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1.  Noninvasive detection of lung cancer by analysis of exhaled breath 
BMC Cancer  2009;9:348.
Background
Lung cancer is one of the leading causes of death in Europe and the western world. At present, diagnosis of lung cancer very often happens late in the course of the disease since inexpensive, non-invasive and sufficiently sensitive and specific screening methods are not available. Even though the CT diagnostic methods are good, it must be assured that "screening benefit outweighs risk, across all individuals screened, not only those with lung cancer". An early non-invasive diagnosis of lung cancer would improve prognosis and enlarge treatment options. Analysis of exhaled breath would be an ideal diagnostic method, since it is non-invasive and totally painless.
Methods
Exhaled breath and inhaled room air samples were analyzed using proton transfer reaction mass spectrometry (PTR-MS) and solid phase microextraction with subsequent gas chromatography mass spectrometry (SPME-GCMS). For the PTR-MS measurements, 220 lung cancer patients and 441 healthy volunteers were recruited. For the GCMS measurements, we collected samples from 65 lung cancer patients and 31 healthy volunteers. Lung cancer patients were in different disease stages and under treatment with different regimes. Mixed expiratory and indoor air samples were collected in Tedlar bags, and either analyzed directly by PTR-MS or transferred to glass vials and analyzed by gas chromatography mass spectrometry (GCMS). Only those measurements of compounds were considered, which showed at least a 15% higher concentration in exhaled breath than in indoor air. Compounds related to smoking behavior such as acetonitrile and benzene were not used to differentiate between lung cancer patients and healthy volunteers.
Results
Isoprene, acetone and methanol are compounds appearing in everybody's exhaled breath. These three main compounds of exhaled breath show slightly lower concentrations in lung cancer patients as compared to healthy volunteers (p < 0.01 for isoprene and acetone, p = 0.011 for methanol; PTR-MS measurements). A comparison of the GCMS-results of 65 lung cancer patients with those of 31 healthy volunteers revealed differences in concentration for more than 50 compounds. Sensitivity for detection of lung cancer patients based on presence of (one of) 4 different compounds not arising in exhaled breath of healthy volunteers was 52% with a specificity of 100%. Using 15 (or 21) different compounds for distinction, sensitivity was 71% (80%) with a specificity of 100%. Potential marker compounds are alcohols, aldehydes, ketones and hydrocarbons.
Conclusion
GCMS-SPME is a relatively insensitive method. Hence compounds not appearing in exhaled breath of healthy volunteers may be below the limit of detection (LOD). PTR-MS, on the other hand, does not need preconcentration and gives much more reliable quantitative results then GCMS-SPME. The shortcoming of PTR-MS is that it cannot identify compounds with certainty. Hence SPME-GCMS and PTR-MS complement each other, each method having its particular advantages and disadvantages. Exhaled breath analysis is promising to become a future non-invasive lung cancer screening method. In order to proceed towards this goal, precise identification of compounds observed in exhaled breath of lung cancer patients is necessary. Comparison with compounds released from lung cancer cell cultures, and additional information on exhaled breath composition in other cancer forms will be important.
doi:10.1186/1471-2407-9-348
PMCID: PMC2761408  PMID: 19788722
2.  Chilling-Induced Changes in Aroma Volatile Profiles in Tomato 
Food and Bioprocess Technology  2015;8(7):1442-1454.
Fruit and vegetables are regularly stored by consumers in the refrigerator at temperatures that may be well below the recommended storage temperatures. Apart from causing visible symptoms such as watery, sunken areas on the skin, chilling may also induce changes in fruit textural properties and flavour. The aim of this research was to investigate the effect of low temperature storage on tomato flavour and off-flavour production. To more closely mimic the real-consumer aroma perception while eating, in addition to the standard solid-phase microextraction gas chromatography–mass spectrometry (SPME/GC-MS) analysis, volatiles were also measured using a chewing device connected to a proton-transfer reaction–mass spectrometer (PTR-MS). Aroma volatiles were assessed in red ripe tomatoes of the cvs Cappricia RZ (round truss) and Amoroso RZ (cocktail truss) stored at refrigerator temperature (4 °C) and at higher temperatures (16 and 22 °C) for 20 days. The changes in aroma production were also monitored when the fruit was brought from room to refrigerator temperature and vice versa. After bringing the fruit from room to refrigerator temperature, the abundance of most volatiles was greatly reduced within 3 to 5 h, closely following the decrease in fruit temperature. When temperature was restored to room temperature following varying times of cold storage, the abundance of most volatiles increased again, but generally not to the original levels. Overall, the effects of low temperature storage on the decrease in volatile abundance were more pronounced in cv Cappricia RZ than in cv Amoroso RZ. On the contrary, the production of off flavours following prolonged cold storage was more pronounced in cv Amoroso RZ than in cv Cappricia RZ. Apart from changes in the overall abundance of the volatiles, marked changes in the volatile profile were observed in fruit stored for longer times in the cold and this may at least in part explain the negative effect of cold storage on overall tomato flavour.
doi:10.1007/s11947-015-1504-1
PMCID: PMC4579789  PMID: 26413182
Solanum lycopersicum L.; PTR-MS; GC-MS; Volatile compounds; Chilling injury
3.  A powerful approach to explore the potential of medicinal plants as a natural source of odor and antioxidant compounds 
In this study an efficient and reliable method based on dynamic headspace solid-phase microextraction (HS-SPME) followed by gas chromatography–mass spectrometry (GC–qMS), was developed to establish the volatile metabolomic pattern of Thymus vulgaris L., Rosmarinus officinalis L. and Ruta chalepensis L. medicinal plants. The HS-SPME influencing parameters were investigated and the results indicated that the best extraction capability, was obtained using DVB/CAR/PDMS coating fiber at 40 °C for 45 min. Under optimal conditions, a total of 99 volatile metabolites were identified, including 53 terpenoids, 19 carbonyl compounds, 7 esters, 6 alcohols, among others. The main volatile metabolites identified in T. vulgaris include thymol (67 %), 3-octanone (9 %) and 1-octen-3-ol (7 %), while in R. officinalis the most dominant volatiles were eucalyptol (40 %), 2-decanone (20 %) and bornyl acetate (10 %). 2-Undecanone (53 %), (E)-2-octenal (28 %) and 2-nonanone (10 %) were the most relevant volatile metabolites identified in R. chalepensis. The results suggested that the HS-SPME/GC-qMS methodology is a powerful approach to establish the volatile metabolomic fingerprint of medicinal plants and providing a reliable tool for the complete characterization of these biologically active medicinal plants.
