Headspace Technique Research Articles

ChemInform Abstract: Plant Volatilome in Greece: A Review on the Properties, Prospects, and Chemogeography

AbstractReview: 77 refs.

Analysis of floral scent emitted from Syringa plants

Syringa is an important aromatic woody angiosperm that is widely planted in gardens. Its dry flowers are traditionally used to manufacture infusions and spices in China. In this study, the floral volatiles emitted from nine different Syringa species and varieties, viz. S. chinensis, S. p rotolaciniata, S. o blata, S. o blata var. giraldii, S. o blata var. plena, S. v ulgaris ‘Mrs Harry Bickle’, S. v ulgaris ‘Bright Centennial’, S. v ulgaris ‘White Spires’, and S. v ulgaris ‘President Lincoln’ were collected by the dynamic headspace technique, and then identified by automated thermal desorption–gas chromatography/mass spectrometry. There were significant differences in components and corresponding contents of floral scent emitted from the nine Syringa species and varieties. Among the detected components, β-ocimene exhibited the highest content, accounting for more than 70 % of the floral scent of S. p rotolaciniata, S. o blata var. giraldii, and S. v ulgaris ‘Bright Centennial’. A significant daytime variation of floral scent emitted from S. p ekinensis was recorded, especially for benzaldehyde, whose content first increased and then decreased. We studied the scent emitted from the in vitro flowers of S. v ulgaris ‘Pres Lincoln’ during the process of natural drying. Alcohol compounds were released in the greatest content, and the content of 2-ethyl-1-hexanol accounted for about 40 % of the total release amount. The results described the emission pattern and mechanisms of floral scent in Syringa.

Plant Volatilome in Greece: a Review on the Properties, Prospects, and Chemogeography.

Knowing plant volatile chemodiversity and its distribution is essential in order to study biological processes, to estimate the plants' value in use, and to establish sustainable exploitation practices. Yet, attempts to collect and assess data on scent diversity and properties in well-defined geographical areas are rare. Here, we developed a geo-referenced database of the plant volatilome in Greece by consolidating the results included in 116 research articles published in the last 25 years. The data set compiled includes 999 volatile organic compounds distributed into 178 plant taxa, 59 genera, and 19 families. Distillation is the acquisition method almost exclusively used, whereas headspace techniques that would allow the study of subtle ecological processes are generally lacking. Sesquiterpenes show the greatest richness of compounds, followed by monoterpenes and aliphatics. We assess the volatility of the compounds using the normal boiling point (nBP) as its reverse indicator, and we present the volatility spectra of the blends of the genera studied. Mean nBPs vary among genera, with maximal differences as wide as 118.4°. Finally, we feature basic chemodiversity maps for three aromatic plants, and discuss their importance and prospects as a special case of natural resources maps.

Analysis of target volatile compounds related to fishy off‐flavor in heated rapeseed oil: A comparative study of different headspace techniques

Off‐flavors, characterized by a fishy odor, are emitted during the heating of rapeseed oil in a fryer. In order to study the headspace composition of degraded rapeseed oil, and more specifically the compounds responsible for the fishy odor, four headspace techniques were evaluated: Static headspace (SHS), headspace trap (HS Trap), headspace solid phase microextraction (HS‐SPME), and headspace sorptive extraction (HSSE) coupled to gas chromatography‐mass spectrometry (GC‐MS). The selected model compounds to develop the headspace methods were 1‐penten‐3‐one, 1‐octen‐3‐one, and E,Z‐2,6‐nonadienal as known fishy odor markers. Extraction conditions for the four techniques were optimized and evaluated in terms of repeatability and sensitivity. They were then applied to the analysis of real samples of degraded rapeseed oil. SHS was not suitable for the analysis of odorant volatile compounds because of LOD values lower than those required for a quantitative analysis of the target compounds. Concerning HS‐SPME and HSSE, a discrimination against the more volatile compounds was observed. Finally, HS Trap‐GC‐MS was considered the most appropriate technique for the analysis of the headspace of rapeseed oil in this study with LOD values less than 2 μg/L for the three target compounds. More than 60 compounds were identified by HS Trap‐GC‐MS and two compounds responsible for the fishy odor could be detected. The evolution of the relative areas of these compounds was reported for fresh oil and rapeseed oil degraded by 1, 5, and 10 heating cycles.Practical applications: The characterization of the volatile compounds responsible for the fishy odor is a key industrial issue. Moreover, the developed method with HS‐Trap could be used to quantify several volatile compounds characteristic of the degradation of rapeseed oil, and to evaluate the possible effect of antioxidants on oils.Rapeseed oil is edible oil containing a substantial amount of omega 3, but the heating of this oil leads to the formation of off‐flavors, characterized by a fishy odor. The characterization of these off‐flavors is a key industrial issue, and different headspace techniques can be considered to study the molecules present in the headspace of degraded rapeseed oil.

