Capture Detector for Analysis of Toxaphene Congeners in Soil

A comprehensive two dimensional gas chromatography coupled with micro-electron capture detector(GC×GC-μECD) method for the simultaneous analysis of 23 congeners of toxaphene in soil has been developed and validated.A DB-XLB column(20 m×0.25 mm×0.25 μm) was chosen as the column for the first dimension,and a BPX-50 column(2 m×0.1 mm×0.1 μm) was chosen as the column for the second dimension.The matrix-matched external standard calibration curves were used for quantitative analysis.The established method showed good linearity with correlation coefficients(r2) higher than 0.99 in the concentration range of 1-200 μg/L.Limits of detection ranged from 0.039 to 0.482μg/L for individual congeners.The relative standard deviations(RSD) of all 23 toxaphene congeners in matrix spiked samples were below 30%(n=5),and recoveries ranged from 55% to 115%.For validation,the developed method was applied to the determination of toxaphene in a soil sample.

Determination of steroids, caffeine and methylparaben in water using solid phase microextraction-comprehensive two dimensional gas chromatography–time of flight mass spectrometry

Analysis of several emerging contaminants (steroids, caffeine and methylparaben) in water using automated solid-phase microextraction with comprehensive two dimensional gas chromatography coupled to time of flight mass spectrometry (SPME-GCxGC–ToF/MS) is presented. Experimental design was used to determine the best SPME extraction conditions and the steroids were not derivatized prior to injection. SPME-GCxGC–ToF/MS provided linear ranges from 0.6 to 1200μgL−1 and limits of detection and quantitation from 0.02 to 100μgL−1. A series of river water samples obtained locally were subjected to analysis. SPME-GCxGC–ToF/MS is readily automated, straightforward and competitive with other methods for low level analysis of emerging contaminants

Assessment of the terpenic profile of Callistemon citrinus (Curtis) Skeels from Mexico

Callistemon species are well known due to its medicinal properties and due to, among others, the relevant health benefits of their terpenic components. This paper aims to in-depth study the terpenic profile of the leaf and flower extracts of Callistemon citrinus with two ages. To fulfill this objective, initially, a screening of the terpenic composition of ethanolic extracts of C. citrinus was performed using GC–MS, and a total of 17 terpenic components were identified in leaf and flower ethanolic extracts. In order to obtain a deeper knowledge, comprehensive two dimensional gas chromatography with time of flight mass spectrometry detection (GC×GC–ToFMS) was also applied, allowing to identify a total of 100 terpenic components in the analyzed ethanolic extracts, from which 77 were identified for the first time in C. citrinus species. A total of 74 and 64 terpenic components were identified in the 4 years old leaf and flower ethanolic extracts, respectively, and 68 and 70 in 20 year old ethanolic extracts, respectively. Moreover, the most abundant terpenic components detected in leaf extracts were 1,8-cineole, α-terpineol, linalool, 4-terpineol, spathulenol, β-gurjunene and viridiflorol, and in flowers were p-cymene, myrtanol, 1,8-cineole, linalool, spathulenol and rosifoliol. Flowers and leaves extracts present a different terpenic profile, with significant differences concerning the type and level of their components, also differences may be noticed related to the extract from 4 and 20 years old. This work allowed achieving a deep characterization of the terpenic composition of leaf and flower C. citrinus, a crucial step in the bioprospection of this plant raw-material as a source of terpenic compounds.

Caracterizaçãodefenóisnobio-óleodapirólisedecaroço de pêssego por GC/MS e GC×GC/TOFMS

In this paper it was analyzed the bio-oil produced by pyrolysis of peach endocarp using 1D-GC/qMS (onedimensional gas chromatography coupled to mass spectrometry) and GC×GC/TOFMS (comprehensive two dimensional gas chromatography coupled to time of flight mass spectrometry). Were tentatively identified 51 compounds by 1D-GC/qMS and 207 compounds by GC×GC/TOFMS. The chemical classes identified in both techniques were alcohols, aldehydes, anhydrides, ketones, esters, ethers and phenols. However, the class of carboxylic acids, hydrocarbons and sugar derivatives were identified only

