Dynamic Headspace Gas Chromatography Research Articles

Temporal, Developmental, and Comparative Characterization of the Floral Volatile Emissions of the Famously Scented Violet Species, Viola odorata

Violets (Viola) are potential candidates for aroma-focused breeding research. Though most Viola species and modern hybrids lack fragrance, the genus contains a famously scented species, Viola odorata L. This species and its cultivars are genetic resources of aroma traits that could be used to investigate the selection for and transmission of fragrance during the breeding process. Despite its famous scent, however, the floral volatile emissions of V. odorata have not been characterized using modern headspace techniques. Using static and dynamic headspace volatile collection methods and gas chromatography–mass spectrometry, the floral volatile emissions of V. odorata were temporally and developmentally characterized. Floral volatiles were also sampled from 10 V. odorata cultivars, three Parma violet cultivars, five violet species, and one hybrid, and variation in scent among these violets was investigated. Total volatile emissions in V. odorata were highest from 0600 HR to 1900 HR, suggesting a diurnal pattern of emission. Volatile emissions also varied over the developmental lifespan of the flower, with the highest emission of individual and total volatiles occurring, in general, from stages 0 or +1 to stages +3 or +4. Floral scent qualitatively and quantitatively differed among assorted violets. The floral volatile emissions of V. odorata exhibit temporal and developmental variation. Compared with the other violet species in this study, sweet violets are intensely fragrant. The quantity and quality of floral scent differs among V. odorata cultivars, providing genetic variation from which selections could be made in a fragrance-focused breeding program.

Study on the flavor of brown milk fermented by Lactobacillus paracasei K56 in different strain states

A comprehensive investigation of the differences in flavor profiles among different strains of fermented brown milk (FBM) is important to guide the improvement of the flavor quality of FBM. Seven samples were analyzed by dynamic headspace extraction (DHS) and gas chromatography–olfactometry–mass spectrometry (GC–O–MS), and a total of 73 odor compounds were identified. Key odor compounds including 3-methyl-1-butanol, ethyl acetate, linalool, furfuryl alcohol, 2-pentylfuran, hexanal, and 1-octen-3-ol, were screened by multivariate statistical analysis to reveal the flavor differences of FBM from different strains. 3-Methyl-1-butanol and ethyl acetate were found to be the key odor compounds distinguishing FBM by strain K56 from other strains, and the fermentation strains were found to be the key factors affecting the flavor of FBM compared to the fermentation substrate and fermentation process. This study provided a relatively systematic investigation of the flavor of FBM and could be used to monitor changes in odor components and sensory characteristics for product quality control.

Spoilage markers for freshwater fish: A comprehensive workflow for non-targeted analysis of VOCs using DHS-GC-HRMS

Changes of volatile organic compounds (VOCs) patterns during 6 days of storage at +4 °C were investigated in different freshwater fish species, namely carp and trout, using dynamic headspace gas chromatography time-of-flight mass spectrometry (DHS-GC-TOFMS). DHS parameters were systematically optimized to establish optimum extraction and pre-concentration of VOCs. Moreover, different sample preparation methods were tested: mincing with a manual meat grinder, as well as mincing plus homogenization with a handheld homogenizer both without and with water addition. The addition of water during sample preparation led to pronounced changes of the volatile profiles, depending on the molecular structure and lipophilicity of the analytes, resulting in losses of up to 98 % of more lipophilic compounds (logP > 3).The optimized method was applied to trout and carp. Trout samples of different storage days were compared using univariate (Mann-Whitney U test, fold change calculation) and multivariate (OPLS-DA) statistics. 37 potential spoilage markers were selected; for 11 compounds identity could be confirmed via measurement of authentic standards and 10 compounds were identified by library spectrum match. 22 compounds were also found to be statistically significant spoilage markers in carp. Merging results of the different statistical approaches, the list of 37 compounds could be narrowed down to the 14 most suitable for trout spoilage assessment.This study comprises a systematic evaluation of the capabilities of DHS-GC coupled to high-resolution (HR) MS for studying spoilage in different freshwater fish species, including a comprehensive data evaluation workflow.