SEASONAL VARIATION IN FLORAL SCENT OF PERSIAN MUSK ROSE (ROSA MOSCHATA HERMM.)

The seasonal variation of volatile oil compositions (VOCs) from fresh flowers of Persian Musk rose was investigated by Combi PAL Headspace Techniques. In this study, a total number of 21 VOCs were detected by headspace on the Combi PAL System and gas chromatography-mass spectrometry (HS-GC/MS) from Rosa moschata Herrm. at different seasons which was representing 92.53-99.37% of total VOCs. The analysis of VOCs at different seasons detected the major compounds: Phenyl ethyl alcohol (30.68-77.36%), 1-Nonadecene (1.01-30.42%), n-Nonadecane (4.61-14.04%), n-Heneicosane (4.47-12.07%) and 1-Tricosene (0-5.91%). Phenylpropanoids content varied significantly over time, with a low level during September and maximum content in May. In contrast to phenylpropanoids contents, the high level of fatty acid derivatives was realized during September. In all of seasons a low level of terpenoids derivatives was emitted from Persian Musk rose flowers. The results of this research suggest that the fragrance characteristics of R. moschata resulted from its specific composition and can be manipulated by seasonal changes and environmental conditions.

Development of Electronic Nose with Low-Cost Dynamic Headspace for Classifying Vegetable Oils and Animal Fats

A portable electronic nose (e-nose) using low-cost dynamic headspace and commercially metal oxide gas sensors has been developed. This paper reports evaluation on the performance of the e-nose to classify vegetable oils (sunflower and grape seed oils) and animal fats (mutton, chicken and pig fats). The e-nose consists of a dynamic headspace sampling, a gas sensor array and a real-time data acquisition system based on ATMega-16 microcontroller. The dynamic headspace can divided into two chambers, i.e. sample and gas sensor array room. It is also equipped with three small fans for adjusting sensing and purging processes. Principal component analysis (PCA) was used for measurement data analysis after all features being extracted. The first two principal components were kept because they accounted for 91.1% of the variance in the data set (first and second principals accounted for 72.9, 18.2% of the variance, respectively). This results show that the e-nose can distinguish vegetable oils and animal fats. This work demonstrates for the future that the e-nose with low-cost dynamic headspace technique may be applied to the identification of oils and fats in halal authentication.

Development and validation of an APCI-MS/GC–MS approach for the classification and prediction of Cheddar cheese maturity

Headspace techniques have been extensively employed in food analysis to measure volatile compounds, which play a central role in the perceived quality of food. In this study atmospheric pressure chemical ionisation-mass spectrometry (APCI-MS), coupled with gas chromatography–mass spectrometry (GC–MS), was used to investigate the complex mix of volatile compounds present in Cheddar cheeses of different maturity, processing and recipes to enable characterisation of the cheeses based on their ripening stages. Partial least squares-linear discriminant analysis (PLS-DA) provided a 70% success rate in correct prediction of the age of the cheeses based on their key headspace volatile profiles. In addition to predicting maturity, the analytical results coupled with chemometrics offered a rapid and detailed profiling of the volatile component of Cheddar cheeses, which could offer a new tool for quality assessment and accelerate product development.

