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Comprehensive two-dimensional gas chromatography (GC×GC) and high-resolution mass spectrometry (HRMS) offer the best possible separation of their respective techniques. Recent commercialization of combined GC×GC–HRMS systems offers new possibilities for the analysis of complex mixtures. However, such experiments yield enormous data sets that require new informatics tools to facilitate the interpretation of the rich information content. This study reports on the analysis of dust obtained from an electronics recycling facility by using GC×GC in combination with a new high-resolution time-of-flight (TOF) mass spectrometer. New software tools for (non-traditional) Kendrick mass defect analysis were developed in this research and greatly aided in the identification of compounds containing chlorine and bromine, elements that feature in most persistent organic pollutants (POPs). In essence, the mass defect plot serves as a visual aid from which halogenated compounds are recognizable on the basis of their mass defect and isotope patterns. Mass chromatograms were generated based on specific ions identified in the plots as well as region of the plot predominantly occupied by halogenated contaminants. Tentative identification was aided by database searches, complementary electron-capture negative ionization experiments and elemental composition determinations from the exact mass data. These included known and emerging flame retardants, such as polybrominated diphenyl ethers (PBDEs), hexabromobenzene, tetrabromo bisphenol A and tris (1-chloro-2-propyl) phosphate (TCPP), as well as other legacy contaminants such as polychlorinated biphenyls (PCBs) and polychlorinated terphenyls (PCTs). [ABSTRACT FROM AUTHOR]

Sulfur-fumigation could alter the quality of white ginseng by damaging the bioactive compounds and generating sulfur-containing materials. In the present study, coupling needle-trap devices with comprehensive two-dimensional gas chromatography and high-resolution time-of-flight mass spectrometry was applied to rapidly reveal chemical transformation of volatile components from sulfur-fumigated ginseng. Thirty-two volatile compounds were not in white ginseng samples after sulfur-fumigation. Furthermore, 20 sulfur-containing compounds were identified for the first time in volatile oil of sulfur-fumigated white ginseng. The established approach could be applied to discriminate sulfur-fumigated white ginseng among commercial samples and to control the quality of white ginseng. [ABSTRACT FROM AUTHOR]

The volatile fractions of Cape gooseberry and blueberry were determined by headspace solid-phase microextraction coupled with comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (HS-SPME/GC×GC-TOFMS). The highest amount of alcohol (51.8%), ester (32.8%) and carboxylic acid (6.9%) was in blueberry in comparison with gooseberry and oppositely ketones (14.7%), aldehydes (9.9%) and terpenes (8%) were found in gooseberry. The bioactive compounds and antioxidant capacities were higher in blueberries than in gooseberries. Three dimensional fluorescence emission spectrometry (3D-FL) was applied to determine and to compare experimentally found binding parameters of berries extracts with human serum albumin (HSA). The fluorescence quenching of HSA by polyphenols from berries was a result of the formation of a polyphenol–HSA complex. The binding abilities of berries were highly correlated with the bioactivity of polyphenols and volatile substances. The cluster analysis (CA) and linear discriminant analysis (LDA) was applied to differentiate the berries samples according to their type. [ABSTRACT FROM AUTHOR]

Challenges in decomposition odour profiling have led to variation in the documented odour profile by different research groups worldwide. Background subtraction and use of controls are important considerations given the variation introduced by decomposition studies conducted in different geographical environments. The collection of volatile organic compounds (VOCs) from soil beneath decomposing remains is challenging due to the high levels of inherent soil VOCs, further confounded by the use of highly sensitive instrumentation. This study presents a method that provides suitable chromatographic resolution for profiling decomposition odour in soil by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry using appropriate controls and field blanks. Logarithmic transformation and t-testing of compounds permitted the generation of a compound list of decomposition VOCs in soil. Principal component analysis demonstrated the improved discrimination between experimental and control soil, verifying the value of the data handling method. Data handling procedures have not been well documented in this field and standardisation would thereby reduce misidentification of VOCs present in the surrounding environment as decomposition byproducts. Uniformity of data handling and instrumental procedures will reduce analytical variation, increasing confidence in the future when investigating the effect of taphonomic variables on the decomposition VOC profile. [ABSTRACT FROM AUTHOR]

The Slovak-Czech spirit distilled from Sorbus domestica was analyzed by GCxGC with headspace solid phase microextraction and liquid-liquid extraction. Two column combinations, nonpolar × medium-polar and polar × medium-polar were tested. The second column setup provided more exploited 2D separation space with better distribution of peaks in chromatogram. Effects of the first column on the elution order of γ-lactones, benzyl esters, and unsaturated aldehydes in the second separation were observed. More than 500 compounds were detected; nearly 100 were confirmed with standards. [ABSTRACT FROM AUTHOR]

First- and second-dimension retention times for a series of alkyl phosphates were predicted for multiple column combinations in GC×GC. This was accomplished through the use of a three-parameter thermodynamic model where the analytes' interactions with the stationary phases in both dimensions are known. Ionic liquid columns were employed to impart unique selectivity for alkyl phosphates, and it was determined that for alkyl phosphate compounds, ionic liquid columns are best used in the primary dimension. Retention coordinates for unknown phosphates are predicted from the thermodynamic parameters of a set standard alkyl phosphates. Additionally, we present changing retention properties of alkyl phosphates on some ionic liquid columns, due to suspected reaction between the analyte and column. This makes it difficult to accurately predict their retention properties, and in general poses a problem for ionic liquid columns with these types of analytes. [ABSTRACT FROM AUTHOR]

The article presents a study on interactions induced by Salmonella Typhi and Salmonella Paratyphi A during enteric fever among patients participated in a randomized controlled trial at Patan Hospital in Kathmandu, Nepal. Topics discussed include plasma metabolites in enteric fever, results of pattern recognition analysis, and S. Typhi and Paratyphi a specific metabolites.

