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Exhaled breath volatilomics is a powerful non-invasive tool for biomarker discovery in medical applications, but compound annotation is essential for pathophysiological insights and technology transfer. This study was aimed at investigating the interest of a hybrid approach combining real-time proton transfer reaction-time-of-flight mass spectrometry (PTR-TOF-MS) with comprehensive thermal desorption—two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (TD-GCxGC-TOF-MS) to enhance the analysis and characterization of VOCs in clinical research, using COVID-19 as a use case. VOC biomarker candidates were selected from clinical research using PTR-TOF-MS fingerprinting in patients with COVID-19 and matched to the Human Breathomic Database. Corresponding analytical standards were analysed using both a liquid calibration unit coupled to PTR-TOF-MS and TD-GCxGC-TOF-MS, together with confirmation on new clinical samples with TD-GCxGC-TOF-MS. From 26 potential VOC biomarkers, 23 were successfully detected with PTR-TOF-MS. All VOCs were successfully detected using TD-GCxGC-TOF-MS, providing effective separation of highly chemically related compounds, including isomers, and enabling high-confidence annotation based on two-dimensional chromatographic separation and mass spectra. Four VOCs were identified with a level 1 annotation in the clinical samples. For future applications, the combination of real-time PTR-TOF-MS and comprehensive TD-GCxGC-TOF-MS, at least on a subset of samples from a whole study, would enhance the performance of VOC annotation, offering potential advancements in biomarker discovery for clinical research. [ABSTRACT FROM AUTHOR]

Analyzing fatty acids provides key insights into fat composition for industrial applications and their implications for nutrition and health. Typically, fatty acid analysis involves extracting lipids from the matrix and converting them into fatty acid methyl esters (FAME) through a derivatization process before gas chromatography (GC) analysis. Either one-step or two-step procedures can be found in the literature and as official methods. In this work, different methods exploiting microwave-assisted processes were compared with two official methods from the American Oil Chemical Society (AOCS). Especially, two types of microwave-assisted extractions were employed: solvent extraction and extraction with hydrolysis. The extracts were derivatized using either BF3 or a microwave-assisted methanolic hydrogen chloride solution. These combinations of extraction and derivatization methods were compared also with one-step microwave-assisted extraction and derivatization, and two AOCS reference methods, resulting in seven different methods applied to six different food matrices. The performance of the different procedures was compared based on the FAME profile obtained from the comprehensive two-dimensional GC (GC × GC)-FID analysis.Microwave-assisted processes were shown to be effective, yielding results comparable to the official methods in both the one-step and two-step methods. Moreover, it was shown that the BF3 derivatization could be safely replaced with microwave-assisted derivatization with methanolic hydrogen chloride, providing equivalent performances while enhancing operator safety and environmental friendliness. Some discrepancies in the FAMEs profile were highlighted for the sample of oats, the only explicitly requiring acidic hydrolysis for lipid extraction. Further studies are required to understand the reasons behind these differences and develop a suitable modified method. In conclusion, all the methods were evaluated for greenness and blueness with two specific tools: AGREEprep and BAGI.

Rosa chinensis cultivars with volatile aromas are important resources in the perfume industry. The four rose cultivars introduced to Guizhou province are rich in volatile substances. In this study, volatiles from four Rosa chinensis cultivars were extracted using headspace-solid phase microextraction (HS-SPME), and analyzed with two-dimensional gas chromatography quadrupole time of flight mass spectrometry (GC × GC-QTOFMS). A total of 122 volatiles were identified; the main compounds in these samples were benzyl alcohol, phenylethyl alcohol, citronellol, beta-myrcene and limonene. A total of 68, 78, 71, and 56 volatile compounds were identified in Rosa ‘Blue River’ (RBR), Rosa ‘Crimson Glory’ (RCG), Rosa ‘Pink Panther’ (RPP), and Rosa ‘Funkuhr’ (RF) samples, respectively. The total volatile contents were in the following order: RBR > RCG > RPP > RF. Four cultivars exhibited similar volatility profiles, with alcohols, alkanes, and esters as the major chemical groups, followed by aldehydes, aromatic hydrocarbons, ketones, benzene, and other compounds. Alcohols and aldehydes were quantitatively the two most abundant chemical groups that included the highest number and highest content of compounds. Different cultivars have different aromas, and RCG had high contents of phenyl acetate, rose oxide, trans-rose oxide, phenylethyl alcohol and 1,3,5-trimethoxybenzene, characterized by floral and rose descriptors. RBR contained a high content of phenylethyl alcohol, and RF contained a high content of 3,5-dimethoxytoluene. Hierarchical cluster analysis (HCA) of all volatiles showed that the three cultivars (RCG, RPP, and RF) had similar volatile characteristics and were significantly different from RBR. Differential metabolites among cultivars were screened based on the OPLS-DA model, and there were six main enriched pathways of differential metabolites: biosynthesis of secondary metabolites, monoterpenoid biosynthesis, metabolic pathways, limonene and pinene degradation, sesquiterpenoid and triterpenoid biosynthesis, and alpha-linolenic acid metabolism. The biosynthesis of secondary metabolites is the most differential metabolic pathway. [ABSTRACT FROM AUTHOR]

• GC×GC significantly improved peak resolution and identification of products. • Interaction effects were observed in the co-pyrolysis of PP-PS and HDPE-PS. • New products were detected in the co-pyrolysis of PP-PS. The characterization of pyrolysis products is essential for the development of precise and accurate kinetic models. The resolution of pyrolysis products analyzed using traditional analytical methods may be compromised, resulting in inaccurate product identification and overlapped peaks. This study investigated the product distribution of pyrolysis oil derived from plastics using two analytical techniques: one-dimensional gas chromatography coupled with mass spectrometry (GC–MS) and two-dimensional gas chromatography coupled with flame ionization detector and time-of-flight mass spectrometer (GC×GC–FID/TOF–MS). Pyrolysis experiments of polypropylene (PP), high-density polyethylene (HDPE), polystyrene (PS), as well as co-pyrolysis of PP–PS and HDPE–PS, were conducted at 500 °C using a micropyrolyzer coupled with GC and GC×GC. GC×GC enabled the peak identification 2.8, 5.3, 4.8, 3, and 4.1 times more compared to GC in the pyrolysis of PP, HDPE, PS, PP–PS, and HDPE–PS, respectively. The yield of new chemical classes was found to be 1.3, 5.6, 0.2, 0.8, and 1.5 wt.% for pyrolysis of PP, HDPE, PS, PP–PS, and HDPE–PS, respectively. Furthermore, new products were detected in the co-pyrolysis of PP–PS (1:1), with a total yield of 0.5 ± 0.07 wt.%. Additionally, interaction effects were observed in the co-pyrolysis experiments, such as a 29.7% and 51.3 % increase in the experimental yield of toluene compared to the additive yield for PP–PS and HDPE–PS co-pyrolysis, respectively, which can be attributed to secondary reactions involving the consumption of styrene. [ABSTRACT FROM AUTHOR]