doi:10.1007/s13197-015-2022-x
PMCID: PMC4711449  PMID: 26787937
Medicinal plants; Volatile metabolite; Solid-phase microextraction; GC-qMS; Antioxidant capacity
4.  Determination of Volatile Compounds in Four Commercial Samples of Japanese Green Algae Using Solid Phase Microextraction Gas Chromatography Mass Spectrometry 
The Scientific World Journal  2014;2014:289780.
Green algae are of great economic importance. Seaweed is consumed fresh or as seasoning in Japan. The commercial value is determined by quality, color, and flavor and is also strongly influenced by the production area. Our research, based on solid phase microextraction gas chromatography mass spectrometry (SPME-GC-MS), has revealed that volatile compounds differ intensely in the four varieties of commercial green algae. Accordingly, 41 major volatile compounds were identified. Heptadecene was the most abundant compound from Okayama (Ulva prolifera), Tokushima (Ulva prolifera), and Ehime prefecture (Ulva linza). Apocarotenoids, such as ionones, and their derivatives were prominent volatiles in algae from Okayama (Ulva prolifera) and Tokushima prefecture (Ulva prolifera). Volatile, short chained apocarotenoids are among the most potent flavor components and contribute to the flavor of fresh, processed algae, and algae-based products. Benzaldehyde was predominant in seaweed from Shizuoka prefecture (Monostroma nitidum). Multivariant statistical analysis (PCA) enabled simple discrimination of the samples based on their volatile profiles. This work shows the potential of SPME-GC-MS coupled with multivariant analysis to discriminate between samples of different geographical and botanical origins and form the basis for development of authentication methods of green algae products, including seasonings.
doi:10.1155/2014/289780
PMCID: PMC3921977  PMID: 24592162
5.  Production of isotopically-labeled standards from a uniformly labeled precursor for quantitative volatile metabolomic studies 
Analytical Chemistry  2012;84(12):5400-5406.
Optimal accuracy and precision in small molecule profiling by mass spectrometry generally requires isotopically labeled standards chemically representative of all compounds of interest. However, preparation of mixed standards from commercially available pure compounds is often prohibitively expensive and time consuming, and many labeled compounds are not available in pure form. We used a single prototype uniformly labeled [U-13C]-compound to generate [U-13C]-volatile standards for use in subsequent experimental profiling studies. [U-13C]-α-linolenic acid (C18:3n-3, ALA) was thermally oxidized to produce labeled lipid degradation volatiles which were subsequently characterized qualitatively and quantitatively. Twenty-five [U-13C]-labeled volatiles were identified by headspace solid-phase microextraction-gas chromatography-time of flight-mass spectrometry (HS-SPME-GC-TOF-MS) by comparison of spectra with unlabeled volatiles. Using 250 μL starting sample, labeled volatiles were quantified by a reverse isotope dilution procedure. Using the [U-13C]-labeled standards, limits of detection comparable to or better than previous HS-SPME reports were achieved, 0.010–1.04 ng/g. The performance of the [U-13C]-volatile standards was evaluated using a commodity soybean oil (CSO) oxidized at 60°C from 0 to 15 d. Relative responses of n-decane, an unlabeled internal standard otherwise absent from the mixture, and [U-13C]-oxidation products changed by up to 8-fold as the CSO matrix was oxidized, demonstrating that reliance on a single standard in volatile profiling studies yields inaccurate results due to changing matrix effects. The [U-13C]-standard mixture was used to quantify 25 volatiles in oxidized CSO and low-ALA soybean oil with an average relative standard deviation of 8.5%. Extension of this approach to other labeled substrates, e.g., [U-13C]-sugars and amino acids, for profiling studies should be feasible and can dramatically improve quantitative results compared to use of a single standard.
doi:10.1021/ac300933d
PMCID: PMC3381853  PMID: 22662968
Stable isotope metabolic labeling; lipids; uniformly labeled standard; soybean oil; metabolomics; lipidomics
6.  The GC/MS Analysis of Volatile Components Extracted by Different Methods from Exocarpium Citri Grandis 
Volatile components from Exocarpium Citri Grandis (ECG) were, respectively, extracted by three methods, that is, steam distillation (SD), headspace solid-phase microextraction (HS-SPME), and solvent extraction (SE). A total of 81 compounds were identified by gas chromatography-mass spectrometry including 77 (SD), 56 (HS-SPME), and 48 (SE) compounds, respectively. Despite of the extraction method, terpenes (39.98~57.81%) were the main volatile components of ECG, mainly germacrene-D, limonene, 2,6,8,10,14-hexadecapentaene, 2,6,11,15-tetramethyl-, (E,E,E)-, and trans-caryophyllene. Comparison was made among the three methods in terms of extraction profile and property. SD relatively gave an entire profile of volatile in ECG by long-time extraction; SE enabled the analysis of low volatility and high molecular weight compounds but lost some volatiles components; HS-SPME generated satisfactory extraction efficiency and gave similar results to those of SD at analytical level when consuming less sample amount, shorter extraction time, and simpler procedure. Although SD and SE were treated as traditionally preparative extractive techniques for volatiles in both small batches and large scale, HS-SPME coupled with GC/MS could be useful and appropriative for the rapid extraction and qualitative analysis of volatile components from medicinal plants at analytical level.
doi:10.1155/2013/918406
PMCID: PMC3855974  PMID: 24349825
7.  Can Volatile Organic Metabolites Be Used to Simultaneously Assess Microbial and Mite Contamination Level in Cereal Grains and Coffee Beans? 
