Headspace Volatile Organic Compound Research Articles

Comparative analysis of defensive secondary metabolites in wild teosinte and cultivated maize under flooding and herbivory stress.

Climate change is driving an alarming increase in the frequency and intensity of abiotic and biotic stress factors, negatively impacting plant development and agricultural productivity. To survive, plants respond by inducing changes in below and aboveground metabolism with concomitant alterations in defensive secondary metabolites. While plant responses to the isolated stresses of flooding and insect herbivory have been extensively studied, much less is known about their response in combination. Wild relatives of cultivated plants with robust stress tolerance traits provide an excellent system for comparing how diverse plant species respond to combinatorial stress, and provide insight into potential germplasms for stress-tolerant hybrids. In this study, we compared the below and aboveground changes in the secondary metabolites of maize (Zea mays) and a flood-tolerant wild relative Nicaraguan teosinte (Zea nicaraguensis) in response to flooding, insect herbivory, and their combination. Root tissue was analyzed for changes in belowground metabolism. Leaf total phenolic content and headspace volatile organic compound emission were analyzed for changes in aboveground secondary metabolism. Results revealed significant differences in the root metabolome profiles of teosinte and maize. Notably, the accumulation of the flavonoids apigenin, naringenin, and luteolin during flooding and herbivory differentiated teosinte from maize. Aboveground, terpenes, including trans-α-bergamotene and (E)-4,8-dimethylnona-1,3,7-triene, shaped compositional differences in their volatile profiles between flooding, herbivory, and their combination. Taken together, these results suggest teosinte may be more tolerant than maize due to dynamic metabolic changes during flooding and herbivory that help relieve stress and influence plant-insect interactions.

Headspace Volatile Organic Compound Profiling of Pleural Mesothelioma and Lung Cancer Cell Lines as Translational Bridge for Breath Research.

IntroductionMalignant pleural mesothelioma (MPM) is a lethal cancer for which early-stage diagnosis remains a major challenge. Volatile organic compounds (VOCs) in breath proved to be potential biomarkers for MPM diagnosis, but translational studies are needed to elucidate which VOCs originate from the tumor itself and thus are specifically related to MPM cell metabolism.MethodsAn in vitro model was set-up to characterize the headspace VOC profiles of six MPM and two lung cancer cell lines using thermal desorption-gas chromatography-mass spectrometry. A comparative analysis was carried out to identify VOCs that could discriminate between MPM and lung cancer, as well as between the histological subtypes within MPM (epithelioid, sarcomatoid and biphasic).ResultsVOC profiles were identified capable of distinguishing MPM (subtypes) and lung cancer cells with high accuracy. Alkanes, aldehydes, ketones and alcohols represented many of the discriminating VOCs. Discrepancies with clinical findings were observed, supporting the need for studies examining breath and tumor cells of the same patients and studying metabolization and kinetics of in vitro discovered VOCs in a clinical setting.ConclusionWhile the relationship between in vitro and in vivo VOCs is yet to be established, both could complement each other in generating a clinically useful breath model for MPM.

Discrimination of French wine brandy origin by PTR-MS headspace analysis using ethanol ionization and sensory assessment.

The headspace volatile organic compound (VOC) fingerprints (volatilome) of French wine brandies were investigated by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS). Protonated ethanol chemical ionization was used with dedicated experimental conditions that were previously validated for model wines. These included a reference vial containing a hydro-alcoholic solution with the same ethanol content (20% v/v) as the diluted sample spirits, which was used to establish steady-state ionization conditions. A low electric field strength to number density ratio E/N (85 Td) was used in the drift tube in order to limit the fragmentation of the protonated analytes. The obtained headspace fingerprints were used to investigate the origin of French brandies produced within a limited geographic production area. Brandies of two different vintages (one freshly distilled and one aged for 14years in French oak barrels) were successfully classified according to their growth areas using unsupervised (principal component analysis, PCA) and supervised (partial least squares regression discriminant analysis, PLS-DA) multivariate analyses. The models obtained by PLS-DA allowed the identification of discriminant volatile compounds that were mainly characterised as key aroma compounds of wine brandies. The discrimination was supported by sensory evaluation conducted with free sorting tasks. The results showed that this ethanol ionization method was suitable for direct headspace analysis of brandies. They also demonstrated its ability to distinguish French brandies according to their growth areas, and this effect on brandy VOC composition was confirmed at a perceptive level.