Floral scent chemistry of sympatric species of Philodendron (Araceae) sharing a common pollinator in the fragmented coastal Atlantic Forest of southeastern Brazil

Floral volatiles are crucial components in flower advertisement, often contributing to the reproductive isolation of angiosperms through scent-mediated differential pollinator attraction. Recently, there were significant advances in our understanding of the chemical communication between plants and cyclocephaline beetles, a predominant group of Neotropical pollinators. However, details on how the floral scent chemistry differs or converges among species pollinated by different or the same cyclocephaline beetle species are still unknown. Here, we used dynamic headspace sampling and gas chromatography coupled with mass spectrometry to investigate the floral fragrance chemistry of eight co-flowering Philodendron (Araceae) species that share a single pollinator, Cyclocephala variolosa (Melolonthidae, Cyclocephalini). Additionally, we compared our results to published data on the floral fragrances of different conspecifics pollinated by other species of cyclocephaline beetles. Although all the investigated Philodendron spp. emitted perceivably intense floral scents, the number of volatile organic compounds in the analyzed samples varied between 1 and 50 among species. Also, the overall relative scent composition strongly differed among species (or chemotypes). The floral scents of four of the investigated species (P. appendiculatum, P. cordatum, P. crassinervium, and P. eximium) and one of the two chemotypes of P. corcovadense were dominated by (Z)-jasmone (46 to 100% total relative concentration). High relative amounts of (Z)-2-pentenyl acetate (44 to 66%) characterized the samples of P. undulatum and Philodendron bipinnatifidum, while (E)-4,8-dimethyl-1,3,7-nonatriene was the main constituent in samples of P. curvilobium (75%) and the other P. corcovadense chemotype (56%). The scents of Philodendron spp. pollinated by C. variolosa differed from those of conspecifics associated with other cyclocephaline beetle species, but we also verified significant interspecific variation among these species sharing a common pollinator. We hypothesize that this community of co-flowering plants might be reproductively isolated despite being pollinated by the same pollinator species and having partly overlapping scent compositions.

Scented at day and night: diel variation in the floral scent chemistry of the threatened tree Amburana cearensis (Leguminosae) and effects of this variation on its pollinators

The reproductive success of most angiosperms depends on pollinators. A combination of floral traits, including olfactory cues, are involved in attracting these animals. The emission and chemical composition of floral volatile organic compounds (VOCs) is often associated with the sensory preferences of the most frequent floral visitors. However, the relationship between VOCs and nocturnal and diurnal pollinators is poorly known in tropical dry forests. Our study describes the dynamics of floral scent chemistry throughout the anthesis of Amburana cearensis (Leguminosae) and its association with floral visitors in the Caatinga dry forest, one of the largest expanses of seasonally dry tropical forest (SDTF) in the world. The species is a threatened tree with high socioeconomic importance in the Caatinga and other SDTFs of South America (exploited for timber and medicinal uses). Its flowers emit an intense, pleasant and sweet fragrance throughout anthesis, starting at ∼16:00 h and ending at ∼15:00 h of the following day (lasting 23 h). We used dynamic headspace sampling and gas chromatography coupled with mass spectrometry (GC-MS) to collect and analyze the floral scent within a natural population. The fragrance of A. cearensis was characterized by the dominant presence of monoterpenes, especially linalool and (Z)-linalool oxide (furanoid) and (Z)-linalool oxide (pyranoid), as well as (E,E)-α-farnesene and an aromatic benzenoid, benzyl alcohol. The relative proportions of floral VOCs emitted by A. cearensis changed during anthesis, with a marked presence of linalool in daytime samples (day: 45% / night: 27%) and furanoid (Z)-linalool oxide at night (day: 12% / night: 29%). The dominance of benzyl alcohol, linalool and its oxides in the floral scent of A. cearensis is possibly related to the attraction of nocturnal and diurnal Lepidoptera as pollen vectors. Indeed, we observed six species of butterflies and seven species of moths pollinating the flowers of A. cearensis in 41 h of observations. However, other terpenoids in the fragrant blend possibly contribute to the attraction of additional diurnal floral visitors, including bees, which are also effective pollinators. The continuous scent production throughout anthesis, and the changes in floral scent with a peak of linalool production during the day, may be related to the wide spectrum of pollinators of A. cearensis. This association between floral visitors and dynamics of VOCs presentation may therefore increase the reproductive success of the species, which only blooms every two years and is strictly self-incompatible.

