Gas Chromatography Coupled To Time-of-flight Mass Spectrometry Research Articles

A Systematic Review of Polycyclic Aromatic Hydrocarbon Derivatives: Occurrences, Levels, Biotransformation, Exposure Biomarkers, and Toxicity.

Polycyclic aromatic hydrocarbon (PAH) derivatives constitute a significant class of emerging contaminants that have been ubiquitously detected in diverse environmental matrixes, with some even exhibiting higher toxicities than their corresponding parent PAHs. To date, compared with parent PAHs, fewer systematic summaries and reanalyses are available for PAH derivatives with great environmental concerns. This review summarizes the current knowledge on the chemical species, levels, biotransformation patterns, chemical analytical methods, internal exposure routes with representative biomarkers, and toxicity of PAH derivatives, primarily focusing on nitrated PAHs (NPAHs), oxygenated PAHs (OPAHs), halogenated PAHs (XPAHs), and alkylated PAHs (APAHs). A collection of 188 compounds from four categories, 44 NPAHs, 36 OPAHs, 56 APAHs, and 52 XPAHs, has been compiled from 114 studies that documented the environmental presence of PAH derivatives. These compounds exhibited weighted average air concentrations that varied from a lower limit of 0.019 pg/m3 to a higher threshold of 4060 pg/m3. Different analytical methods utilizing comprehensive two-dimensional gas chromatography coupled with high-resolution time-of-flight mass spectrometry (GC × GC-TOF-MS), gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS), comprehensive two-dimensional gas chromatography coupled to quadrupole mass spectrometry (GC × GC-QQQ-MS), and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), that adopted untargeted strategies for the identification of PAH derivatives are also reviewed here. Additionally, an in-depth analysis of biotransformation patterns for each category is provided, including the likelihood of specific biotransformation reaction types. For the toxicity, we primarily summarized key metabolic activation pathways, which could result in the formation of reactive metabolites capable of covalently bonding with DNA and tissue proteins, and potential health outcomes such as carcinogenicity and genotoxicity, oxidative stress, inflammation and immunotoxicity, and developmental toxicity that might be mediated by the aryl hydrocarbon receptor (AhR). Finally, we pinpoint research challenges and emphasize the need for further studies on identifying PAH derivatives, tracking external exposure levels, evaluating internal exposure levels and associated toxicity, clarifying exposure routes, and considering mixture exposure effects. This review aims to provide a broad understanding of PAH derivatives' identification, environmental occurrence, human exposure, biotransformation, and toxicity, offering a valuable reference for guiding future research in this underexplored area.

Effect of Interactions between Phosphorus and Light Intensity on Metabolite Compositions in Tea Cultivar Longjing43

Light intensity influences energy production by increasing photosynthetic carbon, while phosphorus plays an important role in forming the complex nucleic acid structure for the regulation of protein synthesis. These two factors contribute to gene expression, metabolism, and plant growth regulation. In particular, shading is an effective agronomic practice and is widely used to improve the quality of green tea. Genotypic differences between tea cultivars have been observed as a metabolic response to phosphorus deficiency. However, little is known about how the phosphorus supply mediates the effect of shading on metabolites and how plant cultivar gene expression affects green tea quality. We elucidated the responses of the green tea cultivar Longjing43 under three light intensity levels and two levels of phosphorus supply based on a metabolomic analysis by GC×GC-TOF/MS (Two-dimensional Gas Chromatography coupled to Time-of-Flight Mass Spectrometry) and UPLC-Q-TOF/MS (Ultra-Performance Liquid Chromatography-Quadrupole-Time of Flight Mass Spectrometry), a targeted analysis by HPLC (High Performance Liquid Chromatography), and a gene expression analysis by qRT-PCR. In young shoots, the phosphorus concentration increased in line with the phosphate supply, and elevated light intensities were positively correlated with catechins, especially with epigallocatechin of Longjing43. Moreover, when the phosphorus concentration was sufficient, total amino acids in young shoots were enhanced by moderate shading which did not occur under phosphorus deprivation. By metabolomic analysis, phenylalanine, tyrosine, and tryptophan biosynthesis (PTT) were enriched due to light and phosphorus effects. Under shaded conditions, SPX2 (Pi transport, stress, sensing, and signaling), SWEET3 (bidirectional sugar transporter), AAP (amino acid permeases), and GSTb (glutathione S-transferase b) shared the same analogous correlations with primary and secondary metabolite pathways. Taken together, phosphorus status is a crucial factor when shading is applied to increase green tea quality.