PLoS ONE  2013;8(4):e59338.
A novel approach based on headspace solid-phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry (GC×GC–ToFMS) was developed for the simultaneous screening of microbial and mite contamination level in cereals and coffee beans. The proposed approach emerges as a powerful tool for the rapid assessment of the microbial contamination level (ca. 70 min versus ca. 72 to 120 h for bacteria and fungi, respectively, using conventional plate counts), and mite contamination (ca. 70 min versus ca. 24 h). A full-factorial design was performed for optimization of the SPME experimental parameters. The methodology was applied to three types of rice (rough, brown, and white rice), oat, wheat, and green and roasted coffee beans. Simultaneously, microbiological analysis of the samples (total aerobic microorganisms, moulds, and yeasts) was performed by conventional plate counts. A set of 54 volatile markers was selected among all the compounds detected by GC×GC–ToFMS. Principal Component Analysis (PCA) was applied in order to establish a relationship between potential volatile markers and the level of microbial contamination. Methylbenzene, 3-octanone, 2-nonanone, 2-methyl-3-pentanol, 1-octen-3-ol, and 2-hexanone were associated to samples with higher microbial contamination level, especially in rough rice. Moreover, oat exhibited a high GC peak area of 2-hydroxy-6-methylbenzaldehyde, a sexual and alarm pheromone for adult mites, which in the other matrices appeared as a trace component. The number of mites detected in oat grains was correlated to the GC peak area of the pheromone. The HS-SPME/GC×GC–ToFMS methodology can be regarded as the basis for the development of a rapid and versatile method that can be applied in industry to the simultaneous assessment the level of microbiological contamination and for detection of mites in cereals grains and coffee beans.
doi:10.1371/journal.pone.0059338
PMCID: PMC3628908  PMID: 23613710
8.  Volatile profile analysis and quality prediction of Longjing tea (Camellia sinensis) by HS-SPME/GC-MS 
This study aimed to analyze the volatile chemical profile of Longjing tea, and further develop a prediction model for aroma quality of Longjing tea based on potent odorants. A total of 21 Longjing samples were analyzed by headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Pearson’s linear correlation analysis and partial least square (PLS) regression were applied to investigate the relationship between sensory aroma scores and the volatile compounds. Results showed that 60 volatile compounds could be commonly detected in this famous green tea. Terpenes and esters were two major groups characterized, representing 33.89% and 15.53% of the total peak area respectively. Ten compounds were determined to contribute significantly to the perceived aroma quality of Longjing tea, especially linalool (0.701), nonanal (0.738), (Z)-3-hexenyl hexanoate (−0.785), and β-ionone (−0.763). On the basis of these 10 compounds, a model (correlation coefficient of 89.4% and cross-validated correlation coefficient of 80.4%) was constructed to predict the aroma quality of Longjing tea. Summarily, this study has provided a novel option for quality prediction of green tea based on HS-SPME/GC-MS technique.
doi:10.1631/jzus.B1200086
PMCID: PMC3520451  PMID: 23225852
Partial least square (PLS) regression; Green tea; Headspace solid phase microextraction (HS-SPME); Volatile profile; Quality prediction
9.  Solid-phase Microextraction (SPME) with Stable Isotope Calibration for Measuring Bioavailability of Hydrophobic Organic Contaminants 
Environmental science & technology  2013;47(17):9833-9840.
Solid-phase microextraction (SPME) is a biomimetic tool ideally suited for measuring bioavailability of hydrophobic organic compounds (HOCs) in sediment and soil matrices. However, conventional SPME sampling requires the attainment of equilibrium between the fiber and sample matrix, which may take weeks or months, greatly limiting its applicability. In this study, we explored the preloading of polydimethylsiloxane fiber with stable isotope labeled analogs (SI-SPME) to circumvent the need for long sampling time, and evaluated the performance of SI-SPME against the conventional equilibrium SPME (Eq-SPME) using a range of sediments and conditions. Desorption of stable isotope-labeled analogs and absorption of PCB-52, PCB-153, bifenthrin and cis-permethrin were isotropic, validating the assumption for SI-SPME. Highly reproducible preloading was achieved using acetone-water (1:4, v/v) as the carrier. Compared to Eq-SPME that required weeks or even months, the fiber concentrations (Cf) under equilibrium could be reliably estimated by SI-SPME in 1 d under agitated conditions or 20 d under static conditions in spiked sediments. The Cf values predicted by SI-SPME were statistically identical to those determined by Eq-SPME. The SI-SPME method was further applied successfully to field sediments contaminated with PCB 52, PCB 153, and bifenthrin. The increasing availability of stable isotope labeled standards and mass spectrometry nowadays makes SI-SPME highly feasible, allowing the use of SPME under non-equilibrium conditions with much shorter or flexible sampling time.
doi:10.1021/es4022987
PMCID: PMC3923886  PMID: 23930601
10.  Dependence of exhaled breath composition on exogenous factors, smoking habits and exposure to air pollutants* 
Journal of breath research  2012;6(3):10.1088/1752-7155/6/3/036008.