In the present study, comprehensive 2 D GC- TOF-MS combined with multivariate data analysis was applied to analyze the differences of the volatile components in crude and processed Atractylodis Macrocephalae Rhizoma ( AMR) samples. As a result, 26 compounds that were found in crude AMR samples disappeared in processed AMR samples, and 19 compounds were newly generated and identified in AMR after processing with wheat bran. Meanwhile, principal component analysis demonstrated that there were significant chemical differences between crude and processed AMR samples, and processing procedure caused obvious quantitative and qualitative changes of volatile components in AMR. The established method could be used to explain the chemical differentiation between crude and processed AMR, and to further understand the processing mechanism of herbal medicines. [ABSTRACT FROM AUTHOR]

A comparative analysis of gasoline samples has been performed using several chromatographic methods: one-dimensional detailed hydrocarbon analysis (DHA), which allows for determination of the individual component composition of a liquid petroleum product with identification by retention times; two-dimensional gas chromatography 2D-GC with identification by retention times; two-dimensional gas chromatography 2D-GC-MS with identification by retention times and mass spectra of compounds; and determination of the group composition of gasoline by multidimensional gas chromatography using traps and a reactor with a flame-ionization detector. The advantages and disadvantages of each procedure have been shown and application areas for each method have been specified. [ABSTRACT FROM AUTHOR]

A monolithic column with the optimum structure of its monolithic layer is considered as a second dimension column under the conditions of two-dimensional gas chromatography. It is shown that despite the considerable difference between the working pressures of different columns, sample transfer from a hollow capillary column to a monolithic column is possible when a looped switching valve is used. It is found that the additional broadening of the chromatographic zone observed during sample transfer can be effectively suppressed by using an additional flow splitter. At the same time, reducing the volume of the switching valve loop is inefficient and does not allow effective separation by the monolithic column. [ABSTRACT FROM AUTHOR]

Abstract: Comprehensive two-dimensional gas chromatography (GC×GC) offers advantages over one-dimensional gas chromatography (GC) including, high peak capacity, signal enhancement, and structured chromatograms. These advantages have been exploited to solve several analytical problems that are difficult to achieve in GC. In this review, qualitative and quantitative approaches of GC×GC are explored, including targeted, non-targeted, group, and fingerprinting analysis. [Copyright &y& Elsevier]

Abstract: A new multidimensional chromatographic instrument has been developed to perform both SFC-GC×GC and SFC×GC×GC, in response to the challenge of complex matrices characterization. The design of this online system is fully described and enriched by theoretical and practical discussions. A new interface has been investigated: this interface allows the temporary storage of SFC fractions inside sampling loops before their quantitative transfer toward the GC×GC. This innovative design allows flexible and automatic hyphenated approaches such as single, multiple, total heart-cutting and comprehensive modes. An overview of the interfacing experimental conditions is also presented. Thanks to all the hyphenation possibilities of the three dimensions, this instrument opens up new prospects for the quantitative analysis of very complex matrices. [Copyright &y& Elsevier]

Abstract: The continued development of flow-controlled two-dimensional gas chromatography (2-D GC) is reviewed, with a special emphasis on results published from 2001 through 2011. Heart-cutting 2-D GC continues to be used for isolating selected components in complex mixtures. The programmable and highly precise flows and temperatures produced by modern gas chromatographs have made it easier to selectively transfer analytes to the secondary column and to backflush unwanted components from the primary column. Several new Deans switch interfaces for performing heart-cutting 2-D GC have been introduced, with most attention given to devices that integrate the flow connections into a single unit. Heart-cutting 2-D GC has been used to isolate analytes in a wide variety of complex mixtures including fuels, industrial feedstocks, fragrances, and environmental extracts. Valve-based comprehensive 2-D GC (GC×GC) was also actively developed in the past decade. Valve-based modulation is a simple way to generate GC×GC separations without using cryogenic fluids. More than ten new valve-based modulators were introduced. Diaphragm valves fitted with sample loops are the most common low duty cycle modulators, whereas fluidic modulators that employ differential flow conditions are the most common high duty cycle modulators. Applications of valve-based GC×GC include analysis of hydrocarbon mixtures, essential oils, and environmental samples. [Copyright &y& Elsevier]