P003 Metabolomics for improved patient stratification in inflammatory bowel disease: Characterisation of the ulcerative colitis metabolome

Abstract Background The onset of ulcerative colitis (UC) is characterised by a dysregulated mucosal immune response triggered by several genetic and environmental factors in the context of host-microbe interaction. This complexity makes UC ideal for metabolomic studies to unravel the disease pathobiology and to improve the patient stratification strategies toward personalised medicine. This study aims to explore the mucosal metabolomic profile in treatment-naïve and deep remission UC patients, and to define the metabolic signature of UC. Methods Treatment-naive UC patients (n = 18), UC patients in deep remission (n = 10), and healthy volunteers (n = 14) were recruited. Mucosa biopsies were collected during colonoscopy. The UC activity and the state of deep remission were assessed by endoscopy, histology, and by measuring TNF gene expression. Metabolomic analysis was performed by combined gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) and ultra-high performance liquid chromatography coupled with mass spectrometry (UHPLC-MS). In total, 177 metabolites from 50 metabolic pathways were identified. Results Multivariate data analysis revealed a distinct metabolomic profile in inflamed mucosa taken from treatment- naïve UC patients compared with non-inflamed mucosa taken from UC remission patients and healthy controls. The mucosal metabolome in UC remission patients differed to a lesser extent from the healthy controls. The most prominent metabolome changes among the study groups were in lysophosphatidylcholine, acylcarnitine, and amino acid profiles. Several metabolic pathways were perturbed, ranging from amino acid metabolism (such as tryptophan metabolism, and alanine, aspartate and glutamate metabolism) to antioxidant defence pathway (glutathione pathway). Furthermore, the pathway analysis revealed a disruption in the long-and short-chain fatty acid (LCFA and SCFA) metabolism, namely linoleic metabolism and butyrate metabolism. Conclusion The mucosal metabolomic profiling revealed a metabolic signature during the onset of UC, and reflected the homeostatic disturbance in the gut. The altered metabolic pathways highlight the importance of system biology approaches to identify key drivers of IBD pathogenesis which prerequisite personalised treatment.

Overexpression of Ricinus communis L. malate synthase enhances seed tolerance to abiotic stress during germination

Ricinus communis L. seeds can germinate at high temperatures, but further development of the seedlings is negatively affected. This mainly caused by impairment of energy-generating pathways when seeds are germinated at 35 °C. Ricinus communis malate synthase (RcMLS) is a key responsive gene in lipid mobilization and gluconeogenesis and as such might have a role in sustaining successful seed germination and seedling growth. Herein, we raised the question whether RcMLS might be involved in the biochemical and molecular mechanisms required for R. communis seed germination under unfavourable environmental conditions. For that, we used a robust approach that encompassed bioinformatics analysis, transgenic Arabidopsis thaliana (L.) Heynh seeds overexpressing RcMLS, along with phenotypical characterization of seed germination under abiotic stress. The phylogenetic tree revealed important evolutionary relationship amongst MLS sequences from R. communis and from other crop species/model plants. Overexpression of RcMLS enhanced A. thaliana seed germination under high temperature and salt stress. For example, wild-type A. thaliana Columbia seeds (Col-0) showed 37 % of maximum germination at 35 °C, whereas A. thaliana seeds overexpressing RcMLS showed up to 71%. When salt stress was applied (75 mM NaCl), maximum germination of Col-0 seeds reached 37%, whereas for A. thaliana seeds overexpressing RcMLS it reached up to 93%. Nuclear Magnetic Resonance (NMR) and Gas Chromatography coupled to Time-Of-Flight Mass Spectrometry (GC-TOF-MS) metabolomics analysis showed a robust metabolic signature of A. thaliana seeds overexpressing RcMLS in response to abiotic stress. They accumulated high levels of Met, Ile, fructose, glucose, and sucrose. Therefore, we suggested that overexpression of RcMLS has modulated the glyoxylate cycle and gluconeogenesis pathway in order to maintain cellular homeostasis under unfavorable environmental conditions. Our results provide important leads into the contribution of RcMLS to the underlying mechanism of R. communis seed germination under adverse environmental conditions. This might be helpful for breeding programs to develop more resistant R. communis cultivars which are more likely to sustain growth and high yield under the severe conditions found in arid and semi-arid areas worldwide.