Chemical Attraction of Gall Midge Pollinators (Cecidomyiidae: Cecidomyiinae) to Anthurium acutangulum (Araceae)

Flowering plants often use chemical signals to attract their pollinators, and compounds that elicit attraction are known for several groups of pollinators. For other pollinators such as gall midges, however, compounds responsible for their attraction to flowers are largely unknown. Here, we describe the pollination biology of Anthurium acutangulum, a Neotropical aroid species found to be attractive to gall midges. We collected and analyzed its floral scent by dynamic headspace collections and gas chromatography coupled to mass spectrometry, and identified compounds responsible for pollinator attraction. The inflorescences were almost exclusively visited by gall midges (females; Cecidomyiidae: Cecidomyiinae) and released a strong scent reminiscent of freshly cut cucumber, mainly (5S,7S)-trans-conophthorin, (E2,Z6)-2,6-nonadienal, and cis-conophthorin. Behavioral assays with the two most abundant compounds identified (E2,Z6)-2,6-nonadienal as being highly attractive to the female gall midge pollinators, whereas (5S,7S)-trans-conophthorin was not attractive. Overall, we introduce a new specialized gall midge pollination system and identify the chemical mediating communication between the pollinators and their host plants.

Floral scent is different between sexual phases within individuals in a synchronously dichogamous shrub (Canella winterana) but there is no distinct female or male scent profile across individuals

Floral scent is a highly complex and variable floral characteristic that is involved in pollinator attraction. One possible cause for variation in floral scent can be sexual identity of the flower. Here, we examine the floral scent bouquet of a synchronously dichogamous shrub, Canella winterana (L.) Gaertn.We used dynamic headspace extraction and gas chromatography – mass spectroscopy, followed by statistical analysis using non-metric multidimensional scaling, SIMPER, MANOVA, and PERMANOVA to identify and compare the scent profiles of Canella winterana in its female and male phase for multiple individuals as well as multiple inflorescences of a single tree over one cycle of its entire sexual phase transition. The scent profile of C. winterana is composed of 49 volatile organic compounds and dominated by five compounds. We found no evidence for distinct male or female scent profiles; however, there were significant differences in scent emission between different sexes within some individuals. Two compounds explained over half of the variation between sexual stages within individuals. Our exploration of a single tree's sexual phase transition, including neuter phase, found that five compounds dominated the female phase scent bouquet and that female phase was distinct from male and neuter phase. This study offers new insight into the role that variability in floral scent between sexual phases might play in variable pollinator behavioral responses. These results suggest partial support for two distinct hypotheses regarding the differences between the sex phases (1) honest signaling and (2) sexual mimicry.

Biopesticide Trunk Injection Into Apple Trees: A Proof of Concept for the Systemic Movement of Mint and Cinnamon Essential Oils.

The use of conventional pesticides is debated because of their multiple potential adverse effects on non-target organisms, human health, pest resistance development and environmental contaminations. In this setting, this study focused on developing alternatives, such as trunk-injected essential oil (EO)-based biopesticides. We analysed the ecophysiology of apple trees (Malus domestica) following the injection of Cinnamomum cassia and Mentha spicata nanoemulsions in the tree’s vascular system. Targeted and untargeted volatile organic compounds (VOCs) analyses were performed on leaf-contained and leaf-emitted VOCs and analysed through dynamic headspace–gas chromatography–mass spectrometry (DHS-GC-MS) and thermal desorption unit (TDU)-GC-MS. Our results showed that carvone, as a major constituent of the M. spicata EO, was contained in the leaves (mean concentrations ranging from 3.39 to 19.7 ng gDW–1) and emitted at a constant rate of approximately 0.2 ng gDW–1 h–1. Trans-cinnamaldehyde, C. cassia’s major component, accumulated in the leaves (mean concentrations of 83.46 and 350.54 ng gDW–1) without being emitted. Furthermore, our results highlighted the increase in various VOCs following EO injection, both in terms of leaf-contained VOCs, such as methyl salicylate, and in terms of leaf-emitted VOCs, such as caryophyllene. Principal component analysis (PCA) highlighted differences in terms of VOC profiles. In addition, an analysis of similarity (ANOSIM) and permutational multivariate analysis of variance (PERMANOVA) revealed that the VOC profiles were significantly impacted by the treatment. Maximum yields of photosystem II (Fv/Fm) were within the range of 0.80–0.85, indicating that the trees remained healthy throughout the experiment. Our targeted analysis demonstrated the systemic translocation of EOs through the plant’s vascular system. The untargeted analysis, on the other hand, highlighted the potential systemic acquired resistance (SAR) induction by these EOs. Lastly, C. cassia and M. spicata EOs did not appear phytotoxic to the treated trees, as demonstrated through chlorophyll fluorescence measurements. Hence, this work can be seen as a proof of concept for the use of trunk-injected EOs given the systemic translocation, increased production and release of biogenic VOCs (BVOCs) and absence of phytotoxicity. Further works should focus on the ecological impact of such treatments in orchards, as well as apple quality and production yields.

