Dynamic Headspace Research Articles

Analysis of potential cyanide antidote, dimethyl trisulfide, in whole blood by dynamic headspace gas chromatography–mass spectroscopy

Cyanide is a rapidly acting and highly toxic chemical. It inhibits cytochrome c oxidase in the mitochondrial electron transport chain, resulting in cellular hypoxia, cytotoxic anoxia and potentially death. In order to overcome challenges associated with current cyanide antidotes, dimethyl trisulfide (DMTS), which converts cyanide to less toxic thiocyanate in vivo, has gained much attention recently as a promising next-generation cyanide antidote. While there are three analysis methods available for DMTS, they each have significant disadvantages. Hence, in this study, a dynamic headspace (DHS) gas chromatography–mass spectroscopy method was developed for the analysis of DMTS from rabbit whole blood. The method is extremely simple, involving only acidification of a blood sample, addition of an internal standard (DMTS-d6) and DHS-GC–MS analysis. The method produced a limit of detection of 0.04 μM for DMTS with dynamic range from 0.2 to 50 μM. Inter- and intraassay accuracy (100 ± 15% and 100 ± 9%, respectively), and precision (<10% and <9% relative standard deviation, respectively) were good. The validated method performed well during pharmacokinetic analysis of DMTS from the blood of rats treated with DMTS, producing excellent pharmacokinetic parameters for the treatment of cyanide exposure. The method produced significant advantages over current methods for analysis of DMTS and should be considered as a “gold standard” method for further development of DMTS as a potential next-generation cyanide countermeasure.

Losing a Scent of One’s Self: Is There a Reduction in Floral Scent Emission in Self-Pollinating Phlox cuspidata versus Outcrossing Phlox drummondii?

Premise of research. Studies of the evolution of self-pollination have generally predicted reductions in pollinator-attractive morphological floral traits over time as a result of relaxed pollinator-mediated selection and/or positive selection associated with improved self-pollination. Nonmorphological traits, such as floral scent, may also become reduced in self-pollinating taxa due to relaxed pollinator-mediated selection. However, evidence of such reductions in floral scent of selfing versus outcrossing taxa is limited. We explored this possibility in the scent of the predominantly selfing taxa Phlox cuspidata and its close outcrossing relative Phlox drummondii.Methodology. Scent was collected and analyzed from four populations of each plant species using dynamic headspace extraction and gas chromatography-mass spectroscopy. Scent emission rates were compared between species and among populations nested within species via MANOVA.Pivotal results. Of the 37 scent variables examined, only three showed significant differences between species. However, all three were emitted in decreased quantities from selfing P. cuspidata.Conclusions. While our findings provide some support for reductions of scent emission in selfing versus outcrossing annual Phlox, the retention of substantial scent production by P. cuspidata suggests continued dependence on pollinators (for either outcrossing or facultative selfing). This is further supported by maintenance of a pollen-ovule ratio similar to outcrossing P. drummondii. The retention of significant terpenoid emission alternatively indicates potential defensive functions for floral scent, as these compounds are known to have antiherbivore and antipathogen properties. Future research should examine both possibilities.

Developing Multi Stimuli‐Responsive Core/Shell Microcapsules to Control the Release of Volatile Compounds

AbstractEncapsulation of 2‐oxoacetates into poly(urea‐urethane) core/shell microcapsules allows the light‐induced controlled release of volatile compounds such as fragrances, plant volatiles, pheromones, or other semiochemicals. On exposure to UVA light, 2‐oxoacetates decompose to form a carbonyl compound together with CO2or CO, which can build overpressure inside the capsules that expands and/or cleaves the capsule wall to release its content. The influence of the structure and ratio of the polyisocyanates and diamines used for interfacial polymerization, as well as the composition of the capsule wall and the oil phase, are investigated by dynamic headspace analysis of the released volatile compounds to optimize the performance of the delivery system. The combination of a light‐induced release with the mechanical cleavage of the capsule gives access to multi stimuli‐responsive systems that selectively respond to the different triggers applied. Furthermore, the concept outlined in the present work is generally applicable to other photolabile precursors that generate a gas inside the capsules and thus release co‐encapsulated active molecules as a direct response to light.