• First study to show the complementarity of GC × GC and LC × SFC for the same sample. • Thorough structural characterisation of depolymerised lignin. • LC × SFC enabled the detection of high molecular mass compounds. • However, GC × GC enabled the detection of small volatile compounds. • Both methods showed a high number of isomers in depolymerised lignin. Two-dimensional gas chromatography (GC × GC) and two-dimensional liquid chromatography (LC × LC) are nowadays widely used in academia and industry due to their high separation power. However, as far as we know, the complementarity of these two techniques has not yet been thoroughly studied based on the analysis of the same sample. Therefore, this was undertaken here by analysing the liquid fraction obtained after depolymerising a natural waste – lignin – with GC × GC and off-line comprehensive LC × SFC (SFC: supercritical fluid chromatography). Using complementary techniques is also important for lignin valorisation, as thorough structural characterisation of the depolymerised product can aid with developing and improving valorisation processes. For the tentative identification, NIST library was used for GC × GC–MS results and MS-DIAL together with SIRIUS for LC × SFC-MS/MS data. This allowed to study which compounds are detectable with the different 2D methods but also to discuss the limitations of the data analysis processes. The previous knowledge that LC techniques are more suitable than GC × GC for the analysis of larger oligomers and other low volatility compounds was confirmed; however, it was seen that GC × GC enabled the analysis of smaller compounds, such as aliphatic alcohols and saturated compounds. Overall, the study demonstrates the complementarity of the two techniques but also draws attention to the different detectable compound groups and classifications that the two techniques can provide. [ABSTRACT FROM AUTHOR]

This work proposes a comprehensive two‐dimensional gas chromatography method for the resolution and quantification of 27 amino acids, including 17 enantiomeric pairs, as stable N‐trifluoroacetyl‐O‐methyl ester derivatives. The derivatization approach in combination with enantioselective two‐dimensional gas chromatography has proven to be highly responsive with a method detection limit of 1–7 pg even for sterically hindered amino acids such as α,α‐dialkylated, and N‐alkylated amino acids. Accurate determination of the enantiomeric excess was achieved with errors in the range of ±0.5%–2.5% (1σ) at concentrations ≥10‒6 M. A thorough study of the mass spectra of the amino acid derivatives allowed the fragmentation pathways to be distinguished, enabling chromatographic peaks to be unambiguously assigned. The proposed method is particularly suited for applications that require the precise determination of enantiomeric excesses such as those concerning the role of d‐amino acid enantiomers in humans, animals, and the environment, as well as for analyses of extraterrestrial samples aimed at understanding the selection of amino acids in stereochemical l‐configuration. [ABSTRACT FROM AUTHOR]

This study investigated the detailed volatile aroma profile of young white wines of Maraština, Vitis Vinifera L., produced by spontaneous fermentation. The wines were produced from 10 vineyards located in two Dalmatian subregions (Northern Dalmatia and Central and Southern Dalmatia). Volatile compounds from the wine samples were isolated by solid-phase extraction (SPE) and analyzed by an untargeted approach using two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC/TOF-MS) and a targeted approach by gas chromatography–tandem mass spectrometry (GC-MS/MS). A comprehensive two-dimensional GC×GC analysis detailed the total volatile metabolites in the wines due to its excellent separation ability. More than 900 compounds were detected after untargeted profiling; 188 of them were identified or tentatively identified. A total of 56 volatile compounds were identified and quantified using GC-MS/MS analysis. The predominant classes in Maraština wines were acids, esters, and alcohols. The key odorants with odor activity values higher than one were β-damascenone, ethyl caprylate, ethyl isovalerate, ethyl 2-methylbutyrate, ethyl caproate, isopentyl acetate, ethyl butyrate, and phenylacetaldehyde. The metabolomics approach can provide a large amount of information and can help to anticipate variation in wines or change winemaking procedures. [ABSTRACT FROM AUTHOR]

To investigate the utility of comprehensive GC×GC gas chromatography metabolomics in finding varietal markers among volatile compounds in non-aromatic red wines, representative samples of the two most important Croatian monovarietal red wines, Plavac mali and Teran, were subjected to analysis by both conventional gas chromatography–mass spectrometry (GC-MS) and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOF-MS) after headspace solid-phase microextraction (HS-SPME). GC-MS was useful for the determination of the basic volatile profile composed mainly of major esters and acids, followed by terpenes and C13-norisoprenoids. GC×GC-TOF-MS allowed the identification of 209 volatiles, among which 49 were significantly different across monovarietal wines. The compounds most characteristic for Teran were two theaspirane isomers, ethyl 3-(methylsulfanyl)propanoate, ethyl methyhexanoate, and ho-trienol, whereas Plavac mali stood out with higher concentrations of tridecane and a 2,3-butanediol isomer. The two monovarietal wines were successfully differentiated between each other by multivariate statistical methods mostly based on GC×GC-TOF-MS data. The presented approach that combines conventional GC-MS and advanced GC×GC-TOF-MS showed a great potential for tracking chemical markers of varietal origin and could be practically applied in managing wine production, quality and typicity, marketing, and protection from forgery. [ABSTRACT FROM AUTHOR]

• Overcoming one-shot limitation of thermal desorption via sample re-collection. • Assessing recollection accuracy and precision. • Recollection and analyzing standards and breath samples using GC×GC-TOFMS. • Compounds' properties, sample moisture, and desorption parameters affect recollection. In this study, we aimed to assess the feasibility of re-collecting breath samples using the Centri® (Markes International, Bridgend, UK) followed by two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) analysis. The work was conducted in two main phases. In the first phase, we evaluated the re-collection performance by analyzing two sets of standards, including a Grob mix primary solution and a standard mixture of 20 selected volatile compounds (VCs) covering different classes of organic species commonly found in breath samples. The intra-day and inter-day precision (reported as relative standard deviation (RSD),%) for the re-collection of the Grob mix primary solution were in the range of 1 % to14 % and 3 % to12 %, respectively. The re-collection accuracy ranged from 78 % to 97 %. The intra-day RSD for the re-collection of the standard mixture of selected VCs was within 20 % for all compounds, except for acetone and nonane. The precision was within 25 % for all compounds, except for nonane, n -hexane, 1,4-dichlorobenzene, and decane, which exhibited less than 36 % RSD. The re-collection accuracy was in the range of 67 % to 129 %. In the second phase of the study, the re-collection performance in breath analysis was evaluated via five repetitive splitting and re-collection of six breath samples obtained from healthy adults, realizing a total of 30 breath analyses. Initially, we evaluated the re-collection performance by considering all features obtained from breath analysis and then focused on the 20 VCs commonly found in breath samples. The re-collection accuracy for total breath features ranged from 86 to 103 %, and the RSDs were in the range of 1.0 % to 10.4 %. For the selected VCs, the re-collection accuracy of all compounds, except for undecane and benzene, was in the range of 71 % to 132 %. [ABSTRACT FROM AUTHOR]

Results of the investigation of polycyclic aromatic hydrocarbons (PAHs) content in fine coal powders prepared according to a special procedure within size classes (-0.2+0.1) mm, (-0.1+0.063) mm, (-0.063+0.04) mm, (-0.04) mm for ten different coal ranks (B, D, G, Zh, K, KS, OS, SS, T, A) from the Kuznetsk coal basin are presented. The qualitative and quantitative PAHs content in coal samples was determined by means of GC-MS using a SCION SQ SELECT instrument (Bruker, USA). The maximal Σ14 PAHs content is observed for A rank coal (224.3 mg/kg), KS (201.9 mg/kg) and T (197.8 mg/ kg), and the minimal Σ14 PAHs content is detected for B rank (2.2 mg/kg) for the size fraction (-0.04) mm. The concentration of benz(a)pyrene, which is a strong carcinogen, is within the range of 0.026‒103.1 mg/kg in coal samples under investigation. At the same time, the fraction of benz(a)pyrene is less than 45% of the total amount of detected PAHs, and it is less stable to the effect of the environment than other PAHs. The most stable component in PAHs series is phenanthrene, which was detected in the series of studied coal samples of different fractions (0.061‒43.7 mg/kg). Phenanthrene may be considered a PAHs of priority, and it may be used as a reference compound to evaluate the influence of coal mining and processing on the environment. The group composition of hydrocarbons in coal extracts was determined by means of two-dimensional gas chromatography with flame ionization detection.

