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We present a generalised framework for resolving the electrochemistry-diffusion interface and modelling hydrogen transport near a crack tip. The adsorption and absorption kinetics are captured by means of Neumann-type generalised boundary conditions. The diffusion model includes the role of trapping, with a constant or evolving trap density, and the influence of the hydrostatic stress. Both conventional plasticity and strain gradient plasticity are used to model the mechanical behaviour of the solid. Notable differences are found in the estimated crack tip hydrogen concentrations when comparing with the common procedure of prescribing a constant hydrogen concentration at the crack surfaces., E. Martínez-Pañeda acknowledges financial support from EPSRC funding under grant no.EP/R010161/1, from the UKCRIC Coordination Node EPSRC grant number EP/R017727/1, which funds UKCRIC's ongoing coordination, and from Wolfson College Cambridge (Junior Research Fellowship). A. Díaz gratefully acknowledges financial support from the Ministry of Science, Innovation and Universities of Spain through grant RTI2018-096070-B-C33.

Several calibration approaches were evaluated for the quantitation of volatile organic compounds in air using miniaturized exhaustive and non-exhaustive sampling techniques, such as in-tube extraction (ITEX) and solid phase microextraction (SPME) Arrow. Eleven compounds, 2-ethyl-hexanol, hexanal, nonanal, toluene, ethyl-benzene, methyl isobutyl ketone, acetophenone, p-cymene, alpha-pinene, trimethylamine and triethylamine, all them found in the natural air samples, were selected as model analytes. Liquid injection, liquid standard addition to the sorbent bed and gas phase standards provided by an automatic permeation system, were evaluated in the case of ITEX packed with laboratory-made 10% polyacrylonitrile (PAN) material. Two different approaches, based on sampling of gas phase compounds from the permeation system and from sample vial containing gas phase standards, were evaluated for SPME Arrow with two different coatings, commercial divinylbenzene-poly(dimethylsiloxane) (DVB-PDMS) and laboratory-made mesoporous Mobil Composition of Matter No. 41 (MCM-41). In addition, interface model approach was used for the calculation of the real concentration of the target analytes in the sample from the total amount of analytes injected into the GC-MS in the case of SPME Arrow. Similar results were obtained with the different approaches used for the quantitation by ITEX and SPME Arrow. However, the use of gas phase standards with sample matrix similar to the natural samples, allowed the permeation system to provide the most reliable results for the quantitation of the target analytes. For this approach, linearity (expressed as r(2) values) ranged between 0.991 and 0.999. The limit of detection ranged from 0.5 mu g/m(3) (trimethylamine, MCM-41) to 2.2 x 10(-4) mu g/m(3) (methyl isobutyl ketone, MCM-41). In addition, the use of the fully automated permeation system provided good reproducibility values that were between 1.4% (acetophenone, MCM-41) and 7.8% (methyl isobutyl ketone, 10% PAN). The linear ranges were at least 3 order of magnitude for all the studied analytes with the exception of the calibration curve developed for trimethylamine with SPME Arrow (linear ranges between LOQ and 4.9 mu g/m(3) (DVB-PDMS) and LOQ and 9.8 mu g/m(3) (MCM-41)). (C) 2019 Elsevier B.V. All rights reserved.

Disease breathomics is gaining importance nowadays due to its usefulness as non-invasive early cancer detection. Mass spectrometry (MS) technique is often used for analysis of volatile organic compounds (VOCs) associated with cancer in the exhaled breath but a long-standing challenge is the uncertainty in mass peak annotation for potential volatile biomarkers. This work describes a cross-platform MS strategy employing selected-ion flow tube mass spectrometry (SIFT-MS), high resolution gas chromatography-mass spectrometry (GC-MS) retrofitted with electron ionisation (EI) and GC-MS retrofitted with positive chemical ionisation (PCI) as orthogonal analytical approaches in order to provide facile identification of the oxygenated VOCs from breath of cancer patients. In addition, water infusion was applied as novel efficient PCI reagent in breathomics analysis, depicting unique diagnostic ions M+ or [M-17]+ for VOC identification. Identity confirmation of breath VOCs was deduced using the proposed multi-platform workflow, which reveals variation in breath oxygenated VOC composition of oesophageal-gastric (OG) cancer patients with dominantly ketones, followed by aldehydes, alcohols, acids and phenols in decreasing order of relative abundance. Accurate VOC identification provided by cross-platform approach would be valuable for the refinement of diagnostic VOC models and the understanding of molecular drivers of VOC production.