Abstract: The intensive development of agriculture means that more and more toxic organic and inorganic compounds are entering the environment. Because of their widespread use, stability, selective toxicity and bioaccumulation, pesticides are among the most toxic substances contaminating the environment. They are particularly dangerous in fruit and vegetables, by which people are exposed to them. It is therefore crucial to monitor pesticide residues in fruit and vegetables using all available analytical methods. We set out the problems in the determination of organonitrogen and organophosphorus pesticides in samples of fruit and vegetables, including the complexity and the diversity of matrices in biological materials, and the very low level of pesticides present, as a result of which target analytes have to be isolated and then enriched prior to final determination. We discuss the various stages in the determination of pesticide residues in fruit and vegetables. We present results from the literature in the context of Maximum Residue Levels (MRLs) of target pesticides in fruit and vegetable samples. We discuss the merits of the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) technique and two-dimensional gas chromatography. [Copyright &y& Elsevier]

Abstract: In gas chromatography (GC) reproducible retention times are in many cases highly favorable or in some cases even required. In one-dimensional GC, retention time shifts can be eliminated or minimized using a procedure called retention time locking (RTL). This procedure is based on adjusting the (constant) column head pressure. Unfortunately, this RTL procedure cannot be used in comprehensive two-dimensional gas chromatography (GC×GC) given the fact that peaks will shift in both dimensions. Adjusting the column head pressure in GC×GC will only minimize or eliminate the primary retention time shifts. In this paper, a fast and easy to perform, two-step retention time locking procedure for two-dimensional gas chromatography (2D-RTL) is proposed and its feasibility is demonstrated. This 2D-RTL procedure involves adjustment of the column head pressure or constant column flow, followed by the adjustment of the so-called effective secondary column length. The secondary column length is increased or decreased, simply by moving it stepwise through the modulator. It is demonstrated that retention time shifts in both the primary- and secondary-dimension, which may occur after e.g. replacing the column set, can be minimized to less than half peak base width. The proposed 2D-RTL procedure is used successfully for approximately 1 year in our laboratory. [Copyright &y& Elsevier]

Abstract: Headspace solid-phase microextraction (HS-SPME) coupled to comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) was applied for equilibrium headspace analysis of Malaysian soursop (Annona muricata) volatile flavor compounds. A two-level fractional factorial design (25-1) was used to determine the effect of SPME variables, namely, SPME fibers, adsorption temperature, extraction time, amount of salt, sample amount and sample concentration on the extraction efficiency of volatile flavor compounds. A total of 37 volatile compounds were identified, comprising 21 esters, 6 alcohols, 3 terpenes, 2 acids, 2 ketones, 2 aldehydes and an aromatic with different hydrophobicities (log P) ranging between −0.14 and 4.83. Extraction using 10g of diluted (5% w/w) blended soursop pulp with CAR/PDMS fiber at 25°C for 30min and 30% (w/w) of NaCl under stirring mode resulted in the highest extraction efficiency of volatile flavor compounds. The principal component analysis score discriminated the influence of SPME variables on the equilibrium headspace concentration of target volatile compounds. [ABSTRACT FROM AUTHOR]

An increase in the production of biodiesel has been accompanied by a rise in the occurrence of biodiesel spills. To determine the source of a spill, fatty acid methyl ester fingerprinting is generally used. However, in the experience of these authors, this approach was of limited use for matching biodiesel residues back to the source material. The present work demonstrates sterol profiling for matching spill samples to a source. Sterol profiling was found to be a better approach for this than fatty acid methyl ester profiling, with the added benefit that sterol analysis could determine the feedstock used in the production of biodiesels. [ABSTRACT FROM AUTHOR]

In this paper, we use a quantitative structure-retention relationship (QSRR) method to predict the retention times of polychlorinated biphenyls (PCBs) in comprehensive two-dimensional gas chromatography (GC×GC). We analyse the GC×GC retention data taken from the literature by comparing predictive capability of different regression methods. The various models are generated using 70 out of 209 PCB congeners in the calibration stage, while their predictive performance is evaluated on the remaining 139 compounds. The two-dimensional chromatogram is initially estimated by separately modelling retention times of PCBs in the first and in the second column ( t and t, respectively). In particular, multilinear regression (MLR) combined with genetic algorithm (GA) variable selection is performed to extract two small subsets of predictors for t and t from a large set of theoretical molecular descriptors provided by the popular software Dragon, which after removal of highly correlated or almost constant variables consists of 237 structure-related quantities. Based on GA-MLR analysis, a four-dimensional and a five-dimensional relationship modelling t and t, respectively, are identified. Single-response partial least square (PLS-1) regression is alternatively applied to independently model t and t without the need for preliminary GA variable selection. Further, we explore the possibility of predicting the two-dimensional chromatogram of PCBs in a single calibration procedure by using a two-response PLS (PLS-2) model or a feed-forward artificial neural network (ANN) with two output neurons. In the first case, regression is carried out on the full set of 237 descriptors, while the variables previously selected by GA-MLR are initially considered as ANN inputs and subjected to a sensitivity analysis to remove the redundant ones. Results show PLS-1 regression exhibits a noticeably better descriptive and predictive performance than the other investigated approaches. The observed values of determination coefficients for t and t in calibration (0.9999 and 0.9993, respectively) and prediction (0.9987 and 0.9793, respectively) provided by PLS-1 demonstrate that GC×GC behaviour of PCBs is properly modelled. In particular, the predicted two-dimensional GC×GC chromatogram of 139 PCBs not involved in the calibration stage closely resembles the experimental one. Based on the above lines of evidence, the proposed approach ensures accurate simulation of the whole GC×GC chromatogram of PCBs using experimental determination of only 1/3 retention data of representative congeners. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The comprehensive two-dimensional gas chromatography (GC×GC) is used as a powerful tool for an improved characterization in sulphur and nitrogen speciation in gasoline. There are shown the results obtained of the connection between GC×GC and a specific detector, sulphur (SCD) and Nitrogen (NCD). This technique is based on the separation of two orthogonal dimensions, achieved by two chromatographic capillary columns with different polarity. The final chromatogram obtained was structured according to the volatility and polarity of hydrocarbons which facilitates its identification. The results are a very promising alternative in the characterization of these types of compounds in middle distillates. This work illustrates the high resolution power of the GC×GC in combination with a selective detection of sulphur or nitrogen compounds in gasoline when a specific detector is used. [ABSTRACT FROM AUTHOR]