Changes in volatile organic compounds in the headspace of modified atmosphere packed and unpacked white sausages

Abstract White sausage has a complex volatile organic compound (VOC) profile, attributed to meat and to the mixture of ingredients (i.e. spices, onion and parsley). Modifications of this profile can be associated with changes in the sensory characteristics of the product, i.e. chemical reactions or bacterial spoilage. The aim of this study was, for the first time, to characterize and compare the VOC headspace profiles of white sausages stored in modified atmosphere conditions at 4 °C for up to 22 d. Headspace VOCs of sausages were analyzed in closed packages and immediately after opening of the packages. VOCs profiles included 5 alcohols, 4 esters, 4 ketones, 14 monoterpenes, 14 sulfur-containing compounds, and 5 miscellaneous compounds. The emission of all alcohols, important for sensory perception, increased while that of the majority of components attributed to spices and parsley was constant during storage. Emission of sulfur-containing compounds significantly differed between packed and unpacked sausages. Methyl thiolacetate, propyl thiolacetate and dimethyl trisulfide, associated with spoilage, were increasingly emitted after day 16. Exact knowledge of the VOCs profile and prevention of the accumulation of undesired VOCs is essential for further optimization of sausage packaging.

Effective preconcentration of volatile organic compounds from aqueous solutions with polydimethylsiloxane-coated filter paper

This study explored a click method of using filter paper (FP) and a polydimethylsiloxane (PDMS) polymer coating solution to prepare a cost-effective volatile organic compound (VOC) preconcentrating sampler. This is the first report of successfully cross-linking a hydrophobic polymer with cellulose in filter paper via a sol-gel method and its application to the preconcentration of headspace VOCs. Our Fourier transform infrared spectroscopy analysis results of the PDMS-coated filter paper (FP-PDMS) showed that the spectral intensity of the alcoholic OH stretch from FP or PDMS was reduced by the addition of trifluoroacetic acid to the PDMS solution, which indicated that an alcohol group in PDMS underwent cross-linking with another alcohol group in the cellulose or PDMS. Scanning electron microscopy (SEM) images of FP-PDMS revealed that the fibrous structure of the FP surface was partially compromised by the PDMS coating, but the porous structure of FP is partially preserved. The addition of the PDMS coating to the FP increased the efficiency of the preconcentration of headspace VOCs evaporated from water. Three types of carbon additives, activated carbon, graphite, and fullerene, were tested in order to evaluate their effects on headspace VOC preconcentration efficiency for FP-PDMS, with the addition of activated carbon found to provide the largest increase in preconcentration efficiency. The extent of the enhancement of the preconcentration efficiency provided by the carbon additives varied with the VOC compounds, as well the type of carbon additive. The FP-PDMS both with and without activated carbon can be used to successfully preconcentrate benzene, toluene, ethylbenzene, and m-xylene from sub-ppb water samples with the headspace gas sampling method.

Application of Electronic-Nose Technologies and VOC-Biomarkers for the Noninvasive Early Diagnosis of Gastrointestinal Diseases †.

Conventional methods utilized for clinical diagnosis of gastrointestinal (GI) diseases have employed invasive medical procedures that cause stress, anxiety and pain to patients. These methods are often expensive, time-consuming, and require sophisticated chemical-analysis instruments and advanced modeling procedures to achieve diagnostic interpretations. This paper reviews recent applications of simpler, electronic-nose (e-nose) devices for the noninvasive early diagnosis of a wide range of GI diseases by collective analysis of headspace volatile organic compound (VOC)-metabolites from clinical samples to produce disease-specific aroma signatures (VOC profiles). A different “metabolomics” approach to GI disease diagnostics, involving identifications and quantifications of disease VOC-metabolites, are compared to the electronic-nose approach based on diagnostic costs, accuracy, advantages and disadvantages. The importance of changes in gut microbiome composition that result from disease are discussed relative to effects on disease detection. A new diagnostic approach, which combines the use of e-nose instruments for early rapid prophylactic disease-screenings with targeted identification of known disease biomarkers, is proposed to yield cheaper, quicker and more dependable diagnostic results. Some priority future research needs and coordination for bringing e-nose instruments into routine clinical practice are summarized.