Identification of Odor-Active Compounds Released from a Damaged Plant of the Asian Skunk Cabbage Symplocarpus renifolius.

Symplocarpus renifolius (Asian skunk cabbage) is a perennial herb of the Araceae family. As its common name implies, this plant produces a strong garliclike irritant odor with a rotten note when the plant parts are crushed. To elucidate the odor characteristics, the volatile compounds released from crushed plant parts (rhizome, petioles, and leaf blades) of S. renifolius were identified by a dynamic headspace method. Fifteen sulfur compounds were identified as odor-active compounds by gas chromatography-mass spectrometry-olfactometry (GC-MS-O). The sulfur compounds may be responsible for the strong odor emitted by crushed skunk cabbage. Many of the compounds lack a carbon-carbon bond, and all of the carbon atoms are connected to sulfur. This is regarded as the characteristic structure of the sulfur compounds released from the damaged plant parts of the skunk cabbage. Nine of the sulfur compounds were detected in all three of the plant parts analyzed in this study: hydrogen sulfide, methanethiol, 1-hexanethiol, methyl dithioformate, 2,4-dithiapentane, dimethyl trisulfide, methional, 2,3,5-trithiahexane, and tris(methylthio)methane. Methyl dithioformate and methylthiomethyl dithioformate were identified for the first time as natural products.

Floral scent in a sexually deceptive Ophrys orchid: from headspace collections to solvent extractions

ABSTRACTSexually deceptive orchid flowers use visual, tactile and olfactory cues of female insects in order to attract males of one or a few closely related species as pollinators. Ophrys L. is the most species-rich genus of sexually deceptive orchids in the Mediterranean Basin. Despite Ophrys pollinated by Andrena male bees use alkanes and mainly alkenes with specific double-bond positions as key signals that trigger pseudocopulatory behavior, some volatile organic compounds (VOCs) with low molecular weight were found as long-range attractants non-eliciting copulatory behavior. Since floral scents in Ophrys have been extensively studied by solvent extractions here we aimed to understand which floral volatiles are found when two different collection methods are used in Ophrys panormitana flowers. By knowing their chemical composition, we could better understand the scent chemistry of this Ophrys species without overlooking VOCs which could also have a function in its pollination biology.Scent samples collected by dynamic headspace and by solvent extraction were analyzed by gas chromatography/mass spectrometry (GC/MS).The floral scent of O. panormitana is composed by a bouquet of VOCs with lower and higher molecular weights. The headspace samples contained VOCs with higher volatility (mainly one aliphatic alcohol and two aliphatic ketones) whereas the solvent extracts were composed by VOCs with lower volatility (exclusively long-chain alkanes and alkenes). Overlapping in VOCs between headspace and solvent samples were not found. For the first time Andrena nigroaenea was observed during the pseudocopulation and removing the pollinaria of a flower of O. panormitana.Abbreviations: VOCs, volatile organic compounds; GC/MS, gas chromatography-mass spectrometry; KRI, Kovats Retention Indices

Methyl halide production by cultures of marine thraustochytrids, Aurantiochytrium sp., Botryochytrium radiatum, and Schizochytrium sp.

The oceans are an important source of the methyl halides released into the atmosphere and impacting the stratospheric ozone layer. Marine bacteria such as Erythrobacter and Pseudomonas are known to be sources of methyl halides in marine environments, but the production of methyl halides by thraustochytrids, the other decomposers in the marine ecosystem, have not been studied. Here, we report the productions of three methyl halides, CH3Cl, CH3Br, and CH3I, in cultures of thraustochytrids. Thraustochytrids were incubated at 20 °C, 25 °C, and 30 °C, and the concentrations of methyl halides in the gas phase above these cultures were determined using dynamic headspace gas chromatography–mass spectrometry. Growth of thraustochytrids was monitored by measuring optical density at 600 nm during the culture period. Cell density was also measured for some samples of thraustochytrids by counting with a plankton-counting chamber during the culture period. Three of the four tested strains of marine thraustochytrids were found to produce methyl halides in culture: Botryochytrium radiatum produced CH3Cl and CH3I while Aurantiochytrium sp. and Schizochytrium sp. produced CH3Br. Increases of CH3Cl, CH3Br, and CH3I concentrations were observed during the exponential-growth phase in all cultures of the three thraustochytrids, except for the 30 °C culture of B. radiatum. The maximum concentration for CH3Cl production by a thraustochytrid (B. radiatum) was increased as the culture temperature increased from 20 °C to 30 °C; the maximum concentrations of CH3Cl in the cultures incubated at 20 °C, 25 °C, and 30 °C were about 6000, 9600 and 14,000 pmol L−1, respectively. However, the maximum concentrations for the CH3I production of thraustochytrid (B. radiatum) decreased when the temperature was increased from 20 °C to 30 °C. To the best of our knowledge, this is the first report of methyl halide production by heterotrophic thraustochytrids. Our results suggest that thraustochytrids may be a source of methyl halides in marine environments.