Abstract: A study has been conducted to illustrate the benefit of the GC×GC-technique over the classically used 1D-GC technique to analyse the selectivity of iron catalysed low temperature Fischer–Tropsch synthesis. The selectivity of the products obtained from the iron catalysed Fischer–Tropsch synthesis at 225°C; H2/CO feed ratio=1.5 and total pressure=27bars was evaluated. The selectivity results obtained from these methods were compared with special focus on the minor compounds such as oxygenates. The superiority of the GC×GC-technique above the 1D-GC technique were proven when minor product compounds such as the linear acids, secondary alcohols, ketones and aldehydes, and branched paraffins, olefins, alcohols, acids could be quantified using the GC×GC-technique but not using the 1D-GC system. It is further shown that the GC×GC-technique displayed a higher level of accuracy than 1D-GC system when detecting compounds in complex mixtures. [Copyright &y& Elsevier]

Pyrolysis of plastic packaging waste yields a liquid product that can be processed in steam crackers producing light olefins and hence closing the loop towards new virgin plastics. However, there is a lack of knowledge on how the plastic waste composition affects the pyrolysis oil quality regarding hydrocarbon composition and contaminant concentrations. The associated uncertainty is a key reason why thermochemical recycling of contaminated plastic waste is not yet industrially established. In this study, post-consumer plastic packaging waste fractions, namely mixed polyolefins (MPO), polyethylene (PE), and polypropylene (PP) were processed in a continuous pilot-scale pyrolysis unit and the pyrolysis oils subsequently characterized using advanced analytical techniques such as two-dimensional gas chromatography. Substantial amounts of branched olefins (~63 wt%) and diolefins (~20 wt%) were detected in the pyrolysis oil of PP-rich waste, while PE-rich waste produced high amounts of linear paraffins (~34 wt%) and olefins (~26 wt%). Furthermore, significant amounts of nitrogen, oxygen, chlorine, iron, sodium and silicon were detected in the pyrolysis oils exceeding feedstock specifications for industrial steam crackers by orders of magnitude. The results show that next to improved waste sorting and separation processes, pre- and post-treatment techniques are required to produce pyrolysis products suitable for chemical processing. [Display omitted] • Pyrolysis of polyolefinic post-consumer plastic packaging waste. • Comprehensive two-dimensional gas chromatography coupled to various detectors. • PP-pyrolysis yields highly branched olefins, PE-pyrolysis mostly linear compounds. • Nitrogen, oxygen, chlorine, iron, sodium and silicon most important contaminants. • Upgrading or dilution needed when using pyrolysis oils as steam cracker feedstocks. [ABSTRACT FROM AUTHOR]

A simple and effective analytical method for the determination of anabolic steroids and related compounds in nutritional supplements is reported. Target compounds are extracted with ethyl acetate, crude extract is purified using dispersive solid-phase extraction (SPE) with primary secondary amine (PSA) as sorbent, and finally they are identified and quantified as underivatized compounds using two-dimensional gas chromatography with time-of-flight mass spectrometric detection (GCxGC-TOF MS). This method was validated for 25 steroids in two types of commercially available solid nutritional supplements: protein concentrate and creatine monohydrate. Repeatability expressed as the relative standard deviation of analyte concentration ranged from 4.1 to 20.5%. Recoveries between 70.0 and 122.6% were obtained for the target compounds except for oxymetholone in protein concentrate where the recovery was low as a result of strong interactions with PSA. Excellent linearity was obtained for six-point calibration with regression coefficients of 0.997-1.000 for all compounds. The limits of quantification ranged from 0.007 to 0.114 mg kg-1. For a monitoring programme of 48 samples of nutritional supplements, three were positive. Nandrolone, testosterone, dehydroepiandrosterone (DHEA), 5α-androstan-3,17-dione, 19-norandrostendione and progesterone were found in positive samples at concentrations between 0.022 and 0.398 mg kg-1. [ABSTRACT FROM AUTHOR]