Synthesis, characterisation and photocatalytic activity of N-doped TiO2–Nb2O5 mixed oxides

Nitrogen-doped TiO2 and TiO2–Nb2O5 catalysts were prepared by sol–gel technique using titanium isopropoxide (TIP) and potassium niobate. The obtained samples were subsequently calcined at 380 and 500°C. Undoped TiO2 and TiO2–Nb2O5 samples were also prepared by way of comparison. The photocatalytic activities of the synthesised catalysts were evaluated on the photodegradation of benzene, toluene and xylenes (BTX) solution under UVA and visible light. The level of nitrogen incorporated on N-doped TiO2–Nb2O5 catalyst was found to be 0.49 at%. Concentrations of BTX were analysed by gas chromatography applying the headspace technique. The N-doped TiO2–Nb2O5 catalyst calcined at 500°C led to reductions of benzene, toluene and xylenes greater than 65wt% after 150min of irradiation. The photocatalytic reactions followed the first order kinetics.

Volatile profile of yellow passion fruit juice by static headspace and solid phase microextraction techniques

The profile of volatile compounds of yellow passion fruit juice was analyzed by solid phase microextraction headspace (HS-SPME) and optimized static headspace (S-HS) extraction techniques. Time, temperature, NaCl concentration and sample volume headspace equilibrium parameters was adjusted to the S-HS technique. The gaseous phase in the headspace of samples was collected and injected into a gas chromatograph coupled to a mass spectrometer. In the HS-SPME technique was identified 44 volatile compounds from the yellow passion fruit juice, but with S-HS only 30 compounds were identified. Volatile esters were majority in both techniques, being identified ethyl butanoate, ethyl hexanoate, (3z)-3-hexenyl acetate, hexyl acetate, hexyl butanoate and hexyl hexanoate. Aldehydes and ketones were not identified in S-HS, but were in HS-SPME. β-Pinene, p-cymene, limonene, (Z)-β-ocimene, (E)-β-ocimene, γ-terpinene, α-terpinolene and (E) -4,8-dimethyl-1, 3,7 - nonatriene terpenes were identified in both techniques. This study showed that the S-HS optimized extraction technique was effective to recovery high concentrations of the major volatile characteristics compounds in the passion fruit, such as ethyl butanoate and ethyl hexanoate, which can be advantageous due to the simplicity of the method.

Comparison of lipids, fatty acids and volatile compounds of various kumquat species using HS/GC/MS/FID techniques

Kumquat (Fortunella spp.) is one of the important fruit species that has been introduced into Turkey recently. It is well adapted to the Mediterranean region in Turkey. Early research of kumquat was started on adaptation and pomological traits, and only a few studies have been concerned with chemical content. After understanding the health benefits of kumquat fruits farmers started their plantations in Turkey. Thus in this study the fruits of five kumquat species - Fortunella margarita (Lour.) Swingle, F. crassifolia Swingle, F. obovata Hort. ex Tanaka, F. hindsii (Champ. ex Benth.) Swingle, and limequat [Citrus aurantifolia × F. japonica (Thumb.)] - were compared based on their lipids, fatty acids and volatile profiles. The lipids, fatty acids and volatile profiles were determined by using gas chromatography with flame ionisation detection (GC/FID) and headspace gas chromatography mass spectrometry (HS-GC/MS) techniques. Volatile constituents of kumquat fruits were isolated by a headspace method. The total lipid content (%) of kumquat species ranged from 0.26% to 0.37%. The polyunsaturated fatty acids were detected in a higher amount compared to the monounsaturated fatty acids and saturated fatty acids, respectively. The headspace technique led to the identification of 39 compounds and among a total of 39 constituents identified, d-limonene was the most abundant compound, comprising 67.78-88.72%. The results indicated that kumquats are rich in dietary and health benefits. Thirty-nine compounds were identified and terpenes were the major chemical group in all kumquat genotypes. Esters, alcohols, aldehydes and ketones were also detected. The present study revealed that the kumquat fruits have a valuable levels of health beneficial chemo-preventive effects and genotypes varied based on their lipid, fatty acids and volatile constituents.

Occupational health risks among trichloroethylene-exposed workers in a clock manufacturing factory.