Planar microfluidic devices in flow modulated comprehensive two dimensional gas chromatography for challenging petrochemical applications

Two three-port planar microfluidic devices are successfully configured for use as a modulator to carry out flow modulated comprehensive two-dimensional gas chromatography. A low thermal mass column module is employed to provide independent temperature control for each separation dimension in the analytical system in some of the applications described. The utility of the analytical system is demonstrated with a number of difficult petrochemical applications comprising analytes that possess a wide range of boiling points; from natural gas to crude oil. A variety of columns with different selectivities and separation mechanisms in the categories of porous layer open tubular and wall-coated open tubular are employed for the applications described.

Wood-derived olefins by steam cracking of hydrodeoxygenated tall oils

Tall oil fractions obtained from Norwegian spruce pulping were hydrodeoxygenated (HDO) at pilot scale using a commercial NiMo hydrotreating catalyst. Comprehensive two dimensional gas chromatography (GC×GC) showed that HDO of both tall oil fatty acids (TOFA) and distilled tall oil (DTO) produced highly paraffinic hydrocarbon liquids. The hydrotreated fractions also contained fatty acid methyl esters and norabietane and norabietatriene isomers. Steam cracking of HDO–TOFA in a pilot plant revealed that high light olefin yields can be obtained, with 35.4wt.% of ethene and 18.2wt.% of propene at a coil outlet pressure (COP) of 1.7bara, a dilution of 0.45kgsteam/kgHDO–TOFA and a coil outlet temperature (COT) of 820°C. A pilot plant coking experiment indicated that cracking of HDO–TOFA at a COT of 850°C results in limited fouling in the reactor. Co-cracking of HDO tall oil fractions with a typical fossil-based naphtha showed improved selectivity to desired light olefins, further demonstrating the potential of large scale olefin production from hydrotreated tall oil fractions in conventional crackers.

Rapid determination of polycyclic aromatic hydrocarbons (PAHs) in tea using two-dimensional gas chromatography coupled with time of flight mass spectrometry

A simple, fast, and cost effective sample preparation procedure has been developed and validated for the determination of 15+1 European Union Polycyclic Aromatic Hydrocarbons (15+1 EU PAHs) in dried tea leave samples. Based on a critical assessment of several sample extraction/clean-up approaches, the method based on the ethyl acetate extraction followed by the use of PAHs dedicated cartridges with molecularly imprinted polymers (MIPs) has been found as an optimal alternative in terms of time demands and obtained good extract purity. For the final identification/quantification of target PAHs, two dimensional gas chromatography coupled to a time-of-flight mass spectrometry (GC×GC–TOFMS) was used. The performance characteristics of the overall analytical method for individual PAHs determined at three spiking levels (0.5, 2.5 and 5μgkg−1) were in following ranges: limits of quantitation (LOQs) 0.05–0.2μgkg−1, repeatabilities 2–9%, and recoveries 73–103%. The recoveries achieved by the newly developed sample preparation procedure when employed for naturally contaminated sample (“incurred” PAHs) were comparable to those obtained by other routinely used approaches employing sonication and/or pressurised liquid extraction for sample analytes isolation. The validated method was subsequently used for the determination of selected genotoxic PAHs in 36 samples of black and green tea obtained from the Czech retail market. The levels of ΣPAH4 (sum of benzo[a]anthracene (BaA), chrysene (CHR), benzo[b]fluoranthene (BbFA) and benzo[a]pyrene (BaP)) in black and green tea leaves ranged from 7.4 to 700μgkg−1 and from 4.5 to 102μgkg−1, respectively. Contamination of tested tea samples by BaP was in the range of 0.2–152μgkg−1.