Abstract: This article discusses the immunoassay screening of pain management drugs, and the mass spectrometric confirmation of fentanyl in human hair. Hair specimens were screened for fentanyl, opiates (including oxycodone), tramadol, propoxyphene, carisoprodol, methadone, and benzodiazepines and any positive results were confirmed using gas chromatography or liquid chromatography with mass spectral detection. The specific focus of the work was the determination of fentanyl in hair, since autopsy specimens were also available for comparison with hair concentrations. Using two-dimensional gas chromatography with electron impact mass spectrometric detection, fentanyl was confirmed in four of nine hair specimens collected at autopsy. The accuracy of the assay at 10pg/mg was 95.17% and the inter-day and intra-day precision was 5.04 and 13.24%, respectively (n =5). The assay was linear over the range 5–200pg/mg with a correlation of r 2 >0.99. The equation of the calibration curve forced through the origin was y =0.0053x and the limit of quantitation of the assay was 5pg/mg. The fentanyl concentrations detected were 12, 17, 490, and 1930pg/mg and the results were compared with toxicology from routine post-mortem analysis. The screening of pain management drugs in hair is useful in cases where other matrices may not be available, and in routine testing of hair for abused drugs. [Copyright &y& Elsevier]

Crude oils are complex mixtures of many thousands of compounds, both resolved and unresolved by conventional gas chromatography (GC). Recent research using comprehensive two-dimensional gas chromatography-time-of-flight-mass-spectrometry (GC × GC-ToF-MS) identified branched alkylbenzenes (BABs) as a major component of some unresolved complex mixtures of hydrocarbons (UCMs) bioaccumulated in the tissues of North Sea mussels, Mytilus edulis, previously found to have poor health status. Here the effect of long-term exposure to low aqueous concentration of BABs and mussels' ability to recover, was determined. Mussels were exposed to 5 μg/L of a complex mixture of C12-14 BABs for 14 d. Feeding rates and the viability of hemocytes were measured immediately after exposure and again after 5 d depuration. Tissues were extracted, analyzed and alkylbenzenes quantified by both GC-MS and GC × GC-ToF-MS. Mussel extracts from previous acute tests were also reanalyzed and quantified using GC × GC-ToF-MS. Mussels exposed to 5 μg/L BABs for 14 d accumulated 46 to 47 μg/g dry weight alkylbenzenes; this was similar to tissue concentrations of mussels exposed to 41 μg/L for 72 h. Feeding rates were significantly reduced (p ≤ 0.05) and were dependent upon tissue concentration. Cellular viability was not significantly affected. Following 5 d in clean seawater, the BABs were only partially depurated and feeding rates failed to fully recover. The use of GC × GC-ToF-MS in the present study has shown that mussel tissue concentrations of complex mixtures of alkylbenzenes, and their corresponding effects, are consistent with reported concentrations within UCM-contaminated wild mussel populations with poor health status. [ABSTRACT FROM AUTHOR]

Abstract: First, standard mixtures of trimethylsilyl (TMS) derivatives of amino acid and organic acid are analyzed by comprehensive two-dimensional (2D) gas chromatography (GC) coupled to time-of-flight mass spectrometry (GC × GC/TOFMS) in order to illustrate important issues regarding application of the technique. Specifically of interest is the extent to which the peak capacity of the 2D separation space has been utilized and the procedure by which the derivative standards are identified in the 2D separations using the mass spectral information. The resulting 2D separation is found to make extensive use of the GC × GC separation space provided by the complementary stationary phases employed. Second, in order to demonstrate GC × GC/TOFMS on two real sample types, trimethylsilyl metabolite derivatives were analyzed from extracts of common lawn grass samples (i.e., perennial rye grass), as a means to provide insight into both the pre and post harvest physiology. Various chemical components in the two rye grass extract samples were found to either emerge or disappear in relation to the trauma response. For example, a significant difference in the peak for the TMS derivative of malic acid was found. The successful analysis of various components was readily facilitated by the 2D separation, while a 1D separation would have produced too much peak overlap, thus impeding the analysis. The importance of using a GC × GC separation approach for the analysis of complex samples, such as metabolite extracts, is therefore demonstrated. The real-time analysis capability of GC × GC/TOFMS for multidimensional metabolite analysis makes this technique well suited to the high-throughput analysis of metabolomic samples, especially compared to slower, stopped-flow type separation approaches. [Copyright &y& Elsevier]

Cotton seed was submitted to fast pyrolysis in a fixed bed reactor and the liquid and solid products were characterized applying several techniques. The detailed chemical composition of the bio-oil was investigated using GC × GC/TOFMS combined with software tools and retention index. A total of 257 compounds were tentatively identified with 168 were confirmed by LTPRI. The most abundant compounds identified in the cotton seed bio-oil were nitrogenous (56 compounds) and phenolic (42 compounds) what distinguishes this bio oil from others, produced from various sources of biomass. The higher heating values of cotton seed and bio-oil were 19.34 MJ kg −1 and 34.25 MJ kg −1 respectively and demonstrating the feasibility of the use of cotton seed in its natural form for energy generation or as a secondary source once a bio-oil with these characteristics would be a suitable candidate for use in boilers for heating purposes or chemical extraction. The biochar had a significant carbon content and a high heating value (22.12 MJ kg −1), making it attractive for fuel applications. The activation methods used were able to improve the physical and chemical characteristics of the biochar, as demonstrated by methylene blue adsorption tests. The maximum adsorption capacity of NaOH-activated biochar was 23.82 mg g −1 while that of K 2 CO 3 -activated biochar was 332.40 mg g −1. [Display omitted] • First report of effective application of biochar from cotton seed as adsorbent. • Biochar with high surface area (1221 m2 g−1) and adsorption capacity (332 mg g−1). • High performance chromatography identified more than 200 compounds in the bio-oil. • Differentiated bio-oil produced with nitrogenous and phenolic compounds as major. [ABSTRACT FROM AUTHOR]