Trichloroethylene (TCE) is an important volatile organic compound once widely used in industry throughout the world. Occupational exposure to TCE can cause a number of health hazards such as allergic reactions and genetic damage. The purpose of this study was to evaluate occupational exposure to TCE, by analysis of the air in the breathing zone and of urine from workers employed in a clock manufacturing factory. A subjective symptom survey was conducted by using a self-administered questionnaire to evaluate the health hazards. Micronucleus (MN) frequency, based on the cytokinesis-block micronucleus assay (CBMN) in peripheral blood lymphocytes, (PBLs) was used as a biomarker for chromosome damage. A total of 244 participants, including 171 workers occupationally exposed to TCE and 73 non-exposed control employees, working mainly in office jobs in the same factory, were enrolled in this study. Analyses of airborne TCE concentrations in the workplace, and of urinary trichloroacetic acid (TCA) of the workers and controls, were performed by Gas Chromatography-Electron Capture Detector (GC-ECD) using the modified headspace technique. The average concentration of TCE in the workplace breathing zone was 27.83 ± 6.02 ppm. The average level of urinary TCA of the exposed workers and controls was 14.84 ± 1.62, 2.95 ± 0.28 mg/L. The frequency of MN/1000BN was 7.029 ± 0.39, significantly higher than for those in the control group (3.57 ± 0.31, p = 0.001). According to multiple linear regression analysis, the results indicated that urinary TCA levels correlated with the increased MN in exposed workers (r = 0.285, p < 0.001). The prevalence rate of subjective symptoms in the exposed group was 9.61-11.76 times higher than the rate of the non-exposed group (p < 0.001). It was found that skin (29.6%) and respiratory symptoms (21.1%) were the most frequent among the exposed workers.In conclusion, these results indicate that increased micronucleus frequency is associated with occupational trichloroethylene exposure. The use of TCE in the factory is threatening workers’ health.

Chemical and sensory characterisation of the aroma of Çalkarası rosé wine

Background and Aims Rosé wines play an important role in the Turkish wine industry, and among them, rosé wines made with the grape cultivar Çalkarası are the most appreciated. The aim of this work was to characterise, for the first time, the aroma of Çalkarası rosé wine. Methods and Results The aroma of a Çalkarası rosé wine from Turkey has been studied by sensory analysis, gas chromatography-olfactometry (GC-O) and four quantitative methods for the chemical analysis of volatile compounds. The aroma of the wine was dominated by fresh fruit, floral and red fruit notes. An extract obtained by a dynamic headspace technique was subjected to GC-O. The strategy allowed the odorants in the Çalkarası rosé wine to be identified and quantified. The aroma showed a complex profile with 28 compounds determined above their odour threshold. Conclusions The results correlated well with previous studies of the aroma of rosé wines. Fruity ethyl esters, β-damascenone, furaneol, fatty acids and a small amount of 3-mercapto-1-hexanol and 3-mercaptohexyl acetate all contribute to the aroma, but Çalkarası rosé wine has high level of isoamyl and 2-phenylethyl acetates, which therefore appear to be responsible for its distinctive flowery aroma. Significance of the Study This work confirms a common base of aroma compounds for rosé wines but also highlights important differences in Çalkarası wine.

Characterization of Volatiles of Necrotic Stenocereus thurberi and Opuntia littoralis and Toxicity and Olfactory Preference of Drosophila melanogster, D. mojavensis wrigleyi, and D. mojavensis sonorensis to Necrotic Cactus Volatiles

Drosophila mojavensis wrigleyi and D. mojavensis sonorensis are geographically separated races of cactophilic fruit flies. D. mojavensis sonorensis inhabits the Sonoran Desert and utilizes necrotic rots of Stenocereus thurberi Engelm. as a food source and to oviposit while D. mojavensis wrigleyi inhabits Santa Catalina Island, California and utilizes the necrotic rots of Opuntia littoralis (Engelm.) Cockerell. The objectives of this study were to determine the volatile compositions of the necrotic cacti and to determine if the volatile components show either selective toxicity or attraction toward the fruit flies. The volatile chemical compositions of field-rot specimens of both necrotic cacti were obtained by dynamic headspace (purge-and-trap) and hydrodistillation techniques and analyzed by gas chromatography - mass spectrometry. The volatile fraction of necrotic S. thurberi early rot was dominated by carboxylic acids (84.8%) and the late rot by p-cresol (32.6% in the dynamic headspace sample and 55.9% in the hydrodistilled sample). O. littoralis volatiles were dominated by carboxylic acids (86% in the dynamic headspace sample and 89.1% in the hydrodistilled sample). Fifteen compounds that were identified in the necrotic rot volatiles were used to test insecticidal activity and olfactory preference on the cactophilic Drosophila species, as well as D. melanogaster. Differences in toxicity and olfactory preference were observed between the different taxa. Both races of D. mojavensis exhibited toxicity to benzaldehyde and 2-nonanone, while butanoic acid and palmitic acid were tolerated at high concentrations. D. m. wrigleyi demonstrated a greater olfactory preference for anisole, butanoic acid, 2-heptanone, and palmitic acid than did D. m. sonorensis, while D. m. sonorensis demonstrated a greater preference for hexadecane, octanoic acid, and oleic acid than did D. m. wrigleyi.