A monolith based on foamed graphite is used for the sorption of hydrocarbons (alkanes, cycloalkanes, arenes) as markers of oil pollution. This material is patented by chemical engineers from the Department of Chemistry of the Moscow State University. It is shown that absorbed compounds can be determined qualitatively and quantitatively by GC/GC/MS with a thermal desorption system. [ABSTRACT FROM AUTHOR]

Results of the investigation of polycyclic aromatic hydrocarbons (PAHs) content in fine coal powders prepared according to a special procedure within size classes (-0.2+0.1) mm, (-0.1+0.063) mm, (-0.063+0.04) mm, (-0.04) mm for ten different coal ranks (B, D, G, Zh, K, KS, OS, SS, T, A) from the Kuznetsk coal basin are presented. The qualitative and quantitative PAHs content in coal samples was determined by means of GC-MS using a SCION SQ SELECT instrument (Bruker, USA). The maximal ∑14 PAHs content is observed for A rank coal (224.3 mg/kg), KS (201.9 mg/kg) and T (197.8 mg/kg), and the minimal ∑14 PAHs content is detected for B rank (2.2 mg/kg) for the size fraction (-0.04) mm. The concentration of benz(a)pyrene, which is a strong carcinogen, is within the range of 0.026-103.1 mg/kg in coal samples under investigation. At the same time, the fraction of benz(a)pyrene is less than 45% of the total amount of detected PAHs, and it is less stable to the effect of the environment than other PAHs. The most stable component in PAHs series is phenanthrene, which was detected in the series of studied coal samples of different fractions (0.061-43.7 mg/kg). Phenanthrene may be considered a PAHs of priority, and it may be used as a reference compound to evaluate the influence of coal mining and processing on the environment. The group composition of hydrocarbons in coal extracts was determined by means of two-dimensional gas chromatography with flame ionization detection. [ABSTRACT FROM AUTHOR]

Coffee, one of the most popular beverages in the world, attracts consumers by its rich aroma and the stimulating effect of caffeine. Increasing consumers prefer decaffeinated coffee to regular coffee due to health concerns. There are some main decaffeination methods commonly used by commercial coffee producers for decades. However, a certain amount of the aroma precursors can be removed together with caffeine, which could cause a thin taste of decaffeinated coffee. To understand the difference between regular and decaffeinated coffee from the volatile composition point of view, headspace solid-phase microextraction two-dimensional gas chromatography time-of-flight mass spectrometry (HS-SPME-GC×GC-TOFMS) was employed to examine the headspace volatiles of eight pairs of regular and decaffeinated coffees in this study. Using the key aroma-related volatiles, decaffeinated coffee was significantly separated from regular coffee by principal component analysis (PCA). Using feature-selection tools (univariate analysis: t-test and multivariate analysis: partial least squares-discriminant analysis (PLS-DA)), a group of pyrazines was observed to be significantly different between regular coffee and decaffeinated coffee. Pyrazines were more enriched in the regular coffee, which was due to the reduction of sucrose during the decaffeination process. The reduction of pyrazines led to a lack of nutty, roasted, chocolate, earthy, and musty aroma in the decaffeinated coffee. For the non-targeted analysis, the random forest (RF) classification algorithm was used to select the most important features that could enable a distinct classification between the two coffee types. In total, 20 discriminatory features were identified. The results suggested that pyrazine-derived compounds were a strong marker for the regular coffee group whereas furan-derived compounds were a strong marker for the decaffeinated coffee samples. [ABSTRACT FROM AUTHOR]

This study investigated the detailed volatile aroma profile of young white wines of Maraština, Vitis Vinifera L., produced by spontaneous fermentation. The wines were produced from 10 vineyards located in two Dalmatian subregions (Northern Dalmatia and Central and Southern Dalmatia). Volatile compounds from the wine samples were isolated by solid-phase extraction (SPE) and analyzed by an untargeted approach using two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC/TOF-MS) and a targeted approach by gas chromatography–tandem mass spectrometry (GC-MS/MS). A comprehensive two-dimensional GC×GC analysis detailed the total volatile metabolites in the wines due to its excellent separation ability. More than 900 compounds were detected after untargeted profiling; 188 of them were identified or tentatively identified. A total of 56 volatile compounds were identified and quantified using GC-MS/MS analysis. The predominant classes in Maraština wines were acids, esters, and alcohols. The key odorants with odor activity values higher than one were β-damascenone, ethyl caprylate, ethyl isovalerate, ethyl 2-methylbutyrate, ethyl caproate, isopentyl acetate, ethyl butyrate, and phenylacetaldehyde. The metabolomics approach can provide a large amount of information and can help to anticipate variation in wines or change winemaking procedures.

Carbohydrates, in particular the d -enantiomers of ribose, 2-deoxyribose, and glucose, are essential to life's informational biopolymers (RNA/DNA) and for supplying energy to living cells through glycolysis. Considered to be potential biosignatures in the search of past or present life, our capacity to detect and quantify these essential sugars is crucial for future space missions to the Moon, Mars or Titan as well as for sample-return missions. However, the enantioselective analysis of carbohydrates is challenging and both research and routine applications, are lacking efficient methods that combine highly sensitive and reproducible detection with baseline enantioselective resolution and reliable enantiomeric excess (ee) measurements. Here, we present four different derivatization strategies in combination with multidimensional gas chromatography coupled to a reflectron time-of-flight mass spectrometer (GC×GC–TOF-MS) for the enantioselective resolution of C3 to C6 carbohydrates potentially suitable for sample-return analyses. Full mass spectral interpretation and calibration curves for one single-step (cyclic boronate derivatives) and three two-step derivatization protocols (aldononitrile−acetate, hemiacetalization−trifluoroacetylation, and hemiacetalization−permethylation) are presented for concentrations ranging from 1 to 50 pmol μL⁻1 with correlation coefficients R 2 > 0.94. We compared several analytical parameters including reproducibility, sensitivity (LOD and LOQ), overall separation, chiral resolution (R S), mass spectrum selectivity, stability during long term storage, and reliability of ee measurements to guide the application-dependent selection of optimal separation and quantification performance. [Display omitted] • Analytical workflow combining derivatization with enantio-GC×GC for C3–C6 sugars. • Simultaneous GC×GC enantioresolution of C3–C6 sugars. • Optimized method detection limits below 50 pmol. • Reliable determination of small enantiomeric excesses in trace amounts. [ABSTRACT FROM AUTHOR]