Non-invasive disease monitoring on the basis of volatile breath markers is a very attractive but challenging task. Several hundreds of compounds have been detected in exhaled air using modern analytical techniques (e.g. proton-transfer reaction mass spectrometry, gas chromatography-mass spectrometry) and have even been linked to various diseases. However, the biochemical background for most of compounds detected in breath samples has not been elucidated; therefore, the obtained results should be interpreted with care to avoid false correlations. The major aim of this study was to assess the effects of smoking on the composition of exhaled breath. Additionally, the potential origin of breath volatile organic compounds (VOCs) is discussed focusing on diet, environmental exposure and biological pathways based on other’s studies. Profiles of VOCs detected in exhaled breath and inspired air samples of 115 subjects with addition of urine headspace derived from 50 volunteers are presented. Samples were analyzed with GC-MS after preconcentration on multibed sorption tubes in case of breath samples and solid phase micro-extraction (SPME) in the case of urine samples. Altogether 266 compounds were found in exhaled breath of at least 10% of the volunteers. From these, 162 compounds were identified by spectral library match and retention time (based on reference standards). It is shown that the composition of exhaled breath is considerably influenced by exposure to pollution and indoor-air contaminants and particularly by smoking. More than 80 organic compounds were found to be significantly related to smoking, the largest group comprising unsaturated hydrocarbons (29 dienes, 27 alkenes and 3 alkynes). On the basis of the presented results, we suggest that for the future understanding of breath data it will be necessary to carefully investigate the potential biological origin of volatiles, e.g., by means of analysis of tissues, isolated cell lines or other body fluids. In particular, VOCs linked to smoking habit or being the results of human exposure should be considered with care for clinical diagnosis since small changes in their concentration profiles (typically in the pptv–ppbv range) revealing that the outbreak of certain disease might be hampered by already high background.
doi:10.1088/1752-7155/6/3/036008
PMCID: PMC3863686  PMID: 22932429
11.  Trapping the Pasture Odorscape Using Open-Air Solid-Phase Micro Extraction, a Tool to Assess Grassland Value 
PLoS ONE  2015;10(11):e0140600.
Besides supporting cattle feeding, grasslands are home to a diversity of plants and insects that interact with each other by emitting volatile compounds. The aim of this work was to develop a method to determine permanent grassland odorscape and relate it to flower-visiting insects. Two grasslands were chosen for their contrasting levels of botanical diversity, resulting from differing grazing managements. Measurements were made over two periods of three consecutive days at the beginning of grazing, and just after the cows had left the plots. Volatile compounds were trapped using solid-phase microextraction (SPME) fibers exposed eight hours a day in three exclosures per plot, and then analyzed by gas-chromatography-mass spectrometry (GC-MS). Insects were trapped using pan traps and a net, sorted and counted. The open air SPME method yielded volatile compound profiles that were richer than maize field profiles, comprising the common green leaf volatiles (GLV) and more specific ones. Differences between the odorscapes of the two grasslands were found, but they were not as marked as expected from their botanical composition. By contrast, there were sharp differences between the two periods, resulting from the combined effects of changes in weather conditions, plant phenological stage and grazing progress. Several correlations between insect counts and volatile compounds were found. Although their correlation coefficients were low, some of them were confirmed when tested by Spearman rank correlation, and could be logically explained. This method of grassland odorscape deserves to be developed because it can provide information on many aspects of grassland function and on the stresses that grassland plants undergo.
doi:10.1371/journal.pone.0140600
PMCID: PMC4633103  PMID: 26536369
12.  Simultaneous Analysis of 22 Volatile Organic Compounds in Cigarette Smoke Using Gas Sampling Bags for High-Throughput Solid-Phase Microextraction 
Analytical chemistry  2014;86(14):7088-7095.
Quantifying volatile organic compounds (VOCs) in cigarette smoke is necessary to establish smoke-related exposure estimates and evaluate emerging products and potential reduced-exposure products. In response to this need, we developed an automated, multi-VOC quantification method for machine-generated, mainstream cigarette smoke using solidphase microextraction gas chromatography–mass spectrometry (SPME-GC–MS). This method was developed to simultaneously quantify a broad range of smoke VOCs (i.e., carbonyls and volatiles, which historically have been measured by separate assays) for large exposure assessment studies. Our approach collects and maintains vapor-phase smoke in a gas sampling bag, where it is homogenized with isotopically labeled analogue internal standards and sampled using gas-phase SPME. High throughput is achieved by SPME automation using a CTC Analytics platform and custom bag tray. This method has successfully quantified 22 structurally diverse VOCs (e.g., benzene and associated monoaromatics, aldehydes and ketones, furans, acrylonitrile, 1,3-butadiene, vinyl chloride, and nitromethane) in the microgram range in mainstream smoke from 1R5F and 3R4F research cigarettes smoked under ISO (Cambridge Filter or FTC) and Intense (Health Canada or Canadian Intense) conditions. Our results are comparable to previous studies with few exceptions. Method accuracy was evaluated with third-party reference samples (≤15% error). Short-term diffusion losses from the gas sampling bag were minimal, with a 10% decrease in absolute response after 24 h. For most analytes, research cigarette inter- and intrarun precisions were ≤20% relative standard deviation (RSD). This method provides an accurate and robust means to quantify VOCs in cigarette smoke spanning a range of yields that is sufficient to characterize smoke exposure estimates.
doi:10.1021/ac5015518
PMCID: PMC4553414  PMID: 24933649
13.  Assessment of Volatile Chemical Composition of the Essential Oil of Jatropha ribifolia (Pohl) Baill by HS-SPME-GC-MS Using Different Fibers 
The chemical composition of essential oil and volatile obtained from the roots of Jatropha ribifolia (Pohl) Baill was performed in this work. The Clevenger extractor was utilized in hydrodistillation of oil and chemical composition determined by gas chromatography coupled with mass spectrometry detector (GC-MS). The identification of compounds was confirmed by retention index (Kovats index) obtained from a series of straight chain alkanes (C7–C30) and by comparison with NIST and ADAMS library. A total of 61 compounds were identified in essential oil by GC-MS. The extraction of volatile was performed also by the use of the solid phase microextraction (SPME) with four different fibers. The essential oil extraction was extremely rapid (15 s) to avoid saturation of the fiber and the MS detector. The majority of the composition of essential oil is the terpenes: β-pinene (major compound 9.16%), β-vatirene (8.34%), α-gurjunene (6.98%), α-pinene (6.35%), camphene (4.34%), tricyclene (3.79%) and dehydro aromadendrene (3.52%) it and aldehydes and alcohols. Through the SPME it was possible to determine the nine volatile compounds not identified in oil 2,3,4-trimethyl-2-cyclopenten-1-one, α-phellandrene, 3-carene, trans-p-mentha-2,8-dienol, pinocamphone, D-verbenon, 1,3,3-trimethyl-2-(2-methyl-cyclopropyl)-cyclohexene, 2,4-diisocyanato-1-methylbenzene, and (6-hydroxymethyl-2,3-dimethylehenyl) methanol.