Coupled Extraction and Dynamic Headspace Techniques for the Characterization of Essential Oil and Aroma Fingerprint of Thymus Species

Natural essential oils and extracts were obtained from three different Thymus species (T. zygis subsp. gracilis (Boiss.) Morales, T. x citriodorus (Pers.) Schreb. and T. fontqueri (Jalas) Molero e Rovira) using hydrodistillation and supercritical fluid CO2 extraction techniques, respectively. Furthermore, the aroma fingerprint of the plant materials was also characterized by collecting the volatiles through dynamic headspace-thermal desorption technique. In order to achieve that goal, the odor space was characterized by calculating odor values and by using an olfactory family model previously validated for both quantification and classification of volatile odorants. The obtained oils were characterized in terms of their organoleptic qualities as well as their chemical composition by gas chromatography coupled with mass spectrometry. A comparison amidst different species indicates that T. zygis and T. fontqueri show a phenolic type, mainly from high thymol and carvacrol content, respectively, while T. x citriodorus was richest in geraniol and citral. Furthermore, their organoleptic qualities also revealed odor similarities between T. zygis and T. fontqueri, both exhibiting a light herbaceous odor, in opposition to a strong lemon-herbaceous scent for T. x citriodorus. Hydrodistillation extraction yields ranged between 0.67% (w/w) for both T. zygis and T. fontqueri and 1.26% (w/w) for T. x citriodorus. In comparison, extraction yields for supercritical CO2 samples were lower for T. x citriodorus and T. fontqueri (<0.05%, w/w), while for T. zygis it was obtained as 0.78% (w/w). Finally, CO2 extracts were obtained for the first time for T. x citriodorus and T. fontqueri showing similar compositions to those obtained by hydrodistillation, although typically with lower phenolic and alcoholic content (especially for thymol, carvacrol, and geraniol). DHS analysis coupled with olfactory character models allowed us to classify both aroma and odor profiles of plants. In conclusion, coupling extraction techniques to obtain essential oils together with headspace volatile analysis appear to be a relevant approach for characterization of the fingerprint of plant materials, as well as establish a clear distinction amidst them.

Photodegradation of benzene, toluene and xylenes under visible light applying N-doped mixed TiO2 and ZnO catalysts

N-doped TiO2/ZnO catalysts were prepared by sol–gel technique and calcined at 380 and 500°C. Its photocatalytic activity was evaluated in the photodegradation of benzene, toluene and xylenes (BTX) under visible-LED light and compared with the undoped TiO2/ZnO activity. The amount of doped nitrogen was found to be 0.64at%. Concentrations of BTX were analysed by gas chromatography applying the headspace technique. The NTiO2/ZnO catalyst calcined at 500°C led to reductions of benzene, toluene and xylenes concentrations greater than 80wt% after 120min of irradiation. The photocatalytic reactions followed the first order kinetics.

Recovery of oxygenated ignitable liquids by zeolites, Part I: Novel extraction methodology in fire debris analysis

The recovery of low molecular weight oxygenates in fire debris samples is severely compromised by the use of heated passive headspace concentration with an activated charcoal strip, as outlined in ASTM E-1412. The term “oxygenate” is defined herein as a small, polar, organic molecule, such as acetone, methanol, ethanol, or isopropanol, which can be employed as an ignitable liquid and referred to in the ASTM classification scheme as the “oxygenated solvents” class. Although a well accepted technique, the higher affinity of activated carbon strips for heavy molecular weight products over low molecular weight products and hydrocarbons over oxygenated products, it does not allow for efficient recovery of oxygenates such as low molecular weight alcohols and acetone. The objective of this study was to develop and evaluate a novel method for the enhanced recovery of oxygenates from fire debris samples. By optimizing conditions of the heated passive headspace technique, the utilization of zeolites allowed for the successful collection and concentration of oxygenates. The results demonstrated that zeolites increased the recovery of oxygenates by at least 1.5-fold compared to the activated carbon strip and may complement the currently used extraction technique.