To investigate the utility of comprehensive GC×GC gas chromatography metabolomics in finding varietal markers among volatile compounds in non-aromatic red wines, representative samples of the two most important Croatian monovarietal red wines, Plavac mali and Teran, were subjected to analysis by both conventional gas chromatography–mass spectrometry (GC-MS) and comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOF-MS) after headspace solid-phase microextraction (HS-SPME). GC-MS was useful for the determination of the basic volatile profile composed mainly of major esters and acids, followed by terpenes and C13-norisoprenoids. GC×GC-TOF-MS allowed the identification of 209 volatiles, among which 49 were significantly different across monovarietal wines. The compounds most characteristic for Teran were two theaspirane isomers, ethyl 3-(methylsulfanyl)propanoate, ethyl methyhexanoate, and ho-trienol, whereas Plavac mali stood out with higher concentrations of tridecane and a 2,3-butanediol isomer. The two monovarietal wines were successfully differentiated between each other by multivariate statistical methods mostly based on GC×GC-TOF-MS data. The presented approach that combines conventional GC-MS and advanced GC×GC-TOF-MS showed a great potential for tracking chemical markers of varietal origin and could be practically applied in managing wine production, quality and typicity, marketing, and protection from forgery.

Coffee, one of the most popular beverages in the world, attracts consumers by its rich aroma and the stimulating effect of caffeine. Increasing consumers prefer decaffeinated coffee to regular coffee due to health concerns. There are some main decaffeination methods commonly used by commercial coffee producers for decades. However, a certain amount of the aroma precursors can be removed together with caffeine, which could cause a thin taste of decaffeinated coffee. To understand the difference between regular and decaffeinated coffee from the volatile composition point of view, headspace solid-phase microextraction two-dimensional gas chromatography time-of-flight mass spectrometry (HS-SPME-GC×GC-TOFMS) was employed to examine the headspace volatiles of eight pairs of regular and decaffeinated coffees in this study. Using the key aroma-related volatiles, decaffeinated coffee was significantly separated from regular coffee by principal component analysis (PCA). Using feature-selection tools (univariate analysis: t-test and multivariate analysis: partial least squares-discriminant analysis (PLS-DA)), a group of pyrazines was observed to be significantly different between regular coffee and decaffeinated coffee. Pyrazines were more enriched in the regular coffee, which was due to the reduction of sucrose during the decaffeination process. The reduction of pyrazines led to a lack of nutty, roasted, chocolate, earthy, and musty aroma in the decaffeinated coffee. For the non-targeted analysis, the random forest (RF) classification algorithm was used to select the most important features that could enable a distinct classification between the two coffee types. In total, 20 discriminatory features were identified. The results suggested that pyrazine-derived compounds were a strong marker for the regular coffee group whereas furan-derived compounds were a strong marker for the decaffeinated coffee samples.

The liquid fraction of tire pyrolysis products was comprehensively analyzed by gas chromatography–mass spectrometry and two-dimensional gas chromatography. The direct (nonpolar–polar) и and inverse (polar–nonpolar) column combinations were used. The inverse combination allows efficient separation of alkanes and alkenes. Aliphatic hydrocarbons constitute no more than 24 wt % of the liquid fraction, with the remainder being aromatic, mainly monoaromatic, compounds. The sulfur content of the liquid fraction is about 0.7 wt %; sulfur is mainly present in the form of thiophene derivatives. [ABSTRACT FROM AUTHOR]

A method for determination of oxygenates and benzene in gasoline was established using two-column switching-back flushing two-dimensional gas chromatography technique. By optimizing the chromatographic valve Switching time and chromatographic conditions, the analyses were cut from precolumn to separation column. The results show that the detect ion range of oxide and benzene is 0.10%-20. 00% and 0.05% -2.50% respectively, recovery rate is 96.4% -102. 3%, and the relative standard deviation (RSD) of the method is less than 1.14 % . The method has good reproducibility and the detection results are accurate and reliable. [ABSTRACT FROM AUTHOR]

Highlights • Both new orthogonality metrics %BIN and %FIT are easy to obtain. • Both metrics do not require any settings to calculate orthogonality. • Both metrics show high correlation with experts' orthogonality scores. • Both metrics improve the concurrence of expert's orthogonality grading. Abstract Orthogonality can be used as a selection parameter for two-dimensional chromatography column selection (e.g. in GC × GC or LC × LC) or for method optimization purposes, both aiming for maximal orthogonality for a particular analytical application. In order to improve the concurrence of two-dimensional chromatography expert's orthogonality grading, two orthogonality metrics, %FIT and %BIN, were developed, evaluated and compared with the Asterisks orthogonality metric. The %BIN is a bin counting approach where the number of bins is fixed at 25 and deviations from the expected average number of peaks per bin is used as the basis for the orthogonality calculation. The %FIT is based on fitting polynomials of degree two, through the xy and the yx data and calculating the average minimal distance and standard deviation of all data points above and below the fitted polynomials. The orthogonality metrics were evaluated by using 14 different types of computer generated xy datasets and two measured LC × LC datasets. Both %FIT and %BIN, were shown to have a larger discriminative power than the Asterisks equations, and are in good agreement with the orthogonality scores for 2D-chromatograms provided by nine experts. [ABSTRACT FROM AUTHOR]

Abstract Due to possible matrix interferences and artefact generation during sample preparation, careful method validation is required for quantitative bioanalytical methods, especially for analytes that are only present in low concentrations. Using the identification and quantification of progesterone metabolites in the urine of newborns as an example, we show how modern high-resolution instruments can be used to verify analyte assignment and avoid pitfalls commonly encountered by the use of low-resolution instruments. [ABSTRACT FROM AUTHOR]

This work systematically assessed the effects of pyrolysis parameters, such as sample weight, particle size, carrier gas flow rate, and temperature, on product speciation and distribution in the pyrolysis of polypropylene (PP) for intrinsic kinetics. This study employed a Box-Behnken design (BBD), along with the analysis of BBD boundary conditions, as well as conditions beyond the BBD to validate the pyrolysis conditions in the primary decomposition of PP using a micropyrolyzer coupled to two-dimensional chromatography with flame ionization and time-of-flight spectrometer detectors (Py–GC × GC–FID/TOF–MS). Statistical differences and similarities in the product distribution of the experiments were determined using principal component analysis (PCA). Characteristic time analysis indicated that the sample weights employed in the study were within the isothermal kinetically controlled region, with film thickness ranging from 4.85 to 14.46 µm. The analysis of 600 pyrolysis products identified and quantified in the pyrolysis of PP for the condition combinations evaluated in BBD resulted in statistical differences at temperatures of 460, 530, and 600 oC, with C 3 to C 35 yields ranging from 39.88 ± 2.08 to 66.61 ± 3.26 wt%. However, no statistical differences were found in the pyrolysis product distribution within the ranges of sample weight (50 – 150 µg), particle size (53 – 125, 125 – 300, and >300 µm), and carrier gas flow rate (100 – 300 ml min-1) studied in the BBD experimental space. The analysis of the border conditions showed that a combination of the lowest carrier gas flow rate (100 ml min-1) and the highest sample weight (150 μ g) resulted in statistically different product distribution at the studied pyrolysis temperatures compared to the combination suggested by BBD. Conditions beyond the BBD, including a sample weight of 800 µg and a carrier gas flow rate of 30 ml min-1, resulted in statistically different product distributions compared to the BBD. Notably, new products such as polycyclic aromatic hydrocarbons (PAHs) were identified. The findings from this work clearly show the importance of selecting appropriate pyrolysis parameters to obtain kinetically relevant experimental data, which in turn serves as a valuable guide for the development and validation of (micro-) kinetic models. • Identified pyrolysis parameter ranges for PP intrinsic kinetics. • GC×GC with PCA verified experimental conditions for intrinsic kinetics. • GC×GC analysis enabled separation of aromatics indicative of secondary reactions. [ABSTRACT FROM AUTHOR]