Mucosal Metabolomic Profiling and Pathway Analysis Reveal the Metabolic Signature of Ulcerative Colitis

The onset of ulcerative colitis (UC) is characterized by a dysregulated mucosal immune response triggered by several genetic and environmental factors in the context of host–microbe interaction. This complexity makes UC ideal for metabolomic studies to unravel the disease pathobiology and to improve the patient stratification strategies. This study aims to explore the mucosal metabolomic profile in UC patients, and to define the UC metabolic signature. Treatment- naïve UC patients (n = 18), UC patients in deep remission (n = 10), and healthy volunteers (n = 14) were recruited. Mucosa biopsies were collected during colonoscopies. Metabolomic analysis was performed by combined gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) and ultra-high performance liquid chromatography coupled with mass spectrometry (UHPLC-MS). In total, 177 metabolites from 50 metabolic pathways were identified. The most prominent metabolome changes among the study groups were in lysophosphatidylcholine, acyl carnitine, and amino acid profiles. Several pathways were found perturbed according to the integrated pathway analysis. These pathways ranged from amino acid metabolism (such as tryptophan metabolism) to fatty acid metabolism, namely linoleic and butyrate. These metabolic changes during UC reflect the homeostatic disturbance in the gut, and highlight the importance of system biology approaches to identify key drivers of pathogenesis which prerequisite personalized medicine.

Identification of Gut Microbiota and Metabolites Signature in Patients With Irritable Bowel Syndrome

Background and Aims: Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder. However, the underlying mechanism of IBS is not fully understood. The aim of this study was to investigate potential mechanism and novel biomarkers of IBS through evaluation of the metabolomic and microbiologic profile.Methods: Fecal samples were collected from 15 irritable bowel syndrome patients and 15 healthy controls. By using gas chromatography coupled to time-of-flight mass spectrometry (GC-TOFMS) and 16S rDNA amplicon sequencing, fecal metabolites and microbiota of healthy controls and the IBS patients were measured.Results: IBS patients had a significantly differential metabolite profile as compared to healthy controls, and 4 clusters with 31 metabolites, including a group of amino acids and fatty acids, were significantly up-regulated as compared to the healthy controls. In addition, 19 microbes were significantly up-regulated, and 12 microbes were down-regulated in the IBS group, when compared with the healthy controls. Some clusters of fecal metabolites or microorganisms were significantly correlated with the severity of IBS symptoms, such as the frequency of abdominal pain/discomfort and the number of bowel movements. Correlation of the metabolite levels with abundances of microbial genera showed some statistically significant metabolite-microbe associations. Four differentially abundant amino acids clustered together were positively correlated with some microbes, including Lachnospira, Clostridium, and so on.Conclusion: The finding of this study puts a global perspective on metabolomics and microbiota profiling in IBS patients and provides a theoretical basis for future research on pathophysiology of IBS.

Multi-omics Analysis of Gut Microbiota and Metabolites in Rats With Irritable Bowel Syndrome.

Irritable bowel syndrome (IBS) is a common gastrointestinal dysfunctional disease. The pathophysiology of IBS is, however, largely unknown. This study aimed to determine whether evaluation of fecal metabolite and microbiota profiles may offer an opportunity to identify a novel pathophysiological target for IBS, and to reveal possible gut microbe–metabolite associations. By using gas chromatography coupled to time-of-flight mass spectrometry (GC-TOFMS) and 16S rRNA gene sequencing, we measured fecal metabolites and microbiota of the control and water avoidance stress (WAS)-induced IBS rats. We found a significantly differential metabolite profile between the IBS and control groups; a cluster of metabolites was also found to be significantly associated with the amount of defecations. Moreover, the WAS group exhibited a decreased alpha diversity of the microbial population as compared to the control group. However, the characteristics of gut microbiota could not differentiate the IBS group from the control group. Correlation of the metabolite level with the number of microbial genera showed no significant association between the control and IBS groups. This study provides a global perspective on metabolomics and microbiota profiling in WAS-induced IBS model and a theoretical basis for research on the pathophysiology of IBS.