Chemometric analysis of volatiles of propolis from different regions using static headspace GC-MS

Abstract Six samples of propolis were analyzed in the paper: a sample from Brazil, Estonia, China and three samples from different locations of Uruguay. Static headspace technique coupled with gas chromatography-mass spectrometry analysis has been applied for the determination of the characteristic volatile profile with the aim to differentiate the propolis from different regions. Monoterpenes (α- and β-pinenes) were predominant in all samples, except the sample from China. This sample separated itself by the alcohols 3-methyl-3-buten-1-ol and 3-methyl-2-buten-1-ol, (40.33% and 11.57%, respectively) and ester 4-penten-1-yl acetate (9.04%). α-Pinene and β-pinene composed 64.59–77.56% of volatiles in Brazilian and Uruguayan propolis, and 29.43% in Estonian propolis. Brazilian propolis was distinguished by a high amount of β-methyl crotonaldehyde (10.11%), one of Uruguayan samples 3- by limonene (15.58%), and the Estonian sample — by eucalyptol (25.95%). Statistical investigation of the samples was made applying principal component, hierarchical cluster and K-Means cluster analyses. Various data pre-processing techniques were proposed and used to study and obtain the important volatile compounds contributed to the differentiation of the propolis samples from different regions to separate clusters.

Effect of extraction and concentration processes on properties of longan syrup.

Longan (Dimocarpus longan Lour.) syrup is a novel liquid sweetener produced from longan, one of the traditional and economic fruits in the Northern of Thailand. In this research, the effect of extraction and concentration processes on properties of longan syrup was investigated. There were two extraction methods (juice extractor and hydraulic press) and three concentration methods (direct heating, steam heating and vacuum evaporation). Results overall showed that the extraction method had no significant (p ≥ 0.05) effect on longan syrup properties, while concentration resulted in the quality changes of longan syrup. Concentration using direct heating of longan juice caused reduction of sucrose content, and longan syrup dark in color. The headspace volatile compounds of longan syrup were sampled using direct headspace technique and further characterized using gas chromatography-mass spectrometry. The identified volatile compounds could be divided into two groups of aroma characteristics which were (1) floral aroma: 3-methybutyl acetate, (β)-ocimene and 2-phenylethyl alcohol and (2) caramel aroma: butyraldehyde, furfural and benzaldehyde. 2-Phenylethyl alcohol, contributing to floral odor, was retained using vacuum evaporation as a concentration method. Result revealed that the optimal concentration process for longan syrup production was vacuum evaporation, providing the highest floral volatile and lowest caramel volatile. Sensory tests confirmed that longan flavor of the syrup produced from the vacuum evaporation process had significantly higher hedonic scores than other processes.

Extraction optimization using Box–Behnken design and method validation for ethanol in oral fluid

An optimization was proposed for the extraction of ethanol from oral fluid (OF) using the headspace (HS) technique, through experimental design and subsequent development and validation of an analytical method using HS-GC/FID and HS-GC/MS.

HS-SPME/GC-MS Analysis of VOC and Multivariate Techniques Applied to the Discrimination of Brazilian Varieties of Mango

The present study analyzed the volatile compounds of three mango varieties (Tommy Atkins, Rosa and Espada) using the static headspace technique with SPME coupled to CG-MS. Multivariate methodologies, such as factorial design and response surface methodology, were used to optimize the conditions of adsorption and desorption of these substances. The data were evaluated by using principal components analysis (PCA) and hierarchical grouping analysis, in order to visualize grouping tendencies of volatile compounds. Thirty-seven volatile compounds belonging to different chemical classes, such as esters, terpenes, alcohols and others, were tentatively identified in the three varieties of mango. Amongst them, twenty-three presented chromatographic peaks with relative areas larger than 2%. The multivariate analysis made it possible to visualize the grouping tendencies of the mango samples, according to the presence of their respective volatile substances, and enabled the identification of the groups of substances responsible for the discrimination among the three varieties.