To differentiate white wines from Croatian indigenous varieties, volatile aroma compounds were isolated by headspace solid-phase microextraction (HS-SPME) and analyzed by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOF-MS) and conventional one-dimensional GC-MS. The data obtained were subjected to uni- and multivariate statistical analysis. The extra separation ability of the GC×GC second dimension provided additional in-depth volatile profile information, with more than 1000 compounds detected, while 350 were identified or tentatively identified in total by both techniques, which allowed highly efficient differentiation. A hundred and sixty one compounds in total were significantly different across monovarietal wines. Monoterpenic compounds, especially α-terpineol, followed by limonene and linalool, emerged as the most powerful differentiators, although particular compounds from other chemical classes were also shown to have notable discriminating ability. In general, Škrlet wine was the most abundant in monoterpenes, Malvazija istarska was dominant in terms of fermentation esters concentration, Pošip contained the highest levels of particular C13-norisoprenoids, benzenoids, acetates, and sulfur containing compounds, Kraljevina was characterized by the highest concentration of a tentatively identified terpene γ-dehydro-ar-himachalene, while Maraština wine did not have specific unambiguous markers. The presented approach could be practically applied to improve defining, understanding, managing, and marketing varietal typicity of monovarietal wines.

Traditional Chinese medicines (TCMs) possess a rich historical background, unique theoretical framework, remarkable therapeutic efficacy, and abundant resources. However, the modernization and internationalization of TCMs have faced significant obstacles due to their diverse ingredients and unknown mechanisms. To gain deeper insights into the phytochemicals and ensure the quality control of TCMs, there is an urgent need to enhance analytical techniques. Currently, two-dimensional (2D) chromatography, which incorporates two independent separation mechanisms, demonstrates superior separation capabilities compared to the traditional one-dimensional (1D) separation system when analyzing TCMs samples. Over the past decade, new techniques have been continuously developed to gain actionable insights from complex samples. This review presents the recent advancements in the application of multidimensional chromatography for the quality evaluation of TCMs, encompassing 2D-gas chromatography (GC), 2D-liquid chromatography (LC), as well as emerging three-dimensional (3D)-GC, 3D-LC, and their associated data-processing approaches. These studies highlight the promising potential of multidimensional chromatographic separation for future phytochemical analysis. Nevertheless, the increased separation capability has resulted in higher-order data sets and greater demands for data-processing tools. Considering that multidimensional chromatography is still a relatively nascent research field, further hardware enhancements and the implementation of chemometric methods are necessary to foster its robust development., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 Tianjin Press of Chinese Herbal Medicines. Published by ELSEVIER B.V.)

Graphical abstract Highlights • Two-year-old char-fortified on-site sewage treatment facilities were studied. • Contaminants were identified by GC × GC-ToF-MS, GC-ToF-MS and LC-IM-QToF-MS. • The comprehensive screening resulted in 74 identified emerging organic contaminants. • Biochar fortification increased the removal of several studied contaminants. • Removal was likely due to sorption and biodegradation. Abstract To remove organic contaminants from wastewater using cost-efficient and currently existing methods, our study investigated char-fortified filter beds for on-site sewage treatment facilities (OSSFs) in a long-term field setting. OSSFs are commonly used in rural and semi-urban areas worldwide to treat wastewater when municipal wastewater treatment is not economically feasible. First, we screened for organic contaminants with gas chromatography and liquid chromatography mass spectrometry-based targeted and untargeted analysis and then we developed quantitative structure-property relationship models to search for key molecular features responsible for the removal of organic contaminants. We identified 74 compounds (24 confirmed by reference standards) including plasticizers, UV stabilizers, fragrances, pesticides, surfactant and polymer impurities, pharmaceuticals and their metabolites, and many biogenic compounds. Sand filters that are used as a secondary step after the septic tank in OSSFs could remove hydrophobic contaminants. The addition of biochar significantly increased the removal of these and a few hydrophilic compounds (Wilcoxon signed-rank test, α = 0.05). Besides hydrophobicity-driven sorption, biodegradation was suggested to be the most important removal pathway in this long-term field application. However, further improvements are necessary to remove very hydrophilic contaminants as they were not removed with sand and biochar-fortified sand. [ABSTRACT FROM AUTHOR]

The development of instrumental analytical techniques provided the opportunity for in-depth characterization of many food matrices. In particular, the use of gas chromatography coupled with mass spectrometry gives impressive results in terms of quality and authenticity testing, conducting food freshness evaluations and contamination assessments. A new variant of gas chromatography, namely two-dimensional gas chromatography (GC × GC), and various versions of mass spectrometry have been developed since last 15 years, and they still remain at the time of their renaissance. The present critical review is focused on the use of GC × GC coupled with mass spectrometry for qualitative and quantitative reasons in food analysis. It is explained how powerful analytical tool is above-mentioned technical solution. Special attention is devoted to the issues related to the development of this technique during last years in terms of key construction elements, such as modulators and MS detectors. Finally, the critical discussion on many various aspects including advantages and more important disadvantages, caused probable moderate interest of this solution, in food analytics is concerned. [ABSTRACT FROM AUTHOR]

Energy storage via liquid organic hydrogen carrier (LOHC) systems has gained significant attention in recent times. A dibenzyltoluene (DBT) based LOHC offers excellent properties which largely solve today's hydrogen storage challenges. Understanding the course of the dehydrogenation reaction is important for catalyst and process optimization. Therefore, reliable and exact methods to determine the degree of hydrogenation (doh) are important. We here present other possible techniques, namely: comprehensive two-dimensional gas chromatography coupled with time of flight mass spectrometry (2D-GC-TOF-MS) and single quadrupole-mass spectrometry gas chromatogram system (GC-SQ-MS). The 2D-GC-TOF-MS results indicate that isomer fractions lose three molecules of hydrogen, as follows: H18-DBT, H12-DBT, H6-DBT and H0-DBT, and the doh decreases with an increase in dehydrogenation temperature. 1 H NMR and GC-SQ-MS were employed as additional analytical techniques. The GC-SQ-MS was also used to analyse decomposition products that result from thermal cracking of reaction mixture molecules. [ABSTRACT FROM AUTHOR]