Frontal gland secretions of termite soldiers of the species Nasutitermes costalis, N. ephratae, N. nigriceps, N. rippertii, and N. hubbardii were analyzed. The chiral compositions of the monoterpene hydrocarbons were investigated by means of two-dimensional gas chromatography. Two of them, 3-carene and β-pinene were present in the form of (−)-enantiomers of high purity in the majority of the samples. The other monoterpenes, α-pinene, camphene, sabinene, limonene, and β-phellandrene, exhibited a great variation in the enantiopurity between different species. α-Pinene and limonene varied significantly even between different colonies within the species. N. costalis was the only species with an invariable composition of the secretion, independent of the locality or origin. [ABSTRACT FROM AUTHOR]

Abstract Background The mechanism behind the lowered postprandial insulin demand observed after rye bread intake compared to wheat bread is unknown. The aim of this study was to use the metabolomics approach to identify potential metabolites related to amino acid metabolism involved in this mechanism. Methods A sourdough fermented endosperm rye bread (RB) and a standard white wheat bread (WB) as a reference were served in random order to 16 healthy subjects. Test bread portions contained 50 g available carbohydrate. In vitro hydrolysis of starch and protein were performed for both test breads. Blood samples for measuring glucose and insulin concentrations were drawn over 4 h and gastric emptying rate (GER) was measured. Changes in the plasma metabolome were investigated by applying a comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry metabolomics platform (GC×GC-TOF-MS). Results Plasma insulin response to RB was lower than to WB at 30 min (P = 0.004), 45 min (P = 0.002) and 60 min (P < 0.001) after bread intake, and plasma glucose response was significantly higher at time point 90 min after RB than WB intake (P = 0.045). The starch hydrolysis rate was higher for RB than WB, contrary to the in vitro protein digestibility. There were no differences in GER between breads. From 255 metabolites identified by the metabolomics platform, 26 showed significant postprandial relative changes after 30 minutes of bread intake (p and q values < 0.05). Among them, there were changes in essential amino acids (phenylalanine, methionine, tyrosine and glutamic acid), metabolites involved in the tricarboxylic acid cycle (alpha-ketoglutaric, pyruvic acid and citric acid) and several organic acids. Interestingly, the levels of two compounds involved in the tryptophan metabolism (picolinic acid, ribitol) significantly changed depending on the different bread intake. Conclusions A single meal of a low fibre sourdough rye bread producing low postprandial insulin response brings in several changes in plasma amino acids and their metabolites and some of these might have properties beneficial for health.

Seventy-six organic acids in urine specimens are determined with quantitative two-dimensional gas chromatography-time-of-flight mass spectrometry (GCxGC-TOFMS). The specimen is treated with urease to remove urea and then derivatized to form pentafluorobenzyl oximes (PFBO) of oxo-acids. The sample is then treated with ethyl alcohol to precipitate proteins and centrifuged. After drying the supernatant, the organic acids are derivatized to form volatile trimethylsilyl (TMS) derivatives for separation by capillary two-dimensional gas chromatography (GCxGC) with temperature programming and modulation. Detection is by time-of-flight mass spectrometry (TOFMS) with identification of the organic acids by their mass spectra. Organic acids are quantitated by peak areas of reconstructed ion chromatograms with internal standards and calibration curves. Organic acids are quantified to determine abnormal patterns for the diagnosis of more than 100 inherited disorders of organic acid metabolism. Characteristic abnormal metabolites are quantified to monitor dietary and other modes of treatment for patients who are diagnosed with specific organic acid disorders., (© 2022. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

• Metabolomic differences between farmed and pacu fish were analyzed. • Principal component analysis discovered class-distinguishing features between samples. • PC loadings were examined to find the 50 most highly loaded analytes. • Concentration ratios and p-values were calculated for all 50 metabolites. • 34/50 metabolites were significantly different between farmed and control fish. Pacu fish are an important source of revenue and food supply in Argentina, however the nutritional effects of raising these fish in an integrated rice-fish farming environment on the fish metabolome are still unclear. To investigate this issue, the discovery of class-distinguishing compounds between farmed and control pacu fish samples was performed by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC-TOFMS) followed by principal component analysis (PCA). Pacu fish muscle tissue samples were extracted and derivatized for a total of 10 farmed and 10 control fish prior to GC × GC-TOFMS analysis. The total ion current (TIC) and a diagnostic ion for sugars, mass channel (m / z) 217, data for each fish were input to PCA for the non-targeted discovery of metabolites that differentiated between the control and farmed samples. The scores revealed that the classes (farmed and control fish) separated best on PC2, with most of the variance captured on PC1 accounting for the within class variance when both the TIC and m / z 217 were used. The loadings were examined to retrieve the 50 most highly loaded analytes on PC1 and PC2 using the TIC and m / z 217 (a compiled list of the 20 most highly loaded variables on each PC for the TIC and m / z 217), which were subsequently identified and concentration ratios, [Farmed]/[Control], were calculated to determine how farming fish with rice affects metabolite concentrations in pacu fish muscle tissue. A majority of analytes are downregulated in the farmed pacu fish (39/50) with 30 of these passing a p-value threshold at the 95% confidence level while of the remaining 11 analytes that were upregulated, 4 analytes passed a p-value threshold (34 analytes total passing the p-value threshold). Many of these significant analytes were highly loaded on PC2 and are involved in important metabolic processes including protein catabolism or nucleotide metabolism and tissue repair. These PCA results provide meaningful insight into the effects of farming Argentinian pacu fish with rice fields on the fish metabolome. [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. [ABSTRACT FROM AUTHOR]