Floral scent in Iris planifolia (Iridaceae) suggests food reward

Iris species can adopt different pollination strategies to attract their pollinators, generalized shelter-mimicking, specialized deceptive sexual-mimicking or food-rewarding. As attractive stimuli, Iris flowers may use their colours, large-size, symmetry, and volatile organic compounds (VOCs). However, relatively few studies investigated Iris floral olfactory cues in the context of plant-visitor/pollinator interactions. In the present study we combined the identification of the floral volatiles of the nectariferous I. planifolia with insects visiting its flowers to gather data on its biology. Floral volatiles were collected in the natural environment by dynamic headspace and analysed by gas chromatography-mass spectrometry (GC-MS). Insect visitors/pollinators were also recorded. The volatile bouquet was aromatic-dominated with 1,4 dimethoxybenzene as major compound. Among the insects visiting its flowers, bumble and honey bees were the most abundant followed by hover flies. Overall, our results suggest that I. planifolia advertises its food reward by an aromatic dominated volatile composition.

Emission analysis of recycled tire rubber modified asphalt in hot and warm mix conditions.

The hazardous emissions of crumb rubber (CR) modified asphalt during construction has been a concern for a long period. This study aims to identify the emission components in the CR modified asphalt in traditional hot mix asphalt (HMA) and with recently developed warm mix asphalt (WMA). The dynamic headspace gas chromatography-mass spectrometry (GCMS) was employed for identifying the emission of asphalt binders at 120°C, 140°C and 160°C. The coupling of gas chromatography and Fourier-transform infrared spectroscopy (GC-FTIR) was used to analyze the emission during the plant mixing for conventional HMA, CR-HMA and CR-WMA. The results showed the emission amount was highly dependent on mixing temperature. The warm mix technology can reduce the emission level significantly and should be encouraged in the asphalt mixture containing CR. Asphalt source and other extra additives in producing CR modified asphalt can also affect the emission significantly. Asphalt mixture containing CR can release toxic emissions such as xylene and toluene significantly higher compared to that without CR. In addition, it was found that the emission amount from the GCMS test for asphalt binder was lower than that in the field test for asphalt mix due to the thin asphalt film of asphalt mix.

Compositional changes of the floral scent volatile emissions from Asian skunk cabbage (Symplocarpus renifolius, Araceae) over flowering sex phases.

Flowering of the Asian skunk cabbage (Symplocarpus renifolius, Araceae) shows a sequential expression of female, bisexual and male sex phases. The protogynous thermogenic inflorescence has unpleasant odours, but the contributing chemical composition is poorly understood. To determine the volatile composition of odour emissions from each S. renifolius flowering phase. The dynamic headspace method was used to collect floral volatiles from six intact S. renifolius inflorescences in their natural habitat. Collected volatiles from the three flowering phases were analysed using gas chromatography-mass spectrometry/olfactometry (GC-MS/O). Female-phase inflorescences were characterised by an earthy-rotten-minty odour, while male-phase inflorescences typically exhibited a rotten-oily odour. Approximately 160 compounds were detected in volatiles from the three phases. Common to all phases were 3-methylbutyl 3-methylbutanoate, 1,8-cineole, dimethyl disulphide and sabinene, together accounting for 52 to 54% of total volatiles. GC-MS/O revealed that at least 28 volatiles including eight S-containing compounds contributed to the unpleasant odour of S. renifolius. Among them, dimethyl disulphide (onion-like), methional (potato-like), and the tentatively identified methyl dithioformate (garlic-like) were intense odour-active compounds in each floral phase. Additionally, 2-isopropyl-3-methoxypyrazine (IPMP) was a major contributor to the earthy odour that was characteristic of the female phase. No marked changes were observed in floral volatile compositions over the three flowering phases of S. renifolius. Instead, flower phase-dependent proportional changes of minor components (e.g. IPMP and 2,3-butanedione) altered the odour characteristics between the female and male phases.