Analysis of the Soil Fumigant, Dimethyl Disulfide, in Swine Blood by Dynamic Headspace Gas Chromatography–Mass Spectroscopy

Plant parasites and soilborne pathogens directly reduce the overall yield of crops, vegetables, and fruits, negatively impacting the market demand for these products and their net profitability. While preplant soil fumigation helps maintain the consistent production quality of high-value cash crops, most soil fumigants are toxic to off-target species, including humans. Dimethyl disulfide (DMDS) has recently been introduced as a relatively low toxicity soil fumigant. Although DMDS exhibits low toxicity compared to other soil fumigants, it is volatile and exposure can cause eye, nasal, and upper respiratory tract irritation, skin irritation, nausea, dizziness, headache, and fatigue. While there is one analysis method available for DMDS from biological matrices, it has significant disadvantages. Hence, in this study, a dynamic headspace gas chromatography–mass spectroscopy (DHS-GC-MS) method was developed for the analysis of DMDS in swine whole blood. This method is highly sensitive and requires only three steps: 1) acid denaturation, 2) addition of internal standard, and 3) DHS-GC-MS analysis. The method produced a wide linear range from 0.1 – 200 µM with an excellent limit of detection of 30 nM. Intra- and interassay accuracy (100±14% and 100±11%, respectively) and precision (<5% and <6% relative standard deviation, respectively) were also excellent. The method worked well to quantify the DMDS levels in the blood of dimethyl trisulfide (DMTS)-treated swine (i.e., DMDS is a byproduct of DMTS treatment) with no interfering substances at or around the retention time of DMDS (i.e., 2.7 min). This simple, rapid, and extremely sensitive method can be used for the quantification of DMDS levels in blood to verify exposure to DMDS or to monitor levels of DMDS following DMTS treatment (e.g., for cyanide poisoning).

Egg yolk phospholipids: a functional food material to generate deep-fat frying odorants.

Phospholipids are an important precursor for the generation of carbonyl compounds that play a significant role in the characteristic aroma of deep-fat fried foods. Phospholipids extracted from hen egg yolks were added into sunflower oil (2.0g kg-1 ) and heated with or without chicken meat at 160 °C for 10min, and then dynamic headspace extraction and gas chromatography-mass spectrometry were used to extract and analyse the volatiles. The results showed that the characteristic deep-fat frying odorants, such as (E,E)-2,4-decadienal and (E,Z)-2,4-decadienal, as well as 1-octen-3-one, (E)-2-nonenal, octanal, methional, dimethyl disulfide and alkylpyrazines, had increased by 3-65 times in the sunflower oil with added phospholipids, and increased up to six times in chicken meat that had been treated with phospholipids prior to heating. There is potential for the food industry to use low levels of phospholipids, particularly egg yolk phospholipids, to increase deep-fat frying odorants in a wide range of deep-fried products. © 2019 Society of Chemical Industry.