The coupling of comprehensive two-dimensional gas chromatography with high-resolution time-of-flight mass spectrometry offers the best separation efficiency combined with accurate mass measurements over a wide mass range. The tremendous power of this screening tool is illustrated by trace qualitative screening analysis of organohalogenated compounds (OHCs) in pet cat hair. Tentative identification was supported by mass spectral database searches and elemental formula prediction from the experimentally determined accurate mass data. This screening approach resulted in the first tentative identification of pentabromoethylbenzene, decabromodiphenyl ethane, hexabromocyclododecane, trisbromoneopentyl alcohol, tris(2-chloroethyl) phosphate and tris(2-chloroisopropyl)phosphate in the South African indoor environment. A total of seventy-two OHCs were identified in the samples and include known flame retardants, such as polybrominated diphenyl ethers, and legacy contaminants such as polychlorinated biphenyls and organochlorine, organophosphorous and pyrethroid pesticides. The results obtained from cat hair indicate that these pets are exposed to complex mixtures of OHCs and the detection of these compounds suggests that non-invasive cat hair samples can be used to model indoor exposure with reference to external deposition of OHCs present in the air and dust surrounding people. Toddlers share the same environment as pet cats and therefore also the same health risks. [ABSTRACT FROM AUTHOR]

Salmonella Typhi is the causative agent of typhoid. Typhoid is diagnosed by blood culture, a method that lacks sensitivity, portability and speed. We have previously shown that specific metabolomic profiles can be detected in the blood of typhoid patients from Nepal (Näsström et al., 2014). Here, we performed mass spectrometry on plasma from Bangladeshi and Senegalese patients with culture confirmed typhoid fever, clinically suspected typhoid, and other febrile diseases including malaria. After applying supervised pattern recognition modelling, we could significantly distinguish metabolite profiles in plasma from the culture confirmed typhoid patients. After comparing the direction of change and degree of multivariate significance, we identified 24 metabolites that were consistently up- or down regulated in a further Bangladeshi/Senegalese validation cohort, and the Nepali cohort from our previous work. We have identified and validated a metabolite panel that can distinguish typhoid from other febrile diseases, providing a new approach for typhoid diagnostics.

The Halahatang Oilfield in the Tabei Uplift of the Tarim Basin has substantial petroleum potential and contains many prolific commercial oil reservoirs. In this study, a total of 15 DST oils were sampled from the northern Halahatang oilfield, and their geochemistry of C 5 –C 13 light hydrocarbons (LHs) is characterized by two-dimensional gas chromatography (GC × GC). The concentrated clusters in the LH triangular diagrams and parent-daughter plots of the n -Heptane (%C 7 ) vs. ln (Cps/CHs) corroborating with the similar K 1 values (1.01–1.23), imply a high degree of compositional similarity and source affinity. The C 7 LHs show a predominance of n -heptane (30.07%–42.75%) and a nearly identical abundance of MCyC 6 (35.92%–45.85%), low I MCyC6 (methylcyclohexane index) value (35.92%–45.57%) and a moderate I CH (cyclohexane index) value (25.92%–45.66%), demonstrating that they were typical marine oils mainly originated from a substantial amount of sapropelic organic matter mixed with a nearly equivalent amount of humic one. The LH maturity indexes, such as the heptane (H) ratio (17.80%–29.28%), isoheptane (I) ratio (1.25–2.15), °C temp (113.72 °C −124.63 °C),methyladmantane index (MAI: 52.15%–63.65%) and equivalent vitrinite reflectance (1.1%–1.3% R o) indicate a high thermal maturity. The values of 3-ethyl-2-methylheptane to 3-methylnonane (MT 1 : 0.91–3.65), 1,1,2,3-tetramethylcyclohexane to propylcyclohexane (MT 2 : 0.85–1.37), 2-methyl-3-ethylheptane/2,6-dimethyloctane (MTR: 0.59–1.25), and Pr/Ph (0.87–1.62) observed for the northern Halahatang oils consistently suggest a marine carbonate lithology for the source rock deposited in an anoxic, reducing environment. Geochemical and geological correlation imply the Halahatang oils are possibly derived from the O 2+3 potential source rocks. [ABSTRACT FROM AUTHOR]

In this research two-dimensional GC was used to analyse, for the first time, the detailed fatty acid (FA) profiles of 11 dairy matrices: raw milk (evening whole, evening partially skimmed, morning whole, and vat milk), cream, fresh cheese, whey, ricotta, scotta, 6- and 12-month-ripened cheeses, obtained across artisanal cheese- and ricotta-making trials carried out during the summer period while cows were on highland pastures. Samples were collected during 7 cheese- and ricotta-making procedures carried out at 2-week intervals from bulk milk to study possible differences in the transfer and modification of FA. Compared with morning milk, evening milk had fewer de novo synthetised FA. The detailed FA profile of partially skimmed milk differed little from that of evening whole milk before skimming, but the cream obtained differed from partially skimmed milk and from fresh cheese in about half the FA, due mainly to higher contents of all de novo FA, and lower contents of n-3 and n-6 FA. Fresh cheese and whey had similar FA profiles. The ricotta manufacturing process affected the partition of FA between ricotta and scotta, the FA profile of the latter differing in terms of groups and individual FA from the former, whereas ricotta and fresh cheese had similar composition of FA. In general, there was an increase in medium-chain saturated FA, and a decrease in many polyunsaturated FA during the first 6 months of ripening, but not during the second 6 months. Two-dimensional GC yielded a very detailed and informative FA profile on all the 11 dairy products and by-products analysed. [ABSTRACT FROM PUBLISHER]

A pixel-by-pixel method for correcting retention time (RT) shifts in whole chromatograms from comprehensive two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry (GC × GC-HRTOFMS) is introduced. A previously developed robust algorithm for correcting RT shifts was extended to high-resolution mass-spectral data. The performance of the new method in terms of decreasing RT shifts and peak volume changes was tested on GC × GC-HRTOFMS data. The RT shift correction algorithm, using linear interpolation for the 1st dimension and Sibson natural neighbor interpolation for the 2nd dimension, performed well for systematically shifted data acquired using two different temperature programs in terms of decreasing RT differences and alterations to the peak volumes and mass spectra. A modified RT shift correction algorithm, using Sibson natural neighbor for both dimensions, performed better for RT shifts caused by column damage, for which the original interpolation method did not appropriately correct RT shifts. Although further investigation would be required for more types of severe shifts, this study shows that the developed method is useful for correcting RT shifts with GC × GC-HRTOFMS. [ABSTRACT FROM AUTHOR]

This study is to develop a GC × GC method with electron capture detection (ECD) to analyze atmospheric halocarbons in the concentration range of parts per trillion by volume (pptv). To enrich atmospheric halocarbons a home-built thermal desorption (TD) device was coupled to the GC × GC-ECD. The technique of flow modulation was adopted using a Deans switch for GC × GC. Several column combinations of first and second dimensions were tested and the column set of DB–5 × TG-1301 was found to show the best orthogonality for halocarbons. A series of modulation parameters were tested for their optimal settings. The modulation period (P M ) was found to have minimal wrap-around when set at 3 s. The modulation ratio (M R ) was determined to be 7.82 to ensure reproducible results and maximum sensitivity. The modulation duty cycle (DC) was calculated to be approximately 0.17. Nine halocarbons were separated successfully and seven were calibrated with the use of a certified standard gas mixture. The correlation coefficients (R 2 ) were greater than 0.9972. The reproducibility was better than 1.90% as expressed in relative standard deviation (RSD; N = 30) and the detection limits were in the range of pptv for the target halocarbons. A field test by continuous analyzing ambient air with hourly resolution was performed to show the stability of the method as suggested by the homogeneity of certain halocarbons, while also reflecting concentration variation for others when emissions did arise. [ABSTRACT FROM AUTHOR]