Jejunal Metabolic Responses to Escherichia coli Infection in Piglets.

This study aimed to investigate the jejunal metabolic variations in enterotoxigenic Escherichia coli (ETEC)-infected piglets. Piglets were infected with 1 × 1010 CFUs (colony-forming units) of ETEC W25K and assigned into diarrheal, recovered, control, and resistant groups. Jejunal samples were harvested at day 6 and metabolic profiles were analyzed via gas chromatography coupled to time-of-flight mass spectrometry (GC/TOFMS). The results showed that 33 metabolites in the jejunum were identified in ETEC-induced diarrhea, including amino acids, fatty acids, sugars, and organic acids. Compared with the control, resistant, and recovered piglets, diarrheal piglets showed higher concentrations of 4-aminobutyric acid (GABA) and glycine in the jejunum. Compared with the control and resistant piglets, six metabolites were markedly decreased in diarrheal piglets, including ornithine, asparagine, glutamine, citric acid, citrulline, and lysine. Collectively, this study provides insights into jejunal metabolic response to ETEC infection and ETEC induced diarrhea in piglets.

Effects of brown rice on cellular growth and metabolic changes in mice

The consumption of rice, especially brown rice, is known to promote cellular growth but the underlying mechanisms and key metabolites of this process are unclear. This study investigated the effects of brown rice on cellular growth and the underlying mechanisms using a metabolomics approach in vivo. C57BL/6J male mice were fed an isocaloric diet composed of control chow, Ilpum rice (IP; Oryza sativa L. cv. Ilpum), or Ilpum brown rice (IB) for 4weeks, and then the metabolites of the liver were analyzed. The rice consumption reduced the liver enzyme levels in plasma and did not result in obesity. The plasma total-cholesterol levels were significantly reduced in the IB group compared with the IP group. The plasma concentrations of growth hormone and insulin growth factor-1 were significantly increased, along with increased thigh bone width in the IB group compared with the IP group, suggesting that the intake of brown rice promoted animal growth. Gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) was used for the metabolic profiling of liver samples obtained from IP- and IB-fed mice. The obtained data sets were subjected to multivariate statistical analysis to investigate which metabolites contributed to the differences between the IP and IB groups. GC-TOF-MS analysis revealed the presence of 31 metabolites consisting of 8 lipids, 4 sugars and sugar alcohols, 15 amino acids, and 4 organic acids. Partial least-squares regression analysis demonstrated significant correlations between the data collected from GC-TOF-MS and the levels of growth hormone. The levels of l-valine, l-glutamine, and d-mannose were significantly higher in the IB group than the control and IP groups.

Effect of Environment and Genotype on Commercial Maize Hybrids Using LC/MS-Based Metabolomics

We recently applied gas chromatography coupled to time-of-flight mass spectrometry (GC/TOF-MS) and multivariate statistical analysis to measure biological variation of many metabolites due to environment and genotype in forage and grain samples collected from 50 genetically diverse nongenetically modified (non-GM) DuPont Pioneer commercial maize hybrids grown at six North American locations. In the present study, the metabolome coverage was extended using a core subset of these grain and forage samples employing ultra high pressure liquid chromatography (uHPLC) mass spectrometry (LC/MS). A total of 286 and 857 metabolites were detected in grain and forage samples, respectively, using LC/MS. Multivariate statistical analysis was utilized to compare and correlate the metabolite profiles. Environment had a greater effect on the metabolome than genetic background. The results of this study support and extend previously published insights into the environmental and genetic associated perturbations to the metabolome that are not associated with transgenic modification.