doi:10.1155/2013/352606
PMCID: PMC3859261  PMID: 24371539
14.  Investigation on proteolysis and formation of volatile compounds of Lighvan cheese during ripening 
Journal of Food Science and Technology  2012;51(10):2454-2462.
The volatile compounds and protein profiles of Lighvan cheese, (raw traditional sheep cheese) were investigated over a 90-days ripening period. Solid-phase microextraction–gas chromatography–mass spectrometry [SPME–GC–MS] and sodium dodecyl sulfate polyacrylamide gel electrophoresis [SDS-PAGE] were used to identify volatile compounds and assess proteolysis assessment, respectively. Ripening breakdown products viz., acids (butanoic acid, 3 methyl butanoic acid, hexanoic acid, octanoic acid, decanoic acid,…) comprised of the highest number of detected individual compounds (10) followed by esters (9), alcohols (7), cyclic aromatic compounds (6), ketones (5) and aldehydes (4). Carboxylic acids were the dominant identified group; their levels increased during ripening and involved 48.22 % of the total volatile compounds at the end (90 days) of ripening. Esters, ketones, cyclic aromatic compounds and aldehydes also increased, whereas the alcohol content slightly decreased towards the end of the ripening. Degradation of β- and αS- casein was higher during the initial stage of ripening (1st month) of ripening than at later stages, which could be related to the inhibitory effect of salt on some bacteria and proteolytic enzymes.
doi:10.1007/s13197-012-0755-3
PMCID: PMC4190257  PMID: 25328184
Lighvan cheese; Proteolysis; Ripening; Volatile compounds
15.  Development of a Direct Headspace Collection Method from Arabidopsis Seedlings Using HS-SPME-GC-TOF-MS Analysis 
Metabolites  2013;3(2):223-242.
Plants produce various volatile organic compounds (VOCs), which are thought to be a crucial factor in their interactions with harmful insects, plants and animals. Composition of VOCs may differ when plants are grown under different nutrient conditions, i.e., macronutrient-deficient conditions. However, in plants, relationships between macronutrient assimilation and VOC composition remain unclear. In order to identify the kinds of VOCs that can be emitted when plants are grown under various environmental conditions, we established a conventional method for VOC profiling in Arabidopsis thaliana (Arabidopsis) involving headspace-solid-phase microextraction-gas chromatography-time-of-flight-mass spectrometry (HS-SPME-GC-TOF-MS). We grew Arabidopsis seedlings in an HS vial to directly perform HS analysis. To maximize the analytical performance of VOCs, we optimized the extraction method and the analytical conditions of HP-SPME-GC-TOF-MS. Using the optimized method, we conducted VOC profiling of Arabidopsis seedlings, which were grown under two different nutrition conditions, nutrition-rich and nutrition-deficient conditions. The VOC profiles clearly showed a distinct pattern with respect to each condition. This study suggests that HS-SPME-GC-TOF-MS analysis has immense potential to detect changes in the levels of VOCs in not only Arabidopsis, but other plants grown under various environmental conditions.
doi:10.3390/metabo3020223
PMCID: PMC3901263  PMID: 24957989
solid-phase microextraction; HS-SPME-GC-TOF-MS; volatile organic compounds; VOC profiling; Arabidopsis
16.  Anti-malarial activity and HS-SPME-GC-MS chemical profiling of Plinia cerrocampanensis leaf essential oil 
Malaria Journal  2014;13:18.
Background
Plinia cerrocampanensis is an endemic plant of Panama. The leaf essential oil of this plant has shown antibacterial activity. However, anti-malarial activity and chemical profiling by HS-SPME-GC-MS of this essential oil have not been reported before.
Methods
Anti-malarial activity of the essential oil (EO) was evaluated in vitro against chloroquine-sensitive HB3 and chloroquine-resistant W2 strains of Plasmodium falciparum. Synergistic effect of chloroquine and the EO on parasite growth was evaluated by calculating the combination index. A methodology involving headspace solid phase microextraction and gas chromatography-mass spectrometry (HS-SPME-GC-MS) was developed to investigate the composition of Plinia cerrocampanensis EO.
Results
Plinia cerrocampanensis EO showed a high anti-malarial activity and a synergistic interaction with chloroquine. The Plinia cerrocampanensis EO inhibited P. falciparum growth in vitro at an IC50 of 7.3 μg/mL. Chloroquine together with the EO decreased the IC50 of chloroquine from 0.1 μg/mL to 0.05 μg/mL, and of the EO from 7.3 μg/mL to 1.1 μg/mL. The measured combination index was 0.58, which clearly indicates that the EO acts synergistically with chloroquine. Since the EO maintained its inhibitory activity on the chloroquine-sensitive strain of the parasite, it could be acting by a different mechanism of action than chloroquine. The best HS-SPME-GC-MS analytical conditions were obtained when the temperature of extraction was 49°C, incubation time 14 min, and the time of extraction 10 min. This method allowed for the identification of 53 volatile constituents in the EO, including new compounds not reported earlier.