Simultaneous determination of aromatic and chlorinated compounds in urine of exposed workers by dynamic headspace and gas chromatography coupled to mass spectrometry (dHS-GC–MS)

Mixed exposure to chemical products is a topical issue for occupational health and often includes exposure to volatile organic compounds (VOCs). As very few methods are available for evaluating these mixed exposures, the aim of this work was to develop a simple biomonitoring method to assess simultaneous occupational exposures to chlorinated and aromatic VOCs by analyzing the unmetabolized fraction of the VOCs in the urine of workers.Volatile organic compounds were analyzed using dynamic headspace gas chromatography coupled to mass spectrometry (dHS-GC–MS), and 11 unmetabolized urinary VOCs were measured into headspace phase, without any time-consuming pretreatment. Simultaneously, a standardized collection protocol was designed to avoid VOC losses or the contamination of urinary samples. The calibration samples were real urines, spiked with known amounts of the VOC mixtures studied. Test investigations were performed on potentially exposed workers in three factories in order to assess the effectiveness of both the collection protocol and analytical method.A satisfactory level of sensitivity was achieved, with limits of quantification (LOQ) between 10 and 15 ng/L obtained for all VOCs (except for styrene at 50 ng/L). Calibration curves were linear in the 0–20 μg/L range tested, with R2 correlation coefficients of 0.991 to 0.998. At the lowest concentration tested (0.08 μg/L), within-day precision varied from 2.1 to 5.5% and between-day precision ranged from 2.7 to 8.5%.Sample stability at −20 °C required that urinary samples be analyzed within 3 months. Even though the urinary concentrations of VOCs used in the plants were mostly quite low, significant differences between post-shift and pre-shift were observed.In conclusion, a fast, sensitive, specific and easy-to-use method has been developed for extracting VOCs from human urine using dHS-GC–MS. The method described has proven to be reliable for assessing current occupational exposure to chlorinated and aromatic VOCs in France.

Is old stuff back? A fatal case of ethyl chloride sniffing

BackgroundEthyl chloride (EC) or chloroethane is a colourless halogenated hydrocarbon gas regularly employed as a topical anaesthetic spray for pain-related injuries and muscle spasm in athletes. However, EC became also popular as a street drug in the 1980s. Brief inhalations of EC vapour can result in dizziness, euphoria, confusion, incoordination, hallucinosis, impairment of short-term memory and narcosis. Inhalation of higher doses, usually employed to “get high”, may be related to severe depression of the central nervous system. Indeed, toxicity and deaths have been reported so far.Case presentationA 40-year-old man was found unresponsive after EC inhalation. EC determination was performed by dynamic headspace gas chromatography coupled to mass spectrometry. EC was detected in the peripheral blood (0.156 g/L), central blood concentration (0.203 g/L) and the lung and brain (19 and 25 mg/kg). EC in the vitreous humour showed a sensitively lower respect to blood (0.018 vs 0.203 g/L).ConclusionsConsidering the results of toxicological analyses of investigations on the death scene besides the absence of any signs of trauma, death was attributed to inhalation of ethyl chloride.

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.

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.

Variation in floral characters, particularly floral scent, in sapromyophilous Stemona species.

Flowers or inflorescences often deploy various signals, including visual, olfactory, and gustatory cues, that can be detected by their pollinators. In many plants, these cues and their functions are poorly understood. Deciphering the interactions between floral cues and pollinators is crucial for analyzing the reproductive success of flowering plants. In this study, we examined the composition of the fetid floral scents produced by several Stemona species, including nine S. tuberosa populations from across China, using dynamic headspace adsorption, gas chromatography, and mass spectrometry techniques. We compared variations in floral phenotype, including floral longevity, nectar rewards, pollinator behavior, and flower length and color among the Stemona species. Of the 54 scent compounds identified, the major compounds include fetid dimethyl disulfide, dimethyl trisulfide, 1-pyrroline, butyric acid, p-cresol, isoamyl alcohol, and indole. We detected striking differentiation in floral scent at both the species and population level, and even within a population of plants with different colored flowers. Floral characteristics related to sapromyophily and deceptive pollination, including flower color mimicking livor mortis and a lack of nectar, were found in five Stemona species, indicating that Stemona is a typical sapromyophilous taxon. Species of this monocot genus might employ evolutionary tactics to exploit saprophilous flies for pollination.