Metabonomic analysis of liver tissue from BALB/c mice with d-galactosamine/lipopolysaccharide-induced acute hepatic failure

BackgroundCompared with biofluids, target tissues and organs more directly reflect the pathophysiological state of a disease process. In this study, a D-galactosamine (GalN) / lipopolysaccharide (LPS)-induced mouse model was constructed to investigate metabonomics of liver tissue and directly characterize metabolic changes in acute liver failure (ALF).MethodsAfter pretreatment of liver tissue, gas chromatography coupled to time-of-flight mass spectrometry (GC/TOFMS) was used to separate and identify the liver metabolites. Partial least squares – discriminant analysis models were constructed to separate the ALF and control groups and to find those compounds whose liver levels differed significantly between the two groups.ResultsDistinct clustering was observed between the ALF and control mice. Fifty-eight endogenous metabolites were identified. Compared with the control mice, many metabolites, including sugars, amino acids, fatty acids, and organic acids, underwent significant changes in the ALF group, some of which differed from changes observed in plasma. Significant reduction of some important intermediate metabolites indicates that production of ketone bodies, the tricarboxylic acid and urea cycles, gluconeogenesis, glycolysis and pentose phosphate pathways are inhibited after GalN/LPS administration.ConclusionsGC/TOFMS can be a powerful technique to perform metabonomic studies of liver tissue. GalN/LPS treatment can severely disturb substance metabolism in the liver, with different effects on metabolites compared with those observed in the plasma.

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

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

Differentiation of methoxybenzoylpiperazines (OMeBzPs) and methylenedioxybenzylpiperazines (MDBPs) By GC‐IRD and GC‐MS

The designer drug 3,4-methylenedioxybenzylpiperazine (3,4-MDBP), its positional isomer 2,3-methylenedioxybenzylpiperazine (2,3-MDBP) and three regioisomeric ring-substituted methoxybenzoylpiperazines (OMeBzPs) have identical elemental composition and no marked differences in their mass spectra with only the three methoxybenzoylpiperazine regioisomers showing one unique major fragment ion at m/z 152. Perfluoroacylation of the secondary amine nitrogen of these isomeric piperazines gave mass spectra with differences in the relative abundance of some fragment ions but did not alter the fragmentation pathway to provide unique ions for discrimination among these isomers. Exact mass determination using gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) did not provide any discrimination among these compounds since the main fragment ions are of identical elemental composition. Gas chromatography coupled to infrared detection (GC-IRD) provides direct confirmatory data for the identification of the carbonyl containing compounds and the differentiation of the psychoactive designer drug 3,4-MDBP from its direct (2,3-MDBP) and indirect (OMeBzPs) regioisomers. The mass spectra in combination with the vapour phase infrared spectra provide for specific confirmation of each of the isomeric piperazines. The underivatized and perfluoroacyl derivative forms of the five piperazines involved in this study were resolved on a stationary phase of 100% trifluoropropyl methyl polysiloxane (Rtx-200).

Dynamic Lipidomic Insights into the Adaptive Responses ofSaccharomyces cerevisiaeto the Repeated Vacuum Fermentation

Vacuum fermentation is utilized in a wide range of life science industries and biomedical R&D. Little is known, however, on the effects of the vacuum on the yeast, and in particular, on the yeast lipidome that plays a central role in maintaining cell membrane and other vital (yeast) cell functions. The present study evaluated the adaptive responses of Saccharomyces cerevisiae to repeated vacuum fermentation by lipidomic analysis. We employed gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) and liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI/MS(n)) to quantify a total of 13 intermediate sterols and 139 phospholipid species of yeast cells. Principal components analysis found that the PI (phosphatidylinositol) 26:0, PI 28:0, PE (phosphatidylethanolamine) 32:1, and PE 34:1 were potential biomarkers to distinguish the vacuum fermentation process. Quantitative analysis showed that vacuum fermentation increased the synthesis of PI and the PC (phosphatidylcholine) species with short saturated acyl chains. The synthesis of PC via CDP-choline and turnover of PC were enhanced, instead of formation via methylation of PE. Additionally, increased PI at the expense of PE and PG (phosphatidylglycerol) was associated with enhancement of ethanol productivity. Vacuum fermentation caused eburicol accumulation, suggesting that vacuum can activate the branch of the ergosterol biosynthesis pathway. Eburicol decrease and PI increase contributed to recovery of cellular activities with oxygenating treatment. Ethanol productivity was increased by sixfold in vacuum-treated cells. These observations may allow the development of future mechanistic approaches to optimization of yeast fermentation under vacuum for bioindustry and life science applications. In particular, our findings on changes in lipid molecular species and the ergosterol biosynthesis pathway elucidate the defense responses of yeast cell membranes during the repeated vacuum fermentation, which by extension, provided an important lead insight on how best to protect the cell membranes from the extreme long-term stress conditions.