A one-step method for priority compounds of concern in tar from former industrial sites: Trimethylsilyl derivatisation with comprehensive two-dimensional gas chromatography

A dense non-aqueous phase liquid sample formed by release of coal tar into the environment was derivatised by trimethylsilylation using the reagent N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and extracted in hexane using accelerated solvent extraction. This procedure enables comprehensive extraction of an extensive suite of organic compounds from tar, which has not previously been described. Comprehensive two dimensional gas chromatography coupled to time of flight mass spectrometry (GC×GC–TOFMS) was used for the analysis of the sample for concurrent evaluation of –OH functional group-containing compounds along with aliphatics, polycyclic aromatic hydrocarbons and other typical tar compounds normally determined via classic gas chromatography. Using statistically designed experiments, a range of conditions were tested for complete recovery of four different surrogates. The robustness and repeatability of the optimised derivatisation/extraction method was demonstrated. Finally, more than a hundred and fifty derivatised compounds were identified using mass spectra elucidation and GC×GC logical order of elution.

Characterization of aromatic steroids and hopanoids in marine and lacustrine crude oils using comprehensive two dimensional gas chromatography coupled to time-of-flight mass spectrometry (GCxGC-TOFMS)

The distribution of the aromatic steroids and hopanoids in six crude oils was determined using comprehensive two dimensional gas chromatography time-of-flight mass spectrometry (GCxGC-TOFMS) in order to improve their identification and application in geochemical studies. Co-elution between monoaromatic and triaromatic steroids and benzohopanes and their methylated homologues, which are commonly observed in 1D conventional GC, were resolved, with GCxGC facilitating recognition of the compounds. One important feature was that, despite the oils showing mid-oil window maturity characteristics, the distribution of long chain aromatic steroids decreased in lacustrine samples vs. marine samples. This difference in the distribution of long chain and short chain aromatic steroids may reflect the different origins of these oils although this aspect needs further evaluation.

Qualitative analysis of bio oils of agricultural residues obtained through pyrolysis using comprehensive two dimensional gas chromatography with time-of-flight mass spectrometric detector

The use of bio oil of fast pyrolysis of agricultural and industrial residues may be an economically and environmentally friendly choice for generation of energy and also for the production of chemicals. Suitable applications of rice husk and peach pit are an important issue to avoid improper waste disposal, as Brazilian production of rice and peach reach significant values. The purpose of this work was to perform a detailed qualitative analysis of bio oils of rice husk and peach pit, taking advantage of the higher peak capacity, resolution, sensitivity and selectivity of two-dimensional gas chromatography with mass spectrometric detector (GC×GC/TOFMS). The total number of compounds detected by GC×GC/TOFMS was 503 and 705 for rice husk and peach pit pyrolysates, respectively. Compounds tentatively identified in the same matrices were 106 and 223, respectively. Bio oil compounds were classified in five groups: phenols ketones, acids, ethers, aldehydes, and others. Major classes of both bio oils were phenols and ketones and the major compounds of rice husk and peach pit pyrolysates were guaiacol and furfural, respectively. Twenty compounds (area>1%) of rice husk bio oil and 25 of peach pit oil accounted for 74.04% and 63.62% of the total area, respectively. A structured distribution of compounds of some classes was observed in the two dimensional space, as for example phenols and ketones. Qualitative analysis of these bio oils by GC×GC provided a detailed knowledge of their composition. Both bio oils showed might be employed for the production of chemicals and may be upgraded through an improved pyrolysis process.

Analysis of products from pyrolysis of Brazilian sugar cane straw

The main objective of this work is to investigate the chemical composition of the volatile compounds produced during the pyrolysis of sugar cane straw (SCS). The pyrolysis was conducted in a vertical furnace using a quartz reactor at a temperature of 700°C (7g of SCS, heating rate of 60°C/min, flux of 1mLmin−1 of N2 and 5min of hold time at the final temperature). Pyrolysis products (solid residue and bio-oil) were analyzed. The original biomass and the residual solid phase were characterized by Thermogravimetric Analysis (TGA) and Infrared Spectroscopy (FTIR). The biomass showed a TGA profile similar to cellulose and, according to FTIR analysis, it was rich in oxygenated compounds. The FTIR analysis of solid residue indicated that it was composed mainly by silica. Comprehensive two dimensional gas chromatography with time of flight mass spectrometry detector (GC×GC/TOFMS) was applied in the identification and semi-quantification of main compounds in bio-oil, allowing the identification of 123 compounds, mainly oxygenated (acids, ethers, aldehydes, ketones and phenols) with a predominance of furfural and hexenoic acid. The GC×GC/TOFMS allowed a group type classification of the compounds and a spatial organization that facilitated the identification of the main compounds in the 2D diagram.