Eleven Brazilian oil samples from different sources, biodegradation and maturity levels were analyzed by comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-TOFMS). Geochemical characterization associated with principal component analysis (PCA) allowed the identification of the three most mature oils. The GC×GC chromatographic conditions used in this study allowed us to perform group-type (or chemical class) separation in the following second dimension ( 2 D) order: (i) tricyclic terpanes; followed by (ii) steranes with 3 rings containing 6 carbon atoms and 1 ring containing 5 carbon atoms; (iii) tetracyclic terpanes with 4 rings containing 6 carbon atoms; (iv) pentacyclic terpanes with 4 rings containing 6 carbon atoms and 1 ring containing 5 carbon atoms; and finally (v) pentacyclic terpanes with 5 rings containing 6 carbon atoms. This information was used to tentatively identify the ring structure of eight unusual compounds found in the saturated fraction of the oils. These compounds had the double bond equivalent (DBE) value four, which was calculated based on molecular ions M + at m / z 274, 288 and 316, indicating possible tetracyclic structures. Two of them presented a diagnostic peak at m / z 191 and six at m / z 203. A trend between the ratios of two of these unusual compounds and the C 24 tetracyclic terpane versus 4,6/1,4 dimethyldibenzothiophene ratio shows promise as a maturation parameter. Thus, these unusual compounds are prone to respond to the maturation on a scale from mature to overmature, when compared with traditional maturation parameters. [ABSTRACT FROM AUTHOR]

Analysis of seven pesticides in sediments was successfully achieved using comprehensive two-dimensional gas chromatography with micro-electron capture detection, as it provided higher sensitivity and less matrix interference. Repeatability and intermediate precision of peak areas and heights were less than 4% and the recovery percentage for the analytes ranged from 52 to 115%. Instrumental LOD and LOQ were in the range of 0.60 to 2.31 μg L-1 and 1.83 to 5.62 μg L-1, respectively. Concentrations of 3.34 μg kg-1 (dry basis) for trifloxystrobin and azoxystrobin (below the LOQ) were found in a sediment sample.

Rosa chinensis cultivars with volatile aromas are important resources in the perfume industry. The four rose cultivars introduced to Guizhou province are rich in volatile substances. In this study, volatiles from four Rosa chinensis cultivars were extracted using headspace-solid phase microextraction (HS-SPME), and analyzed with two-dimensional gas chromatography quadrupole time of flight mass spectrometry (GC × GC-QTOFMS). A total of 122 volatiles were identified; the main compounds in these samples were benzyl alcohol, phenylethyl alcohol, citronellol, beta-myrcene and limonene. A total of 68, 78, 71, and 56 volatile compounds were identified in Rosa 'Blue River' (RBR), Rosa 'Crimson Glory' (RCG), Rosa 'Pink Panther' (RPP), and Rosa 'Funkuhr' (RF) samples, respectively. The total volatile contents were in the following order: RBR > RCG > RPP > RF. Four cultivars exhibited similar volatility profiles, with alcohols, alkanes, and esters as the major chemical groups, followed by aldehydes, aromatic hydrocarbons, ketones, benzene, and other compounds. Alcohols and aldehydes were quantitatively the two most abundant chemical groups that included the highest number and highest content of compounds. Different cultivars have different aromas, and RCG had high contents of phenyl acetate, rose oxide, trans-rose oxide, phenylethyl alcohol and 1,3,5-trimethoxybenzene, characterized by floral and rose descriptors. RBR contained a high content of phenylethyl alcohol, and RF contained a high content of 3,5-dimethoxytoluene. Hierarchical cluster analysis (HCA) of all volatiles showed that the three cultivars (RCG, RPP, and RF) had similar volatile characteristics and were significantly different from RBR. Differential metabolites among cultivars were screened based on the OPLS-DA model, and there were six main enriched pathways of differential metabolites: biosynthesis of secondary metabolites, monoterpenoid biosynthesis, metabolic pathways, limonene and pinene degradation, sesquiterpenoid and triterpenoid biosynthesis, and alpha-linolenic acid metabolism. The biosynthesis of secondary metabolites is the most differential metabolic pathway., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Quan, Jin, Qian, Li and Zhou.)

In this scientific contribution we verified the qualitative and quantitative validity of the DIN EN 12916 or ASTM D6591 based on high performance liquid chromatography with a refractive index detector (HPLC – RID) for the correct determination of aromatic compounds in middle distillates. This was achieved by investigating the influence of the potential insufficient LC separation of aromatic and aliphatic compound classes. The eluent from the HPLC was fractionized according its elution time and these fractions were subsequently analyzed (offline) by comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS). The methodology was evaluated for common commercial available middle distillates (B0 and B7 Diesel, light heating oil and jet fuel), mixtures of pure diesel fuel with up to 7% hydrogenated vegetable oil (HVO), which serves as an example for a modern advanced premium diesel fuel and different amounts of mono and di-aromatic compounds in HVO as matrix. Compound classes were identified and quantified by applying a data evaluation method which was previously developed in-house [2] for middle distillates based on GC×GC-TOFMS and Visual Basic Scripting (VBS). Our findings show that the deviations between the results obtained by the GCxGC–MS vs. DIN EN 12916 could be attributed to insufficient separation between compound classes when using the DIN EN 12916 method for current middle distillates. The composition of modern fuels furthermore affects the qualitative as well as the quantitative outcome of industrial established standard methods, and that it is pivotal to revise and develop these analytical techniques in a consequential manner as the composition of fuels and petrochemical products will change and be adapted accordingly to legislative, commercial and environmental changes. [ABSTRACT FROM AUTHOR]

Each varietal wine has its own characteristic aroma profile, which can be described by determination of its volatile organic compounds (VOC) profile. The aim of this work was to characterize Gewürztraminer wine using two-dimensional gas chromatography coupled to time-of-flight mass spectrometry, preceded by solid phase microextraction of volatile compounds from headspace, and identify VOC responsible for typical aroma profile of this varietal wine. In 30 wine samples, in total 288 volatiles were identified, while 153 were found in each studied sample. These common attributes creating varietal fingerprint of Gewürztraminer wine were represented by 50 esters, 28 terpenoids and C13-norisoprenoids, 25 higher alcohols, 23 furans, pyrans and lactones, 13 volatile acids, 10 carbonyl compounds, 3 sulphur compounds and 1 volatile phenol. Differentiation among Gewürztraminer wines and wines of other vine varieties was mainly perceived through the following components: cis-rose oxide, sulcatol, (Z)-β-ocimene, 4-vinylguaiacol, furan, 2,5-furandicarboxaldehyde, 2(5H)-furanone, solerone, α-angelica lactone, 2-hydroxy-γ-butyrolactone, β-hydroxybutyrolactone, methyl pyruvate and methyl formate. Regardless of vintage and used technology, in all tested Gewürztraminer samples, VOC previously connected only with oak (maltol), botrytization (p-cymene), non-saccharomyces activity (blackberry thiophenone), insect pheromones or plants other than Vitis vinifera (isogeraniol, β-farnesene, sulcatone, sulcatol, ethyl 3-methylthiopropionate) were identified. [ABSTRACT FROM AUTHOR]