Conclusions
The anti-malarial activity exhibited by the Plinia cerrocampanensis EO may lend support for its possible use as an alternative for anti-malarial therapy.
doi:10.1186/1475-2875-13-18
PMCID: PMC3898253  PMID: 24410874
Malaria; Plinia cerrocampanensis; Plasmodium falciparum; Essential oil; Anti-malarial activity; Solid phase microextraction; Gas chromatography-mass spectrometry
17.  Rapid total volatile organic carbon quantification from microbial fermentation using a platinum catalyst and proton transfer reaction-mass spectrometry 
AMB Express  2016;6:90.
A novel analytical system was developed to rapidly and accurately quantify total volatile organic compound (VOC) production from microbial reactor systems using a platinum catalyst and a sensitive CO2 detector. This system allows nearly instantaneous determination of total VOC production by utilizing a platinum catalyst to completely and quantitatively oxidize headspace VOCs to CO2 in coordination with a CO2 detector. Measurement of respiratory CO2 by bypassing the catalyst allowed the total VOC content to be determined from the difference in the two signals. To the best of our knowledge, this is the first instance of a platinum catalyst and CO2 detector being used to quantify the total VOCs produced by a complex bioreactor system. Continuous recording of these CO2 data provided a record of respiration and total VOC production throughout the experiments. Proton transfer reaction-mass spectrometry (PTR-MS) was used to identify and quantify major VOCs. The sum of the individual compounds measured by PTR-MS can be compared to the total VOCs quantified by the platinum catalyst to identify potential differences in detection, identification and calibration. PTR-MS measurements accounted on average for 94 % of the total VOC carbon detected by the platinum catalyst and CO2 detector. In a model system, a VOC producing endophytic fungus Nodulisporium isolate TI-13 was grown in a solid state reactor utilizing the agricultural byproduct beet pulp as a substrate. Temporal changes in production of major volatile compounds (ethanol, methanol, acetaldehyde, terpenes, and terpenoids) were quantified by PTR-MS and compared to the total VOC measurements taken with the platinum catalyst and CO2 detector. This analytical system provided fast, consistent data for evaluating VOC production in the nonhomogeneous solid state reactor system.
Electronic supplementary material
The online version of this article (doi:10.1186/s13568-016-0264-2) contains supplementary material, which is available to authorized users.
doi:10.1186/s13568-016-0264-2
PMCID: PMC5052237  PMID: 27709547
Fungal endophyte; Proton transfer reaction-mass spectrometry; Solid state fermentation; Total volatile organic carbon
18.  Spoilage-Related Activity of Carnobacterium maltaromaticum Strains in Air-Stored and Vacuum-Packed Meat ▿ †  
Applied and Environmental Microbiology  2011;77(20):7382-7393.
One hundred three isolates of Carnobacterium spp. from raw meat were analyzed by random amplification of polymorphic DNA (RAPD) and PCR and were identified by 16S rRNA gene sequencing. Forty-five strains of Carnobacterium maltaromaticum were characterized for their growth capabilities at different temperatures, NaCl concentrations, and pH values and for in vitro lipolytic and proteolytic activities. Moreover, their spoilage potential in meat was investigated by analyzing the release of volatile organic compounds (VOCs) in meat stored in air or vacuum packs. Almost all the strains were able to grow at 4, 10, and 20°C, at pH values of 6 to 9, and in the presence of 2.5% NaCl. The release of VOCs by each strain in beef stored at 4°C in air and vacuum packs was evaluated by headspace solid-phase microextraction (HS-SPME)-gas chromatography-mass spectrometry (GC-MS) analysis. All the meat samples inoculated and stored in air showed higher numbers of VOCs than the vacuum-packed meat samples. Acetoin, 1-octen-3-ol, and butanoic acid were the compounds most frequently found under both storage conditions. The contaminated meat samples were evaluated by a sensory panel; the results indicated that for all sensory odors, no effect of strain was significant (P > 0.05). The storage conditions significantly affected (P < 0.05) the perception of dairy, spoiled-meat, and mozzarella cheese odors, which were more intense in meat stored in air than in vacuum packs but were never very intense. In conclusion, different strains of C. maltaromaticum can grow efficiently in meat stored at low temperatures both in air and in vacuum packs, producing volatile molecules with low sensory impacts, with a negligible contribution to meat spoilage overall.
doi:10.1128/AEM.05304-11
PMCID: PMC3194841  PMID: 21784913
19.  Biological activities and volatile constituents of Daucus muricatus L. from Algeria 
Background
In order to find new bioactive natural products, the antimicrobial and antioxidant activities of essential oil components extracted from the separated organs of the Algerian medicinal and aromatic plant Daucus muricatus L. were studied.
Results
The chemical composition of essential oils obtained by hydrodistillation (HD) was investigated using Gas Chromatography–Retention Indices (GC-RI) and GC–Mass Spectrometry (GC-MS). Two types of essential oils were produced by D. muricatus: (i) The oil from roots is mainly composed by nonterpenic oxygenated compounds (59.8 g/100 g), and (ii) the aerial part oils (i.e., the leaves, stems, flowers, and umbels) was mainly composed by terpenic hydrocarbon compounds (62.3–72.2 g/100 g). The chemical composition of the volatile fraction isolated from different organs of Daucus muricatus were studied by HS–SPME/GC–RI and GC–MS after optimization of Solid Phase MicroExtraction parameters. For all organs studied, the main volatiles emitted by the plant were hydrocarbon compounds (60.7–82.2 g/100 g). Only quantitative differences between the volatiles of the separated organs studied were observed. In addition, the activity of the oil of D. muricatus against eight bacterial strains and one yeast was investigated. The oil from roots revealed active against S. aureus, while the essential oil obtained from the aerial parts was active against the yeast C. albicans.