Improved analysis of propylene oxide, propylene chlorohydrin and propylene bromohydrin: Presentation

The benefits and deficiencies of several methods of analysis for PPO and PXH, including the aqueous extraction used in ASTA method 23.1 and the MTBE extraction method previously reported by the authors, will be discussed. Novel methods utilizing dynamic headspace extraction and solid phase microextraction (SPME) will also be reported with particular emphasis on preventing artefactual effects. Preliminary experiments have found that dynamic headspace sampling can lower detection limits by up to 3 orders of magnitude.

Floral Scents inPachira aquatica(Malvaceae): A Species with Diverse Floral Visitors in a Mexican Lowland Forests

The chemical composition of the floral scent released by Pachira aquatica was analyzed in situ using standard dynamic headspace and Gas Chromatography-Mass Spectroscopy. A total of 34 compounds were found in the scent, 31 of which were identified and classified as terpenoids, benzenoids, fatty acid derivatives or nitrogen containing compounds. The predominant compounds emitted are trans-β-ocimene (51.74 %), ( Z)-3-hexenyl acetate (7.96 %), one of the unknown compounds (7.44 %), pentyl butanoate (7.02 %), trans-caryophyllene (4.49 %), methyl salicylate (3.49 %) and methyl benzoate (2.26 %).

Developing a Method for the Collection and Analysis of Burnt Remains for the Detection and Identification of Ignitable Liquid Residues Using Body Bags, Dynamic Headspace Sampling, and TD-GC×GC-TOFMS

In cases of suspected arson, a body may be intentionally burnt to cause loss of life, dispose of remains, or conceal identification. A primary focus of a fire investigation, particularly involving human remains, is to establish the cause of the fire; this often includes the forensic analysis of fire debris for the detection of ignitable liquid residues (ILRs). Commercial containers for the collection of fire debris evidence include metal cans, glass jars, and polymer/nylon bags of limited size. This presents a complication in cases where the fire debris consists of an intact, or partially intact, human cadaver. This study proposed the use of a body bag as an alternative sampling container. A method was developed and tested for the collection and analysis of ILRs from burnt porcine remains contained within a body bag using dynamic headspace sampling (using an Easy-VOC™ hand-held manually operated grab-sampler and stainless steel sorbent tubes containing Tenax TA) followed by thermal desorption comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry (TD-GC×GC-TOFMS). The results demonstrated that a body bag containing remains burnt with gasoline tested positive for the presence of gasoline, while blank body bag controls and a body bag containing remains burnt without gasoline tested negative. The proposed method permits the collection of headspace samples from burnt remains before the remains are removed from the crime scene, limiting the potential for contamination and the loss of volatiles during transit and storage.

Optimization and validation of a DHS-TD-GC-MS method to wineomics studies

A dynamic headspace sorptive extraction (DHS) combined with thermal desorption (TD) and coupled with gas chromatography-mass spectrometry (GC/MS) was developed for the determination of forty-four volatile aroma metabolites (VAMs) which describe aroma fingerprints of wines. The response surface methodology (RSM) and a central composite design (CCD) was used to obtain the optimal values for the experimental extraction variables, and the results were assessed by an analysis of variance (ANOVA) and a principal component analysis (PCA). The VAMs exhibited optimal extraction with the high levels of salt concentration (1.5 g NaCl) and using an extraction temperature of 40 °C during 10 min, and a subsequent purge volume of 300 mL. Subsequently, the calibration curves were created for the quantification of each VAMs with seven levels of concentration obtaining a correlation coefficients (R2) above 0.9900 for all of them. The proposed method was successfully validated and showed good precision and accuracy values for all VAMs. Lastly, the method was applied to quantify VAMs, responsible for the aroma fingerprints of white and red wines, from different Denomination of Origin