Metabolomics unravel contrasting effects of biodiversity on the performance of individual plant species.

In spite of evidence for positive diversity-productivity relationships increasing plant diversity has highly variable effects on the performance of individual plant species, but the mechanisms behind these differential responses are far from being understood. To gain deeper insights into the physiological responses of individual plant species to increasing plant diversity we performed systematic untargeted metabolite profiling on a number of herbs derived from a grassland biodiversity experiment (Jena Experiment). The Jena Experiment comprises plots of varying species number (1, 2, 4, 8, 16 and 60) and number and composition of functional groups (1 to 4; grasses, legumes, tall herbs, small herbs). In this study the metabolomes of two tall-growing herbs (legume: Medicago x varia; non-legume: Knautia arvensis) and three small-growing herbs (legume: Lotus corniculatus; non-legumes: Bellis perennis, Leontodon autumnalis) in plant communities of increasing diversity were analyzed. For metabolite profiling we combined gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) and UPLC coupled to FT-ICR-MS (LC-FT-MS) analyses from the same sample. This resulted in several thousands of detected m/z-features. ANOVA and multivariate statistical analysis revealed 139 significantly changed metabolites (30 by GC-TOF-MS and 109 by LC-FT-MS). The small-statured plants L. autumnalis, B. perennis and L. corniculatus showed metabolic response signatures to increasing plant diversity and species richness in contrast to tall-statured plants. Key-metabolites indicated C- and N-limitation for the non-leguminous small-statured species B. perennis and L. autumnalis, while the metabolic signature of the small-statured legume L. corniculatus indicated facilitation by other legumes. Thus, metabolomic analysis provided evidence for negative effects of resource competition on the investigated small-statured herbs that might mechanistically explain their decreasing performance with increasing plant diversity. In contrast, taller species often becoming dominant in mixed plant communities did not show modified metabolite profiles in response to altered resource availability with increasing plant diversity. Taken together, our study demonstrates that metabolite profiling is a strong diagnostic tool to assess individual metabolic phenotypes in response to plant diversity and ecophysiological adjustment.

Impact of Genetics and Environment on the Metabolite Composition of Maize Grain

This study sought to assess genetic and environmental impacts on the metabolite composition of maize grain. Gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) measured 119 identified metabolites including free amino acids, free fatty acids, sugars, organic acids, and other small molecules in a range of hybrids derived from 48 inbred lines crossed against two different tester lines (from the C103 and Iodent heterotic groups) and grown at three locations in Iowa. It was reasoned that expanded metabolite coverage would contribute to a comprehensive evaluation of the grain metabolome, its degree of variability, and, in principle, its relationship to other compositional and agronomic features. The metabolic profiling results established that the small molecule metabolite pool is highly dependent on genotypic variation and that levels of certain metabolite classes may have an inverse genotypic relationship to each other. Different metabolic phenotypes were clearly associated with the two distinct tester populations. Overall, grain from the C103 lines contained higher levels of free fatty acids and organic acids, whereas grain from the Iodent lines were associated with higher levels of amino acids and carbohydrates. In addition, the fold-range of genotype mean values [composed of six samples each (two tester crosses per inbred x three field sites)] for identified metabolites ranged from approximately 1.5- to 93-fold. Interestingly, some grain metabolites showed a non-normal distribution over the entire corn population, which could, at least in part, be attributed to large differences in metabolite values within specific inbred crosses relative to other inbred sets. This study suggests a potential role for metabolic profiling in assisting the process of selecting elite germplasm in biotechnology development, or marker-assisted breeding.

Thermal degradation comparison of polypropylene glycol and its complex with β-cyclodextrin

In this paper, the difference in thermal degradation behavior between polypropylene glycol (PPG) and its complex of β-cyclodextrin was carefully compared by a gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) as well as in situ Fourier transformation infrared spectroscopy and thermogravimetric (TG) analyses. The present data revealed a very interesting phenomenon that there was a variation in the order of thermal stability of PPG and its complex between the conditions of TG and GC-TOF-MS. In addition, the relative abundances of released fragments in the inclusion complex were changed with different programmed temperatures in GC-TOF-MS measurements. We believe that this work will provide a better understanding on the degradation behavior of polypseudorotaxanes. Graphical abstract: [Display omitted] .