• Chemical compositional analysis of cicada wing nanosurfaces for species comparison. • GC × GC provides resolving power essential for trace analysis in biological samples. • Species-specific molecules were observed and linked to wing functionality. • Trace analysis by GC × GC-MS has the potential to determine insect location history. Cicada wings exhibit several intriguing properties that arise from a combination of nanopillar structures and chemical constituents, including superhydrophobicity, as well as antimicrobial, antireflective, and self-cleaning functions. While the physical dimensions of the nanofeatures are relatively simple to characterize through microscopy, the chemicals that cover these pillars are more difficult to characterize due to the variety and complexity of the mixture. Here, we compared the extractable chemicals from the wing surfaces of two different cicada species using both gas chromatography time-of-flight mass spectrometry (GC-TOFMS) and two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC-TOFMS) platforms. Chemical extracts from Neotibicen pruinosus and Magicicada septendecim cicada wings were separated and analyzed. The GC × GC-TOFMS platform was able to isolate and identified roughly three times the number of constituents as the GC-TOFMS platform at a signal-to-noise ratio (SNR) ≥10.0 and spectral similarity ≥800. When comparing the two cicada species wing extracts, the two-dimensional platform was able to expose differences in the chemical composition that were undetectable by the one-dimensional technique. GC × GC-TOFMS revealed nearly four times the number of unique species-specific compounds as compared to the number identified by GC-TOFMS. Further, surface chemicals were identified that are likely xenobiotics and can pinpoint location and contamination from where the cicada was collected. While the advantages of GC × GC-TOFMS over GC-TOFMS have been documented in the past, our work presents a powerful biological application of GC × GC-TOFMS with promise to reveal both organism species-specific biomarkers while providing insight into the environmental conditions of individual organisms. [ABSTRACT FROM AUTHOR]

Arsonous wildfires are complex investigations due to the high abundance of natural background compounds and subsequent pyrolysis by-products formed during combustion. These interfering compounds can be present in large concentrations and overwhelm the marker compounds used to identify ignitable liquid residue (ILR). Complex matrix effects often interfere with the identification of ILR, providing ambiguous results. The use of comprehensive two-dimensional gas chromatography with time of flight mass spectrometry (GC×GC-TOFMS) separates natural compounds from interfering with ILR compounds of interest. When compared to standard gas chromatography-mass spectrometry (GC-MS) analysis, GC×GC was able to reduce the number of tentative results by 20%. Certain compounds were determined to be unusable for the identification of ILR in wildfire debris samples, in particular the Three Musketeer Group (ethylbenzene, m,p-xylene, and o-xylene), which are ubiquitous in all samples, as well as long chain n-alkylbenzenes, which are formed in the pyrolysis of organic matter. Conversely, the presence of C1- and C2-alkylnaphthalenes were excellent indicators of the presence of gasoline-type ILR. A sizeable number of background samples were collected that helped to provide additional lines of evidence when classifying samples for ILR. Given the complicated matrices encountered in arsonous wildfires, it is evident that GC×GC provides better capabilities at identifying ILR than the standard GC-MS analytical technique. [ABSTRACT FROM AUTHOR]