High correlation between octanol-air partition coefficient and aroma release rate from O/W emulsions under non-equilibrium

Aroma release kinetics determines the palatability of food consumed by humans. Therefore, to estimate release behaviors of aroma compounds is important. We investigated the relationship between the rates of the release of aroma compounds from food matrices and octanol-water, octanol-air, and water-air partition coefficients. The aroma compounds used were limonene, ethyl hexanoate, 2-methylpyrazine, nonanal, benzaldehyde, ethyl benzoate, α-terpineol, geraniol, benzyl alcohol, and octanoic acid. The rates of their release from oil-in-water (O/W) emulsions were measured under non-equilibrium conditions using a purge-and-trap dynamic headspace extraction system. The results indicated that the octanol-air partition coefficients correlated better with the logarithms of the aroma compound release rates than either the octanol-water or the water-air partition coefficients. Furthermore, this correlation was independent of the oil volume ratios in the O/W emulsions. Our findings therefore suggest that octanol-air partition coefficients can be used to predict the release rates of aroma compounds from O/W emulsions.

Olive oil quality classification and measurement of its organoleptic attributes by untargeted GC–MS and multivariate statistical-based approach

The capabilities of dynamic headspace entrainment followed by thermal desorption in combination with gas chromatography (GC) coupled to single quadrupole mass spectrometry (MS) have been tested for the determination of volatile components of olive oil. This technique has shown a great potential for olive oil quality classification by using an untargeted approach. The data processing strategy consisted of three different steps: component detection from GC–MS data using novel data treatment software PARADISe, a multivariate analysis using EZ-Info, and the creation of the statistical models. The great number of compounds determined enabled not only the development of a quality classification method as a complementary tool to the official established method “PANEL TEST” but also a correlation between these compounds and different types of defect. Classification method was finally validated using blind samples. An accuracy of 85% in oil classification was obtained, with 100% of extra virgin samples correctly classified.

Sexual and temporal variations in floral scent in the subdioecious shrub Eurya japonica Thunb.

In many flowering plants, floral scents are a significant trait for visitors, playing an important role in attracting pollinators and/or detracting herbivores. The evolution of flowering plants from hermaphroditism to dioecy is often accompanied by sexual dimorphism in floral scent. In this study, floral scents emitted by different sexual morphs of the subdioecious shrub Eurya japonica Thunb. were collected using a dynamic headspace method, and sexual and temporal variations were evaluated by gas chromatography–mass spectrometry (GC–MS). Two volatiles, α‐pinene and linalool, were identified as the major components of floral scents in females, hermaphrodites, and males. The males emit higher amounts of floral scents, particularly α‐pinene, compared to females or hermaphrodites. Floral scents emitted by males generally decrease as flowers enter senescence, whereas those from females or hermaphrodites do not significantly differ. Intraspecific variations in floral scents of subdioecious species provided by this study would contribute to better understanding of sexual dimorphism in floral scent.

Incomplete synchrony of inflorescence scent and temperature patterns in Arum maculatum L. (Araceae)

In many Araceae both scent and heat production are known to temporally vary throughout anthesis, and in several species strong scents are released for pollinator attraction when thermogenesis is also strong. However, it is not known whether the temporal patterns of both scent emission and temperature are strictly synchronous and, for example, reach their maxima at the same time. We studied Arum maculatum, a brood-site deceptive species attracting its moth fly pollinators with strong fetid scents, to study temporal patterns in scent emission and temperature during anthesis. Inflorescence scents were collected and analysed by dynamic headspace and gas chromatography-mass spectrometry (GC-MS) or by proton-transfer-reaction-time-of-flight mass spectrometry (PTR-TOFMS), and the temperature of the appendix, which is the heating osmophore during pollinator attraction, was recorded by a thermocouple. We overall found that scent emission and temperature patterns were strongly correlated. However, in none of the seven studied individuals was the highest amount of scent released at times with the maximum temperature difference. Thus, patterns of scent emission and temperature are somewhat asynchronous suggesting that high scent emission rates and temporal scent patterns in plants with thermogenesis cannot be solely explained by temperature patterns. This calls for more in-depth studies to better understand the interplay between scent emission and thermogenesis.