Versatile set-up for non-invasive in vitro analysis of headspace VOCs

Volatile organic compound (VOC) profiles emitted in trace concentrations from bacteria or cells has gained increasing importance over the decades. Analysis of VOCs in the headspace does not interfere with in vitro systems and, therefore, offers new options for non-invasive monitoring of cultures. Currently there is not any available standardized in vitro sampling system which considers effects of dilution and contamination onto ppbV to pptV VOC concentrations during. In this study a new in vitro system for online and offline headspace measurement of biological cultures was designed. The system was built from inert materials, equipped with universal sampling ports and easily adjustable volume options. Standard VOC mixtures in the system were analyzed by means of proton-transfer-reaction time-of-flight mass spectrometry and needle-trap-microextraction coupled with gas chromatography/mass spectrometry with a variance of 5%–14% and 10%–15%, respectively. In a proof of concept setup volatile emissions over cell cultures and pure media were assessed. The newly developed system enabled reliable and reproducible headspace analyses of in vitro cultures. As parallel application of different analytical methods is possible and confounding factors could be minimized, this set-up represents an important step towards standardization of headspace analysis over biological cultures.

Rapid total volatile organic carbon quantification from microbial fermentation using a platinum catalyst and proton transfer reaction-mass spectrometry.

A novel analytical system was developed to rapidly and accurately quantify total volatile organic compound (VOC) production from microbial reactor systems using a platinum catalyst and a sensitive CO2 detector. This system allows nearly instantaneous determination of total VOC production by utilizing a platinum catalyst to completely and quantitatively oxidize headspace VOCs to CO2 in coordination with a CO2 detector. Measurement of respiratory CO2 by bypassing the catalyst allowed the total VOC content to be determined from the difference in the two signals. To the best of our knowledge, this is the first instance of a platinum catalyst and CO2 detector being used to quantify the total VOCs produced by a complex bioreactor system. Continuous recording of these CO2 data provided a record of respiration and total VOC production throughout the experiments. Proton transfer reaction-mass spectrometry (PTR-MS) was used to identify and quantify major VOCs. The sum of the individual compounds measured by PTR-MS can be compared to the total VOCs quantified by the platinum catalyst to identify potential differences in detection, identification and calibration. PTR-MS measurements accounted on average for 94 % of the total VOC carbon detected by the platinum catalyst and CO2 detector. In a model system, a VOC producing endophytic fungus Nodulisporium isolate TI-13 was grown in a solid state reactor utilizing the agricultural byproduct beet pulp as a substrate. Temporal changes in production of major volatile compounds (ethanol, methanol, acetaldehyde, terpenes, and terpenoids) were quantified by PTR-MS and compared to the total VOC measurements taken with the platinum catalyst and CO2 detector. This analytical system provided fast, consistent data for evaluating VOC production in the nonhomogeneous solid state reactor system.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-016-0264-2) contains supplementary material, which is available to authorized users.

Mo1664 Clostridium Difficile Detection by Fecal Headspace Volatile Organic Compound Analysis with an Electronic-Nose Device is Best Suited for Point-of-Care Testing Due to Time-Dependent Factors

Mo1664 Clostridium Difficile Detection by Fecal Headspace Volatile Organic Compound Analysis with an Electronic-Nose Device is Best Suited for Point-of-Care Testing Due to Time-Dependent Factors

Discrimination of Three Panax Species Based on Differences in Volatile Organic Compounds Using a Static Headspace GC-MS-Based Metabolomics Approach.