A novel miniaturised single-stage resistively heated thermal modulator was investigated as an alternative to cryogenic modulation for use in comprehensive two-dimensional gas chromatography (GC × GC). The single-stage thermal modulator described herein yielded average retention time relative standard deviations (RSD) of ≤0.2% RSD (first-dimension) and ≤3.4% RSD (second-dimension). The average peak widths generated by the modulator were 72 ± 3 ms, and the peak area precision was better than 5.3% RSD for a range of polar and non-polar test analytes. GC × GC analysis can be performed using this modulator without the requirement for cryogenic cooling or additional pressure control modules for flow modulation. The modulator and associated electronics are compact and amenable towards field analysis. The modulator was used for qualitative and quantitative characterisation of petroleum-contaminated soils derived from a sub-Antarctic research station at Macquarie Island. The limit of detection compared to standard 1D GC analysis was improved from 64 to 11 mg kg −1 . An automated method of analysing and categorising samples using principal component analysis is presented. [ABSTRACT FROM AUTHOR]

Comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC–TOFMS) was used to identify unusual steranes in branched-cyclic hydrocarbon fractions of crude oils from Sergipe-Alagoas Basin, Brazil and infer the geochemical settings of their Cretaceous source rocks. Hopane/sterane and sterane ratios, and the presence of gammacerane and β-carotane in the oil samples indicates a saline source rock depositional environment and predominantly marine organic matter (OM) input. Steroidal hydrocarbons were represented by alkyl steranes and several sterane series, including abundant short-chain steranes (C 21 and C 22 ), regular steranes (C 27 –C 29 ), and diasteranes (C 21 –C 23 , C 27 –C 29 ). The ring-A methyl sterane series contained 3β-methyl steranes (C 22 and C 23 , C 28 –C 30 ), abundant 3β-methyldiginane (C 22 ), and 3β-methyldiacholestanes (C 28 ), including 4-methyl steranes with abundant C 30 4α,23,24-trimethylcholestanes in the branched-cyclic fraction of these crude oils. The C 29 sterane isomers, 23,24-dimethylcholestane and 24-ethylcholestanes, were resolved by GC×GC–TOFMS, and a C 29 dinosterane derivative was identified for the first time in Brazilian crude oils. The 23,24-dimethyl and 4,23,24-trimethyl steroids can be related to dinoflagellate OM and abundant dinosteranes suggests dinoflagellate blooms during source rock deposition in this Brazilian marginal basin. Additionally, the detection of C 28 –C 32 3β-alkyl cholestanes, C 29 –C 33 3β-alkyl 24-methylcholestanes, and C 30 –C 34 3β-alkyl 24-ethylcholestane with ethyl to pentyl groups at C-3 resulted in a complex sterane fingerprint, as expected for petroleum generated from source rocks deposited under predominantly marine saline conditions with high microalgal input. These biomarker results provide additional insight into the character and geologic processes responsible for the source rocks of crude oils in the Brazilian marginal basins. This information will be a valuable exploration tool that can be used to constrain the distribution of different oil types in these basins. [ABSTRACT FROM AUTHOR]

To understand the significance of the trail pheromone used in chemical communication of the leaf-cutting ants Atta opaciceps we investigated, under laboratory conditions, the trail-following behaviour of different castes. We observed a clear behavioural discrimination of conspecific venom gland extract of foraging ants from those of other species. Additionally, we determined the pheromone composition of A. opaciceps venom gland secretion using a two-dimensional gas chromatography coupled with mass spectrometry. Chemical analyses revealed the presence of three nitrogen-containing compounds, identified as 2,5-dimethylpyrazine, 3-ethyl-2,5-dimethylpyrazine and methyl 4-methylpyrrole-2-carboxylate (M4MPC). Four different bioassays performed with workers from different castes of A. opaciceps suggested that the trail pheromone elicits the trail-following behaviour in conspecifics of all castes, but the foragers respond more strongly to their own pheromone than to that of other castes (gardeners, generalists and soldiers). In addition, A. opaciceps foragers follow the trails made with the venom gland extracts of the unrelated Acromyrmex subterraneus subterraneus foragers as well as they follow the trails made with their own venom gland extract. M4MPC was identified to be the most abundant and the most behaviourally active component of the venom gland extract of A. opaciceps foragers. [ABSTRACT FROM AUTHOR]

Abstract Normal and reversed phase column combinations for comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry were evaluated concerning their suitability for the analysis of common commercial available middle distillates. Compound classes were identified and quantified by applying a previously developed data evaluation method (Jennerwein et al., 2014) [1] for middle distillates based on GC × GC-TOFMS using "normal phase" column combination and Visual Basic Scripting (VBS). The GC × GC-TOFMS methodology was transferred to a "reversed phase" column combination and it could be found, that this kind of column combination provides advantages for the quantification of petrochemical samples in terms of precision of the results. Special improvements were observed for the quantification of aromatics and paraffins. [ABSTRACT FROM AUTHOR]

Comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC–TOFMS) was successfully applied to eight real Brazilian Fischer–Tropsch (FT) product samples for the quantitative analysis of O-containing compounds. It not only allowed identifying and quantifying simultaneously a large number of O-containing compounds but also resolved many co-eluting components, such as carboxylic acids, which co-elute in one-dimensional gas chromatography. The homologous series of alcohols and carboxylic acids as trimethylsilyl derivatives were detected and identified at trace levels. The absolute quantification of each compound was accomplished with reliability using analytical curves. Linear alcohols (from C 5 to C 19 ), branched alcohols (C 6 –C 13 ) and carboxylic acids (C 4 to C 12 ) were obtained in the range of 1.58 mg g −1 to 14.75 mg g − 1 , 0.51 mg g − 1 to 1.12 mg g −1 and 0.21 mg g − 1 to 1.63 mg g − 1 of FT product samples, respectively. GC×GC–TOFMS provided a linear range (from 0.3 ng µL −1 to 10 ng µL −1 ), good precision (<8%), and excellent accuracy (recovery range of 77% to 118%) for quantification of individual O-containing compounds in FT product samples. The results can benefit the development of gas-to-liquid technologies from natural gas and guide the choice of an FT conversion process that generates clean products with higher added value. [ABSTRACT FROM AUTHOR]

We review the main analytical methods currently employed for the determination of synthetic musk fragrances in air, aqueous and solid samples, such as sewage sludge or sediments, and biological samples. The review covers instrumental aspects, and procedures for extraction and clean-up. We pay special attention to current trends, such as the replacement of conventional extraction techniques (e.g., liquid-liquid extraction and solid-phase extraction) by microextraction techniques (e.g., solid-phase microextraction and microextraction by packed sorbents) in order to obtain environment-friendly methodologies. We also discuss the applicability of comprehensive two-dimensional gas chromatography and mass spectrometry (MS) or high-resolution MS to enhance the separation of co-eluting compounds and to decrease the matrix effect. Further, we describe a number of degradation assays for the determination of the main transformation products of polycyclic musk fragrances. [ABSTRACT FROM AUTHOR]