Effect of temperature on the production rates of methyl halides in cultures of marine proteobacteria

Abstract Methyl halides released from the ocean serve as important carriers of halogen into the atmosphere. The transported halogens are released into the atmosphere through photolysis, and catalyze ozone depletion. Marine bacteria are known to be a source of methyl halides in marine environments, but the effects of environmental temperature on the production of methyl halides by bacteria have not been studied. Here, we examined the effect of temperature on methyl halide production in a culture of marine bacteria (HKF-1) belonging to Erythrobacter , which was incubated for several days at 15 °C, 20 °C, 25 °C, or 30 °C. We also analyzed the effect of temperature on the production of methyl halides in a culture of the marine γ -proteobacterium Pseudomonas stutzeri . The concentrations of methyl halides such as CH 3 Cl, CH 3 Br, and CH 3 I in the gas phase above cultured samples were determined using dynamic headspace gas chromatography–mass spectrometry. Bacterial growth was monitored by measuring the optical density at 600 nm. The production rate of CH 3 Cl by marine bacteria (HKF-1) was increased with increasing temperature from 15 °C to 30 °C, and the maximum production rate for CH 3 Cl was ~ 19 pmol (10 9 cells) − 1 d − 1 at 30 °C, which was about 26 times higher than that at 15 °C (~ 0.7 pmol (10 9 cells) − 1 d − 1 ). The production rates of CH 3 Cl by P. stutzeri were also increased with increasing temperature from 15 °C to 30 °C. The production rates for CH 3 Br by bacteria (HKF-1) were increased with increasing temperature from 15 °C to 30 °C, whereas changes in the production rates for CH 3 I by these two bacteria were relatively small during the temperature rise from 15 °C to 30 °C. Higher production rates of CH 3 Cl, CH 3 Br, and CH 3 I were observed during the exponential phase than during the stationary phase in the cultures of HKF-1. The ratio of production rates (CH 3 Cl:CH 3 Br:CH 3 I) was 1.0:0.12:0.015 in the cultures of HKF-1, and this ratio was almost constant between 15 °C and 25 °C. These results suggested that water temperature could affect the production of methyl halides derived from bacteria and would be a significant factor for estimating the emissions of methyl halides from marine environments.

Is Prey Specificity Constrained by Geography? Semiochemically Mediated Oviposition in Rhizophagus grandis (Coleoptera: Monotomidae) with Its Specific Prey, Dendroctonus micans (Coleoptera: Curculionidae: Scolytinae), and with Exotic Dendroctonus species.

Examples of totally specific predators are rare, and the mechanisms underlying this specificity are often poorly understood. In Eurasia, the Monotomid beetle Rhizophagus grandis is found only in the galleries of its prey, the bark beetle Dendroctonus micans. The specificity of R. grandis relies on kairomones which female predators use to adjust their oviposition to the number of prey larvae available in a gallery. Yet these chemical signals are still largely unknown. The North American D. punctatus and D. valens, which are not sympatric with R. grandis but have a similar ecology as D. micans, could also elicit predator oviposition, which would suggest that specificity in this predator-prey system is constrained by geography. In order to further identify these determinants of specificity, we used artificial oviposition boxes to compare the oviposition level of R. grandis in the presence of larvae of each of the three prey species. We jointly used sequential dynamic headspace extractions and gas chromatography coupled with mass spectrometry to investigate oviposition stimuli associated with each prey species and potential oviposition inhibitors emitted by the predator. We further assessed potential stimuli with the analysis of emissions from D. micans larvae reared alone. Overall, we identified and quantified 67 compounds, mostly terpenes. Several robust candidate stimulants or inhibitors of R. grandis' oviposition were identified. The three prey species elicited similar oviposition levels in R. grandis, which suggests that this predator could form new associations outside of its native range.