Panax ginseng (Asian ginseng), Panax quinquefolium (American ginseng) and Panax notoginseng (notoginseng) are highly valuable tonic herbs derived from the Panax genus that have similar morphological appearances and odors but different pharmacological activities and clinical indications. Thus, the authentication of these three Panax species is crucial for ensuring the quality, safety and efficacy of medication. In the present study, a static headspace gas chromatography - mass spectrometry (GC-MS) followed by a multivariate statistical analysis was developed to globally characterize the volatile organic compound (VOC) profiles in P. ginseng, P. quinquefolium, and P. notoginseng, and subsequently to discover differentiating chemical markers. Under the optimized conditions, the headspace VOCs of a total of 49 batches of Panax herbs derived from the three Panax species were profiled, and the dataset of sample code, [Formula: see text]-m/z pair and ion intensity was processed by unsupervised principal component analysis (PCA) and by supervised partial least squared discriminant analysis (PLS-DA) to comprehensively compare the chemical differences in Panax across the species. The results demonstrated that Panax herbs derived from three species possess obviously diverse chemical characteristics of VOCs, PCA, and PLS-DA. According to their VOC profiles, 49 tested samples could be clearly differentiated according to species. Chemomarker 1, 2, and 4 might be used as unique chemical markers of P. ginseng, P. notoginseng and P. quinquefolium, respectively. Our findings indicate that static headspace GC-MS-based VOC profiling, combined with multivariate statistical analysis, provide a reliable tool to discriminate between the three Panax species and to identify their differentiation markers, which will be helpful for ensuring their quality, safety and efficacy.

Volatile emanations from in vitro airway cells infected with human rhinovirus

Respiratory viral infections such as human rhinovirus (HRV) can lead to substantial morbidity and mortality, especially in people with underlying lung diseases such as asthma and COPD. One proposed strategy to detect viral infections non-invasively is by volatile organic compound (VOC) assessment via analysis of exhaled breath. The epithelial cells are one of the most important cell lines affected during respiratory infections as they are the first line of pathogen defense. Efforts to discover infection-specific biomarkers can be significantly aided by understanding the VOC emanations of respiratory epithelial cells. Here we test the hypothesis that VOCs obtained from the headspace of respiratory cell culture will differentiate healthy cells from those infected with HRV. Primary human tracheobronchial cells were cultured and placed in a system designed to trap headspace VOCs. HRV-infected cells were compared to uninfected control cells. In addition, cells treated with heat-killed HRV and poly(I:C), a TLR3 agonist, were compared to controls. The headspace was sampled with solid-phase microextraction fibers and VOCs were analyzed by gas chromatography/mass spectrometry. We determined differential expression of compounds such as aliphatic alcohols, branched hydrocarbons, and dimethyl sulfide by the infected cells, VOCs previously associated with oxidative stress and bacterial infection. We saw no major differences between the killed-HRV, poly(I:C), and control cell VOCs. We postulate that these compounds may serve as biomarkers of HRV infection, and that the production of VOCs is not due to TLR3 stimulation but does require active viral replication. Our novel approach may be used for the in vitro study of other important respiratory viruses, and ultimately it may aid in identifying VOC biomarkers of viral infection for point-of-care diagnostics.

Indoor VOCs From Household Floor Dust: Comparison of Headspace with Desorbed VOCs; Method for VOC Release Determination

One hundred and eighty eight Volatile organic compound (VOCs) were identified from dust emission, dust headspace, and in air sampling in a residence by sampling on Tenax TA followed by thermal desorption and HRGC/MS. Of these, 83 compounds were found in dust headspace. Aliphatic aldehydes (C4-8 and octane were major contributors to headspace gas chromatograms while the total ion current response for desorbed VOCs (120° C) was dominated by n-alkanes (C7-16), n- and branched alkanals (C4-10 and alkanoic acids (C2-14). Many of the identified VOCs could be products of microbial or human metabolism. Dust volatiles resulting from desorption were compared w dust headspace VOC analyses and found to be comparable considering the temperature difference. A method for determination of total VOC (TVOC-dust) emission at 120°C, was developed. Variation in desorption TVOC analyses was mainly due to sample heterogeneity.