Conclusions
Daucus muricatus essential oil seems be a promising source of natural products with potential antimicrobial activity.
doi:10.1186/1752-153X-6-48
PMCID: PMC3444933  PMID: 22647252
Daucus muricatus. L; Essential oils; HS-SPME; GC/MS; Antimicrobial and antioxidant activities
20.  The volatile metabolome of grapevine roots: First insights into the metabolic response upon phylloxera attack 
Plant Physiology and Biochemistry  2011;49(9):1059-1063.
Many plant species respond to herbivore attack by an increased formation of volatile organic compounds. In this preliminary study we analysed the volatile metabolome of grapevine roots [Teleki 5C (Vitis berlandieri Planch. × Vitis riparia Michx.)] with the aim to gain insight into the interaction between phylloxera (Daktulosphaira vitifoliae Fitch; Hemiptera: Phylloxeridae) and grapevine roots. In the first part of the study, headspace solid phase microextraction (HS-SPME) coupled to gas chromatography – mass spectrometry (GC–MS) was used to detect and identify volatile metabolites in uninfested and phylloxera-infested root tips of the grapevine rootstock Teleki 5C. Based on the comparison of deconvoluted mass spectra with spectra databases as well as experimentally derived retention indices with literature values, 38 metabolites were identified, which belong to the major classes of plant volatiles including C6-compounds, terpenes (including modified terpenes), aromatic compounds, alcohols and n-alkanes. Based on these identified metabolites, changes in root volatiles were investigated and resulted in metabolite profiles caused by phylloxera infestation. Our preliminary data indicate that defence related pathways such as the mevalonate and/or alternative isopentenyl pyrophosphate-, the lipoxygenase- (LOX) as well as the phenylpropanoid pathway are affected in root galls as a response to phylloxera attack.
Highlights
► 38 volatiles identified in healthy and phylloxera-infested grapevine root samples by GC–MS. ► Fourteen differentially expressed metabolites in phylloxera-infested grapevine root tips. ► Root infestation by phylloxera is associated with defence response in grapevine. ► MEV/alt. IPP-, phenylpropanoid- and LOX pathways are affected upon phylloxera attack.
doi:10.1016/j.plaphy.2011.06.008
PMCID: PMC3268251  PMID: 21764593
Phylloxera; Nodosity; Volatile secondary metabolites; Metabolite profiling; HS-SPME–GC–MS; Vitis berlandieri × Vitis riparia; Rootstock
21.  Solid-phase microextraction/gas chromatography–mass spectrometry method optimization for characterization of surface adsorption forces of nanoparticles 
Analytical and Bioanalytical Chemistry  2014;406(26):6629-6636.
A complete characterization of the different physico-chemical properties of nanoparticles (NPs) is necessary for the evaluation of their impact on health and environment. Among these properties, the surface characterization of the nanomaterial is the least developed and in many cases limited to the measurement of surface composition and zetapotential. The biological surface adsorption index approach (BSAI) for characterization of surface adsorption properties of NPs has recently been introduced (Xia et al. Nat Nanotechnol 5:671–675, 2010; Xia et al. ACS Nano 5(11):9074–9081, 2011). The BSAI approach offers in principle the possibility to characterize the different interaction forces exerted between a NP's surface and an organic—and by extension biological—entity. The present work further develops the BSAI approach and optimizes a solid-phase microextraction gas chromatography–mass spectrometry (SPME/GC-MS) method which, as an outcome, gives a better-defined quantification of the adsorption properties on NPs. We investigated the various aspects of the SPME/GC-MS method, including kinetics of adsorption of probe compounds on SPME fiber, kinetic of adsorption of probe compounds on NP's surface, and optimization of NP's concentration. The optimized conditions were then tested on 33 probe compounds and on Au NPs (15 nm) and SiO2 NPs (50 nm). The procedure allowed the identification of three compounds adsorbed by silica NPs and nine compounds by Au NPs, with equilibrium times which varied between 30 min and 12 h. Adsorption coefficients of 4.66 ± 0.23 and 4.44 ± 0.26 were calculated for 1-methylnaphtalene and biphenyl, compared to literature values of 4.89 and 5.18, respectively. The results demonstrated that the detailed optimization of the SPME/GC-MS method under various conditions is a critical factor and a prerequisite to the application of the BSAI approach as a tool to characterize surface adsorption properties of NPs and therefore to draw any further conclusions on their potential impact on health.
Graphical AbstractThe basic principle of SPME/GC-MS method for characterization of nanoparticles surface adsorption forces
doi:10.1007/s00216-014-8078-z
PMCID: PMC4182651  PMID: 25168112
Nanoparticles; Characterization; Interactions; Biomolecules
22.  Unbiased profiling of volatile organic compounds in the headspace of Allium plants using an in-tube extraction device 
BMC Research Notes  2016;9:133.
Background
Plants produce and emit important volatile organic compounds (VOCs), which have an essential role in biotic and abiotic stress responses and in plant–plant and plant–insect interactions. In order to study the bouquets from plants qualitatively and quantitatively, a comprehensive, analytical method yielding reproducible results is required.
Results
We applied in-tube extraction (ITEX) and solid-phase microextraction (SPME) for studying the emissions of Allium plants. The collected HS samples were analyzed by gas chromatography–time-of-flight–mass spectrometry (GC-TOF–MS), and the results were subjected to multivariate analysis. In case of ITEX-method Allium cultivars released more than 300 VOCs, out of which we provisionally identified 50 volatiles. We also used the VOC profiles of Allium samples to discriminate among groups of A. fistulosum, A. chinense (rakkyo), and A. tuberosum (Oriental garlic). As we found 12 metabolite peaks including dipropyl disulphide with significant changes in A. chinense and A. tuberosum when compared to the control cultivar, these metabolite peaks can be used for chemotaxonomic classification of A. chinense, tuberosum, and A. fistulosum.
Conclusions
Compared to SPME-method our ITEX-based VOC profiling technique contributes to automatic and reproducible analyses. Hence, it can be applied to high-throughput analyses such as metabolite profiling.