Study on thermal decomposition behavior of survived β-cyclodextrin in its inclusion complex of clove oil by nonisothermal thermogravimetry and gas chromatography coupled to time-of-flight mass spectrometry analyses

The thermal decomposition behavior of survived β-cyclodextrin in its inclusion complex of clove oil is investigated by nonisothermal thermogravimetry (TG) analysis at the heating rates of 5.0, 10.0, 15.0, 20.0 and 25.0 K min −1. The TG profiles based on mass loss as a function of temperature show a clear trend of increased thermal decomposition temperature with increased heating rate. Gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) with a programmed temperature heating treatment is performed to experimentally investigate the relationship between procedural decomposition temperature and fragment composition of the sample. The results on the basis of fragment analysis explain the different mass loss of the sample corresponding to different temperatures on the gradient hot stage.

A comparative study of amino acid measurement in leaf extracts by gas chromatography-time of flight-mass spectrometry and high performance liquid chromatography with fluorescence detection

Gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) has become a promising technique for simultaneous and rapid analysis of small metabolites in complex mixtures. The aim of this work was to establish the quantitative nature of the information generated by amino acid analysis of crude leaf extracts using GC-TOF-MS. Dried aliquots of methanol/water extracts of Arabidopsis leaves were analysed in parallel by GC-TOF-MS following trimethylsilylation or high performance liquid chromatography and fluorescence detection of o-phthaldialdehyde derivatives (OPA-HPLC). Twenty amino acids could be routinely detected in leaf extracts by both methods. Because of instability of some trimethylsilylated derivatives, all GC-TOF-MS analyses were performed within a window of 2 h 30 min following derivatization. Repeatability studies showed that relative standard deviations for multiple injections of a single extract were below 20% for both techniques, though significantly smaller for OPA-HPLC. Similar between-extract variability and condition-independent biological variation were detected by OPA-HPLC and GC-TOF-MS, and both techniques detected similar environmentally induced changes in four major amino acids. Recovery of standard compounds through the extraction procedure was between 80% and 120% for OPA-HPLC but more variable when analysed by GC-TOF-MS. When quantified on the basis of tissue fresh weight according to response factors of mixed standards, the two techniques gave consistent values for a number of amino acids but divergent values for others. Taken together, the results suggest GC-TOF-MS analysis of Arabidopsis leaves with the present protocol can be used for absolute quantification of 4–7 amino acids, accurate relative quantification of 8–11 amino acids, and more limited quantification for five compounds of this class.

Determination of organophosphorus fire retardants and plasticizers in wastewater samples using MAE-SPME with GC-ICPMS and GC-TOFMS detection

Determination of organophosphorus fire retardants and plasticizers at trace levels in wastewater is described. In this work, microwave assisted extraction (MAE) and solid-phase microextraction (SPME) are used for sample preparation to extract and preconcentrate the analytes, followed by analysis by gas chromatography coupled to inductively coupled plasma mass spectrometry (GC-ICP-MS) for phosphorus-specific detection. Gas chromatography coupled to time of flight mass spectrometry (GC-TOF-MS) was used to confirm the organphosphorus fire retardants in wastewater. The detection limits of organophosphorus fire retardants (OPFRs) were 29 ng L(-1) for tri-n-butyl phosphate (TnBP), 45 ng for L(-1) for tris(2-butoxyethyl)phosphate (TBEP), and 50 ng L(-1) for tris(2-ethylhexyl)phosphate (TEHP). Optimized extraction conditions were performed at 65 degrees C for 30 min and with 10% NaCl. Application of MAE during the sample preparation prior to the SPME allowed the detection of tris(2-ethylhexyl) phosphate, which has been difficult to determine in previous work. Application of the method to wastewater samples resulted in detecting 3.1 microg L(-1) P from TnBP, 5.0 microg L(-1) P from TBEP, and 4.0 microg L(-1) P from TEHP. The presence of these compounds were also confirmed by SPME-GC-TOF-MS.