Contribution of headspace to the analysis of cyclodextrin inclusion complexes

Headspace technology is a sampling method of a gas, which has been previously in contact with a liquid or a solid matrix from which volatiles were released into the gaseous phase. It is generally coupled to a subsequent gas chromatography analysis. The headspace analysis can be carried out either as a one-step extraction (static or equilibrium headspace) or as a continuous extraction (dynamic headspace). The static headspace gas chromatography (SH-GC) is gaining an increasing interest for the study of cyclodextrin (CD) inclusion complexes with volatile compounds. CDs are natural supermolecular hosts able to encapsulate volatile compounds and improve their functionalities (e.g. solubility, stability, retention, controlled release). Herein, the application of the SH-GC in the CD field will be reviewed. This paper will focus on the characterization of the inclusion complexes via the SH-GC, mainly aiming at the determination of formation constant (Kf) and encapsulation efficiency (EE%) values. Moreover, it will review the application of the SH-GC to monitor the properties of volatile compounds upon encapsulation (e.g. retention, controlled release).

Lipid Oxidation and Degradation Products in Raw Materials: Low‐Fat Topical Skin‐Care Formulations

AbstractTopical skin formulations with a lipid content below 15% were stored for 6 months at 5, 20, or 40 °C or for 2 weeks at 50 °C in darkness or at 20 °C with exposure to light for 6 months. The volatile lipid‐oxidation compounds formed during this storage period were compared to those formed in the raw materials during 3 months of accelerated stability storage at 40 °C. The volatile compounds were collected by dynamic headspace and analyzed using gas chromatography–mass spectrometry. It was possible to link eight out of nine volatile compounds detected during storage of topical skin formulations to the raw materials. In addition, a possible link between the appearance of butane nitrile and the decomposition of an initiator used for polyacrylate crosspolymer‐6 production was observed. The polymer may originate from texture modifiers added to the topical skin formulation or from plastics used for packaging of topical skin formulations. Furthermore, six well‐known lipid‐oxidation and nonenzymatic browning products were suggested to originate from the two raw materials, tricaprylin/tricaprin and coconut oil.

Identification of Floral Fragrances and Analysis of Fragrance Patterns in Herbaceous Peony Cultivars

Thirty herbaceous peony (section Paeonia of the genus Paeonia) cultivars were divided into four groups (no fragrance, light fragrance, medium fragrance, or intense fragrance) based on their sensory evaluation scores. Using dynamic headspace sampling (DHS) and automatic thermal desorption–gas chromatography/mass spectrometry (ATD-GC/MS), 130 volatile organic components were detected in these 30 cultivars and a total of 72 compounds were identified as scent components. The main compounds were phenylethyl alcohol, β-caryophyllene, linalool, (R)-citronellol, and nerol. Selecting α-pinene as the standard, the volatile components of these cultivars were quantitatively analyzed. By combining the sensory evaluation scores and the results of quantitative analysis, we found that ‘Going Bananas’, ‘Cream Delight’, ‘Zhu Sha Pan’, ‘Qiao Ling’, ‘Duchess de Nemours’, and ‘Yang Fei Chu Yu’ displayed an intense fragrance and, thus, had relatively high commercial value for the flower fragrance industry. ‘Red Magic’, ‘Joker’, ‘Fairy Princess’, ‘Lovely Rose’, ‘Carina’, and ‘Etched Salmon’ were excluded from the hierarchical cluster of aromatic compounds and the analysis of fragrance patterns because of the low amount of fragrance they released and poor sensory evaluation results. Based on a cluster analysis, assessment of the major aromatic compounds, and the results of sensory evaluation, the remaining 24 cultivars were divided into five fragrance patterns for the first time: woody scent [cluster I (major fragrance β-caryophyllene)], fruity scent [cluster II (phenylethyl alcohol)], lily scent [cluster III (linalool)], rose scent {cluster IV [(R)-citronellol]}, and an orange blossom scent [cluster V (nerol)].