Electronic supplementary material
The online version of this article (doi:10.1186/s13104-016-1942-5) contains supplementary material, which is available to authorized users.
doi:10.1186/s13104-016-1942-5
PMCID: PMC4772445  PMID: 26928722
Volatile organic compounds; GC-TOF–MS; Metabolomics; Headspace; ITEX; Allium
23.  The Global Volatile Signature of Veal via Solid-phase Microextraction and Gas Chromatography-mass Spectrometry 
The volatile composition of veal has yet to be reported and is one of the important factors determining meat character and quality. To identify the most important aroma compounds in veal from Holstein bull calves fed one of three diets, samples were subjected to solid-phase microextraction (SPME) combined with gas chromatography-quadrupole mass spectrometry (GC-MS). Most of the important odorants were aldehydes and alcohols. For group A (veal calves fed entirely on milk for 90 d before slaughter), the most abundant compound class was the aldehydes (52.231%), while that was alcohols (26.260%) in group C (veal calves fed starter diet for at least 60 d before slaughter). In both classes the absolute percentages of the volatile compounds in veal were different indicating that the veal diet significantly (p<0.05) affected headspace volatile composition in veal as determined by principal component analysis (PCA). Twenty three volatile compounds showed significance by using a partial least-squared discriminate analysis (PLS-DA) (VIP>1). The establishment of the global volatile signature of veal may be a useful tool to define the beef diet that improves the organoleptic characteristics of the meat and consequently impacts both its taste and economic value.
doi:10.5851/kosfa.2014.34.5.700
PMCID: PMC4662233  PMID: 26761505
veal; volatile; SPME-GC-MS; PCA; PLS-DA
24.  Measurement of volatile organic compounds emitted in libraries and archives: an inferential indicator of paper decay? 
Background
A sampling campaign of indoor air was conducted to assess the typical concentration of indoor air pollutants in 8 National Libraries and Archives across the U.K. and Ireland. At each site, two locations were chosen that contained various objects in the collection (paper, parchment, microfilm, photographic material etc.) and one location was chosen to act as a sampling reference location (placed in a corridor or entrance hallway).
Results
Of the locations surveyed, no measurable levels of sulfur dioxide were detected and low formaldehyde vapour (< 18 μg m-3) was measured throughout. Acetic and formic acids were measured in all locations with, for the most part, higher acetic acid levels in areas with objects compared to reference locations. A large variety of volatile organic compounds (VOCs) was measured in all locations, in variable concentrations, however furfural was the only VOC to be identified consistently at higher concentration in locations with paper-based collections, compared to those locations without objects. To cross-reference the sampling data with VOCs emitted directly from books, further studies were conducted to assess emissions from paper using solid phase microextraction (SPME) fibres and a newly developed method of analysis; collection of VOCs onto a polydimethylsiloxane (PDMS) elastomer strip.
Conclusions
In this study acetic acid and furfural levels were consistently higher in concentration when measured in locations which contained paper-based items. It is therefore suggested that both acetic acid and furfural (possibly also trimethylbenzenes, ethyltoluene, decane and camphor) may be present in the indoor atmosphere as a result of cellulose degradation and together may act as an inferential non-invasive marker for the deterioration of paper. Direct VOC sampling was successfully achieved using SPME fibres and analytes found in the indoor air were also identified as emissive by-products from paper. Finally a new non-invasive, method of VOC collection using PDMS strips was shown to be an effective, economical and efficient way of examining VOC emissions directly from the pages of a book and confirmed that toluene, furfural, benzaldehyde, ethylhexanol, nonanal and decanal were the most concentrated VOCs emitted directly from paper measured in this study.
doi:10.1186/1752-153X-6-42
PMCID: PMC3439258  PMID: 22587759
Indoor air monitoring; Passive sampling; Active sampling; Tenax TA; Paper degradation; Library conservation
25.  Thermal treatment and leaching of biochar alleviates plant growth inhibition from mobile organic compounds 
PeerJ  2016;4:e2385.
Recent meta-analyses of plant responses to biochar boast positive average effects of between 10 and 40%. Plant responses, however, vary greatly across systems, and null or negative biochar effects are increasingly reported. The mechanisms responsible for such responses remain unclear. In a glasshouse experiment we tested the effects of three forestry residue wood biochars, applied at five dosages (0, 5, 10, 20, and 50 t/ha) to a temperate forest drystic cambisol as direct surface applications and as complete soil mixes on the herbaceous pioneers Lolium multiflorum and Trifolium repens. Null and negative effects of biochar on growth were found in most cases. One potential cause for null and negative plant responses to biochar is plant exposure to mobile compounds produced during pyrolysis that leach or evolve following additions of biochars to soil. In a second glasshouse experiment we examined the effects of simple leaching and heating techniques to ameliorate potentially phytotoxic effects of volatile and leachable compounds released from biochar. We used Solid Phase Microextraction (SPME)–gas chromatography–mass spectrometry (GC-MS) to qualitatively describe organic compounds in both biochar (through headspace extraction), and in the water leachates (through direct injection). Convection heating and water leaching of biochar prior to application alleviated growth inhibition. Additionally, growth was inhibited when filtrate from water-leached biochar was applied following germination. SPME-GC-MS detected primarily short-chained carboxylic acids and phenolics in both the leachates and solid chars, with relatively high concentrations of several known phytotoxic compounds including acetic acid, butyric acid, 2,4-di-tert-butylphenol and benzoic acid. We speculate that variable plant responses to phytotoxic organic compounds leached from biochars may largely explain negative plant growth responses and also account for strongly species-specific patterns of plant responses to biochar amendments in short-term experiments.
doi:10.7717/peerj.2385
PMCID: PMC5012324  PMID: 27635349
Biochar; Mobile organic compounds; Phytotoxicity; Leaching; Thermal treatment; Volatile organic compounds

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