Episodic accretion is an important process in the evolution of young stars and their environment. The observed strong luminosity bursts of young stellar objects likely have a long lasting impact on the chemical evolution of the disk and envelope structure. We want to investigate observational signatures of the chemical evolution in the post-burst phase for embedded sources. With such signatures it is possible to identify targets that experienced a recent luminosity burst. We present a new model for episodic accretion chemistry based on the 2D, radiation thermo-chemical disk code ProDiMo. We have extended ProDiMo with a proper treatment for envelope structures. For a representative Class I model, we calculated the chemical abundances in the post-burst phase and produced synthetic observables like intensity maps and radial profiles. During a burst many chemical species, like CO, sublimate from the dust surfaces. As the burst ends they freeze out again (post-burst phase). This freeze-out happens from inside-out due to the radial density gradient in the disk and envelope structure. This inside-out freeze-out produces clear observational signatures in spectral line emission, like rings and distinct features in the slope of radial intensity profiles. We fitted synthetic C18O J=2-1 observations with single and two component fits and find that post-burst images are much better matched by the latter. Comparing the quality of such fits allows identification of post-burst targets in a model-independent way. Our models confirm that it is possible to identify post-burst objects from spatially resolved CO observations. However, to derive proper statistics, like frequencies of bursts, from observations it is important to consider aspects like the inclination and structure of the target and also dust properties as those have a significant impact on the freeze-out timescale., Comment: 17 pages, 6 figures, 2 tables. Accepted for publication in A&A

The chemical and isotopic composition of organic aerosol (OA) samples collected on PM1 filters was determined as a function of desorption temperature to investigate the main sources of organic carbon and the effects of photochemical processing on atmospheric aerosol. The filter samples were collected at an urban (54 degrees 38' N, 25 degrees 18' E), coastal (55 degrees 55' N, 21 degrees 00' E) and forest (55 degrees 27' N, 26 degrees 00' E) site in Lithuania in March 2013. They can be interpreted as winter-time samples because the monthly averaged temperature was -4 degrees C.The detailed chemical composition of organic compounds was analysed with a thermal desorption PTR-MS. The mass concentration of organic aerosol at the forest site was roughly by a factor of 30 lower than at the urban and coastal site. This fact could be an indication that in this cold month the biogenic secondary organic aerosol (SOA) formation was very low. Moreover, the organic aerosol collected at the forest site was more refractory and contained a larger fraction of heavy molecules with m/z > 200.The isotopic composition of the aerosol was used to differentiate the two main sources of organic aerosol in winter, i.e. biomass burning (BB) and fossil fuel (FF) combustion. Organic aerosol from biomass burning is enriched in C-13 compared to OA from fossil fuel emissions. delta(13)Coc values of the OA samples showed a positive correlation with the mass fraction of several individual organic compounds. Most of these organic compounds contained nitrogen indicating that organic nitrogen compounds formed during the combustion of biomass may be indicative of BB. Other compounds that showed negative correlations with delta(13)Coc were possibly indicative of FF. These compounds included heavy hydrocarbons and were on the average less oxidized than the bulk organic carbon.The correlation of delta(13)Coc and the O/C ratio was positive at low but negative at high desorption temperatures at the forest site. We propose that this might be due to photochemical processing of OA. This processing can lead to accumulation of carbon in the more refractory organic fraction that is depleted C-13 compared with the less refractory organic fraction. Detailed laboratory experiments are necessary to further investigate the aging of aerosol particles before firm conclusions can be drawn. (C) 2016 Elsevier Ltd. All rights reserved.

Silicon dioxide films have been deposited at temperatures below 270 degrees C in an electron cyclotron resonance (ECR) plasma reactor from O-2, SiH4, and He gas mixture. Pinhole density analysis as a function of substrate temperature for different microwave powers was carried out. Films deposited at higher microwave power and at room temperature show defect densities (< 7 pinhole/mm(2)), ensuring low-temperature process integration on large area. From Fourier transform infrared analysis and thermal desorption spectrometry we also evaluated very low hydrogen content if compared to conventional rf-plasma-enhanced chemical-vapor-deposited (PECVD) SiO2 deposited at 350 degrees C. Electrical properties have been measured in metal-oxide-semiconductor (MOS) capacitors, depositing SiO2 at RT as gate dielectric; breakdown electric fields > 10 MV/cm and charge trapping at fields > 6 MV/cm have been evaluated. From the study of interface quality in MOS capacitors, we found that even for low annealing temperature (200 degrees C), it is possible to considerably reduce the interface state density down to 5 x 10(11) cm(-2) eV(-1). To fully validate the ECR-PECVD silicon dioxide we fabricated polycrystalline silicon thin-film transistors using RT-deposited SiO2 as gate insulator. Different postdeposition thermal treatments have been studied and good device characteristics were obtained even for annealing temperature as low as 200 degrees C.