Analytical Methods of Levoglucosan, a Tracer for Cellulose in Biomass Burning, by Four Different Techniques

A comparison of analytical approaches for Levoglucosan (<TEX>$C_6H_{10}O_5$</TEX>, commonly formed from the pyrolysis of carbohydrates such as cellulose) and used for a molecular marker in biomass burning is made between the four different analytical systems. 1) Spectrothermography technique as the evaluation of thermograms of carbon using Elemental Carbon & Organic Carbon Analyzer, 2) mass spectrometry technique using Gas Chromatography/mass spectrometer (GC/MS), 3) Aerosol Mass Spectrometer (AMS) for the identification of the particle size distribution and chemical composition, and 4) two dimensional Gas Chromatography with Time of Flight mass spectrometry (GC<TEX>${\times}$</TEX>GC-TOFMS) for defining the signature of Levoglucosan in terms of chemical analytical process. First, a Spectrothermography, which is defined as the graphical representation of the carbon, can be measured as a function of temperature during the thermal separation process and spectrothermographic analysis. GC/MS can detect mass fragment ions of Levoglucosan characterized by its base peak at m/z 60, 73 in mass fragment-grams by methylation and m/z 217, 204 by trimethylsilylderivatives (TMS-derivatives). AMS can be used to analyze the base peak at m/z 60.021, 73.029 in mass fragment-grams with a multiple-peak Gaussian curve fit algorithm. In the analysis of TMS derivatives by GC<TEX>${\times}$</TEX>GC-TOFMS, it can detect m/z 73 as the base ion for the identification of Levoglucosan. It can also observe m/z 217 and 204 with existence of m/z 333. Although the ratios of m/z 217 and m/z 204 to the base ion (m/z 73) in the mass spectrum of GC<TEX>${\times}$</TEX>GC-TOFMS lower than those of GC/MS, Levoglucosan can be separated and characterized from D (-) +Ribose in the mixture of sugar compounds. At last, the environmental significance of Levoglucosan will be discussed with respect to the health effect to offer important opportunities for clinical and potential epidemiological research for reducing incidence of cardiovascular and respiratory diseases.

Stable Carbon Isotope Ratio Analysis of Anhydrosugars in Biomass Burning Aerosol Particles from Source Samples

A new method for stable carbon isotope ratio analysis of anhydrosugars from biomass burning aerosol particle source filter samples was developed by employing Thermal Desorption--2 Dimensional Gas Chromatography--Isotope Ratio Mass Spectrometry (TD-2DGC-IRMS). Compound specific isotopic measurements of levoglucosan, mannosan, and galactosan performed by TD-2DGC-IRMS in a standard mixture show good agreement with isotopic measurements of the bulk anhydrosugars, carried out by Elemental Analyzer--Isotope Ratio Mass Spectrometry (EA-IRMS). The established method was applied to determine the isotope ratios of levoglucosan, mannosan, and galactosan from source samples collected during combustion of hard wood, softwood, and crop residues. δ(13)C values of levoglucosan were found to vary between -25.6 and -22.2‰, being higher in the case of softwood. Mannosan and galactosan were detected only in the softwood samples showing isotope ratios of -23.5‰ (mannosan) and -25.7‰ (galactosan). The isotopic composition of holocellulose in the plant material used for combustion experiments was determined with δ(13)C values between -28.5 and -23.7‰. The difference in δ(13)C of levoglucosan in biomass burning aerosol particles compared to the parent fuel holocellulose was found to be -1.89 (±0.37)‰ for the investigated biomass fuels. Compound specific δ(13)C measurements of anhydrosugars should contribute to an improved source apportionment.