Oxidative stability and microstructure of 5% fish‐oil‐enriched granola bars added natural antioxidants derived from brown alga Fucus vesiculosus

The aims of this study were to (i) investigate the ability of Icelandic brown algae Fucus vesiculosus extracts to inhibit lipid oxidation in granola bars fortified with fish oil‐in‐water emulsion; (ii) investigate whether addition of the seaweed extracts affected the physical microstructure of the oil droplets in granola bars. The oxidative stability of the bars at 20°C was evaluated over a period of 10 wk by measuring the development of peroxides and volatile compounds using dynamic headspace gas chromatography mass spectrometry (DHS GC‐MS). The physical microstructure was determined using microscopy. All extracts − except water extract in low concentration − reduced lipid oxidation during 10 wk of storage when added in a concentration of 0.5 or 1 g extract/100 g emulsion. Ethanol (EE) and acetone extracts (AE) (in the lowest concentration) were found to be most efficient as antioxidants in the bars. The antioxidant efficacy of these two extracts was among other related to an improved incorporation of the fish oil‐in‐water emulsions in the bars, high total phenolic content, high radical scavenging activity together with high interfacial affinity of phenolic compounds and probably regeneration of tocopherol.Practical applications: The work showed the application potential of F. vesiculosus extracts as a natural antioxidant in low‐moisture foods such as granola bars. These findings implied that the multi‐functional nature of these extracts provides not only oxidative stability of the food but also a physical stability.Granola bars enriched with 10% Sodium caseinate (Na‐Cas) fish oil‐in‐water emulsion where Fucus vesiculosus extracts where added as antioxidant to control lipid oxidation. Development of secondary oxidation product, 1‐penten‐3‐ol (ng/g granola bar) in the granola bars and confocal light scattering microscopic images of granola bar added 0.5 g acetone extract/100g emulsion (AE1) and the Control (Con) (without extract). The efficacy of acetone extracts to limit development of 1‐penten‐3‐ol in granola bars was found to be related to extract composition as well as the microstructure, as fish oil emulsions in the bars were more stable when this extract was added. Error bars indicate SD of the measurements (n = 3).

Validation Study of Analysis of 1-Phenyl-2-Propanone in Illicit Methamphetamine Samples by Dynamic Headspace Gas Chromatography Mass Spectrometry

A new method based on dynamic headspace sampling (DHS) coupled to GC/MS analysis was developed, optimized and validated for the analysis of 1-phenyl-2-propanone (P2P) in illicit methamphetamine (MAMP) samples. The DHS parameters were investigated to reach the sensitivity suitable for this kind of analysis. The method showed of a good specificity, linearity, accuracy, precision and robustness. The analysis of ten MAMP samples seized by the judicial authority was carried out. P2P was found in all the seizure, confirming that P2P is the starting compound of the synthesis of amphetamines.

Development of a dynamic headspace gas chromatography–mass spectrometry method for on-site analysis of sulfur mustard degradation products in sediments

Sampling teams performing work at sea in areas where chemical munitions may have been dumped require rapid and reliable analytical methods for verifying sulfur mustard leakage from suspected objects. Here we present such an on-site analysis method based on dynamic headspace GC–MS for analysis of five cyclic sulfur mustard degradation products that have previously been detected in sediments from chemical weapon dumping sites: 1,4-oxathiane, 1,3-dithiolane, 1,4-dithiane, 1,4,5-oxadithiephane, and 1,2,5-trithiephane. An experimental design involving authentic Baltic Sea sediments spiked with the target analytes was used to develop an optimized protocol for sample preparation, headspace extraction and analysis that afforded recoveries of up to 60–90%. The optimized method needs no organic solvents, uses only two grams of sediment on a dry weight basis and involves a unique sample presentation whereby sediment is spread uniformly as a thin layer inside the walls of a glass headspace vial. The method showed good linearity for analyte concentrations of 5–200ng/g dw, good repeatability, and acceptable carry-over. The method's limits of detection for spiked sediment samples ranged from 2.5 to 11μg/kg dw, with matrix interference being the main limiting factor. The instrumental detection limits were one to two orders of magnitude lower. Full-scan GC–MS analysis enabled the use of automated mass spectral deconvolution for rapid identification of target analytes. Using this approach, analytes could be identified in spiked sediment samples at concentrations down to 13–65μg/kg dw. On-site validation experiments conducted aboard the research vessel R/V Oceania demonstrated the method's practical applicability, enabling the successful identification of four cyclic sulfur mustard degradation products at concentrations of 15–308μg/kg in sediments immediately after being collected near a wreck at the Bornholm Deep dumpsite in the Baltic Sea.