Solid-phase extraction-pipette tips (SPE-PTs) were used for micro solid-phase extraction of lidocaine and diazepam from plasma. Off-line extraction was followed by on-line desorption. On-line desorption was carried out by direct coupling of the SPE-PTs with the liner of the programmed-temperature vaporiser. This coupling only required shortening of the liner by maximally 16 mm, cutting the SPE-PT, and equipping the remaining part with two O-rings. Due to the heating of the injector the SPE-PTs were heated as well, which resulted in a significant amount of impurities. Pre-heating and pre-washing was performed prior to the extraction to reduce the impurity level. The internal coupling device was applied successfully for the analysis of plasma samples with gas chromatography (GC) and mass-selective detection. Detection limits of 0.75 ng/ml and 2.5 ng/ml were obtained for lidocaine and diazepam, respectively, using 200 mul plasma. Recoveries for both compounds were about 80%. Although it is possible, the internal coupling device was not developed to be used as such. The main goal of this coupling was to show the feasibility of the integration of SPE-PTs with GC and to realize an important step to new automated SPE-GC systems. (C) 2002 Elsevier Science B.V. All rights reserved.

The use of a programmed temperature vaporiser (PTV) with a packed liner was evaluated for the injection of large volumes (up to 100 mu l) of plasma extracts in a gas chromatograph. Solvent purity, which is essential when large volumes are injected into the GC system, was determined. Special attention was paid to the purity of the solvents used for the solid-phase extraction (SPE) procedure. For this SPE method, ethyl acetate was used as the extraction and reconstitution solvent, and thus the purity of the ethyl acetate was critical, especially when a non-selective GC detector was applied. The liquid capacity and inertness of different packed liners were investigated. The liner packed with ATAS "A" (modified Chromosorb-based material with special treatment) was found to be the most suitable for the analysis of the tested drugs. Good linearity in response for variations in volume and concentration was observed. A comparison was made between the applicability of flame ionisation detection (FID) and mass-selective detection (MSD). When 50-mu l volumes of plasma extracts were injected with the PTV, the detection limits for secobarbital, lidocaine, phenobarbital and diazepam were about 50-times lower than when 1-mu l volumes were injected. The detection limits of the tested compounds in plasma for injection of 50-100 mu l plasma extract are 5-10 ng/ml for GC-FID whereas plasma concentrations of 250 pg/ml can be detected using the selected ion monitoring (SUI) mode of a MSD. For non-selective GC-FID, the background from a 50-mu l injection was substantially larger than with 1-mu l injection as a result of co-injected plasma matrix components and solvent impurities. These background effects were less with GC-MSD in the total ion current mode and virtually absent with GC-MSD in the SIM mode. (C) 1999 Elsevier Science B.V. All rights reserved.

Methods and models describing oxygen diffusion and desorption in oxides have been developed for slightly defective and well crystallised bulky materials. Does nanostructuring change the mechanism of oxygen mobility? In such a case, models should be properly checked and adapted to take into account new material properties. In order to do so, temperature programmed oxygen desorption and thermogravimetric analysis, either in isothermal or ramp mode, have been used to investigate some nanostructured La(1-x)A(x)MnO(3-delta) samples (A = Sr and Ce, 20-60 nm particle size) with perovskite-like structure. The experimental data have been elaborated by means of different models to define a set of kinetic parameters able to describe oxygen release properties and oxygen diffusion through the bulk. Different rate-determining steps have been identified, depending on the temperature range and oxygen depletion of the material. In particular, oxygen diffusion was shown to be rate-limiting at low temperature and at low defect concentration, whereas oxygen recombination at the surface seems to be the rate-controlling step at high temperature. However, the oxygen recombination step is characterised by an activation energy much lower than that for diffusion. In the present paper oxygen transport in nanosized materials is quantified by making use of widely diffused experimental techniques and by critically adapting to nanoparticles suitably chosen models developed for bulk materials