Indigenous Salvia species from southern Africa are popular traditional medicines for the treatment of a variety of conditions. They produce fragrant volatiles that can be isolated as essential oils. Some of these volatile organic compounds may play a role in the biological activities of the extracts. Three indigenous Salvia species, Salvia africana-lutea , S. lanceolata and S. chamelaeagnea , were selected for this study as they are commonly used in traditional medicine in South Africa, and the essential oils from these species have potential for commercialisation. Although some studies have described the essential oil compositions and some biological activities, only single composite samples were used. The aim of this study was to investigate the intra- and interspecies variation of the essential oils, sampled over a wide geographical area and using a representative sample size, to encourage commercialisation of the essential oil. Essential oils were isolated from individual plants using conventional hydrodistillation of the aerial parts, harvested from several localities. Gas chromatography coupled simultaneously to mass spectrometry/flame ionisation detection (GC-MS/FID) was used to identify and quantify the volatile constituents. The essential oils of S. africana-lutea consisted mainly of terpinene-4-ol + β-caryophyllene (1.4 – 29.0%), T-cadinol (1.2 – 20.0%), α-eudesmol (trace – 23.0%) and β-eudesmol (trace – 26.0%), those of S. lanceolata comprised mainly terpinene-4-ol + β-caryophyllene (4.3 – 31.0%), α-humulene (2.3 – 15.0%), bicyclogermacrene (trace – 37.0%) and spathulenol (trace – 25.0%), while the essential oils of S. chamelaeagnea were characterised by δ-3-carene (trace – 18.0%), limonene (1.6 – 36.0%), viridiflorol (9.8 – 61.0%) and 1,8-cineole (not detected – 11.0%). The compounds identified in the essential oils of the three selected Salvia species have been identified in other Salvia essential oils. To add to the novelty of this study, the superior resolving power of two-dimensional gas chromatography was demonstrated through analysis of selected essential oils. Many additional compounds were identified, and previously co-eluting compounds were clearly separated. Chemometric modelling of the GC-MS data using SIMCA P+ 14 software allowed distinct clustering patterns to be discerned. The unsupervised principal component analysis model revealed separate clusters for the three species, confirming substantial chemical differences between their essential oils. Quantitative, rather than qualitative differences were evident when individual essential oil samples representing the same species, were compared. For each species, two chemically distinct groups were observed and unique marker compounds could be identified. This study has contributed detailed information on the major and minor volatile compounds present in the essential oils of the three Salvia species investigated. Image 1 • Inter and intraspecies variation revealed for essential oils of three Salvia species. • Major compounds identified for each species by GC-MS. • Two-dimensional gas chromatography reveals more and separates overlaps. • Chemical markers and chemotypes identified by use of chemometrics. [ABSTRACT FROM AUTHOR]

• Data-driven approaches for GCxGC retention time predictions. • 3D electrostatic potential and CNN were utilized to develop 3D-QSRR models. • CNN are able to learn geometric information which improves model prediction. • Retention time prediction and HRMS information enable untargeted steroid annotation. Untargeted steroid identification represents a great analytical challenge even when using sophisticated technology such as two-dimensional gas chromatography coupled to high resolution mass spectrometry (GC × GC HRMS) due to the chemical similarity of the analytes. Moreover, when analytical standards, mass spectral and retention index databases are not available, compound annotation is cumbersome. Hence, there is a need for the development of retention time prediction models in order to explore new annotation approaches. In this work, we evaluated the use of several in silico methods for retention time prediction in multidimensional gas chromatography. We use three classical machine learning (CML) algorithms (Partial Least Squares (PLS), Support Vector Regression (SVR) and Random Forest Regression (RFR)) and two deep learning approaches (dense neural network (DNN) and three-dimensional convolutional neural network (CNN)). Whereas molecular descriptors were utilized for the CLM and DNN algorithms, three-dimensional molecular representation based on the electrostatic potential (ESP) was studied as input data as is for the CNN. All the developed models showed similar performances with Q2 values over 0.9. However, among all CNN showed the best performance, resulting in average retention time prediction errors of 2% and 6% for the first and second separation dimension, respectively. Additionally, only the three-dimensional ESP representation coupled with CNN was able to extract the stereochemical information crucial for the separation of diastereomers. The combination of retention time prediction and high-resolution mass spectral data applied to clinical samples enabled the untargeted annotation of 12 steroid metabolites in the urine of new-borns. [ABSTRACT FROM AUTHOR]

• GC × GC-HRTOFMS analysis of Tokaj varietal wines produced from three grape cultivars. • Detection of compounds (1(3H)-isobenzofuranone, ethyl 1H-indole-3-acetate and 2-(methylmercapto)benzothiazole) which were not previously found in wine. • Reliable identification and separation of acetamides, heterocyclic and sulphur containing compounds. • Quantification of trace compounds like lactones and terpenes in Tokaj varietal wines. Botrytised wines produced in Tokaj region belong to a special category of sweet wines described with a pleasant honey-like taste and a distinctive fruit flavour. Specific technological process of wine-making developed on macerating of noble-rotten berries in fermented juice or wine, results in alcoholic beverage indicated with the 'Protected Designation of Origin' label. A limited number of publications is devoted to analysis of Tokaj wines or by-products (e.g. individual varietal wines, essencia and must) which directly related to final characteristics of botrytized wine. A combination of two-dimensional gas chromatography connected to high-resolution mass spectrometry (GC × GC-HRTOFMS) offers enhanced separation and reliable identification of organic compounds presented in complex samples. In our study, this technique was applied to analyse varietal wines of the Tokaj wine region produced from three main grape cultivars (Furmint, Lipovina and Muscat Blanc à Petits Grains). The primary task was reliable separation and identification of low volatility compounds (acetamides, 2H-pyrrole- and 2H-pyran-based heterocyclic compounds and sulphur containing compounds) because of the lack of available information in this area. Thus, it revealed the presence of 1(3H)-isobenzofuranone, ethyl 1H-indole-3-acetate and 2-(methylmercapto)benzothiazole which were not previously detected in wine. Furthermore, trace aroma compounds (terpenoids and lactones) was quantified with modified stir bar sorptive extraction method which provided LOD and LOQ values of 2.3–4.7 ng/L and 7.7–15.8 ng/L, respectively. Linear calibration dependencies with correlation coefficients varying between 0.960 – 0.996 were obtained. Image, graphical abstract [ABSTRACT FROM AUTHOR]