Rubidium adsorption on the surface of the topological insulator Bi 2Se 3 is found to induce a strong downward band bending, leading to the appearance of a quantum-confined two-dimensional electron gas state (2DEG) in the conduction band. The 2DEG shows a strong Rashba-type spin-orbit splitting, and it has previously been pointed out that this has relevance to nanoscale spintronics devices. The adsorption of Rb atoms, on the other hand, renders the surface very reactive, and exposure to oxygen leads to a rapid degrading of the 2DEG. We show that intercalating the Rb atoms, presumably into the van der Waals gaps in the quintuple layer structure of Bi 2Se 3, drastically reduces the surface reactivity while not affecting the promising electronic structure. The intercalation process is observed above room temperature and accelerated with increasing initial Rb coverage, an effect that is ascribed to the Coulomb interaction between the charged Rb ions. Coulomb repulsion is also thought to be responsible for a uniform distribution of Rb on the surface. © 2012 American Chemical Society., This work was supported by a grant from the Lundbeck Foundation. J.W.W. acknowledges financial support from the Institute for Storage Ring Facilities, Aarhus University. Z.M.A. acknowledges both the Spanish (MAT2010-21156-C03-01) and Basque Government (IT-257-07) for funding. P.L., L.Z., A.A.K., J.W., and R.W. acknowledge financial support from the Free and Hanseatic City of Hamburg via the Cluster of Excellence NANO-SPINTRONICS, from the Deutsche Forschungsgemeinschaft via the Graduiertenkolleg “Functional Metal-Semiconductor Hybrid Systems”, and from the European Research Council (ERC) Advanced Grant “FURORE”.

The gas/particle partitioning behaviour of the semi-volatile fraction of secondary organic matter and the associated multiphase chemistry are key features to accurately evaluate climate and health impacts of secondary organic aerosol (SOA). However, today, the partitioning of oxygenated secondary species is rarely assessed in experimental SOA studies and SOA modelling is still largely based on estimated partitioning data. This paper describes a new analytical approach, solvent-free and easy to use, to explore the chemical composition of the secondary organic matter at a molecular scale in both gas and particulate phases. The method is based on thermal desorption (TD) of gas and particulate samples, coupled with gas chromatography (GC) and mass spectrometry (MS), with derivatisation on sampling supports. Gaseous compounds were trapped on Tenax TA adsorbent tubes pre-coated with pentafluorobenzylhydroxylamine (PFBHA) or N-Methyl-N-(t-butyldimethylsilyl)trifluoroacetamide (MTBSTFA). Particulate samples were collected onto quartz or Teflon-quartz filters and subsequently subjected to derivatisation with PFBHA or MTBSTFA before TD-GC/MS analysis. Method development and validation are presented for an atmospherically relevant range of organic acids and carbonyl and hydroxyl compounds. Application of the method to a limonene ozonolysis experiment conducted in the EUPHORE simulation chamber under simulated atmospheric conditions of low concentrations of limonene precursor and relative humidity, provides an overview of the method capabilities. Twenty-five compounds were positively or tentatively identified, nine being in both gaseous and particulate phases; and twelve, among them tricarboxylic acids, hydroxyl dicarboxylic acids and oxodicarboxylic acids, being detected for the first time.

This review focuses on the detection of diseased plants by analysis of volatile organic compound (VOC) emissions. It includes an overview of studies that report on the impact of infectious and noninfectious diseases on these emissions and discusses the specificity of disease-induced emissions. The review also provides an overview of processes that affect the gas balance of plant volatiles, including their loss processes. These processes are considered as important because they contribute to the time-dynamic concentration profiles of plant-emitted volatiles. In addition, we describe the most popular techniques currently in use to measure volatiles emitted from plants, with emphasis on agricultural application. Dynamic sampling coupled with gas chromatography and followed by an appropriate detector is considered as the most appropriate method for application in agriculture. It is recommended to evaluate the state-of-the-art in the fields concerned with this method and to explore the development of a new instrument based on the specific needs for application in agricultural practice. However, to apply such an instrument in agriculture remains a challenge, mainly due to high costs.

International audience; Secondary Organic Aerosols (SOAs) are formed in the atmosphere by gas-to-particle conversion of organic gases

The coadsorption of alkalis (K, Na) and CO on Cu(111) was investigated by high-resolution electron energy loss spectroscopy. Measurements performed at room temperature showed that CO adsorption is partially dissociative on a potassium-precovered Cu(111) surface and fully dissociative for Na/Cu(111). Carbon monoxide molecules occupy adsorption sites directly adjacent to those of alkali adatoms, as suggested by the absence of a threshold alkali precoverage for CO dissociation. On the contrary, for alkali+CO/Ni(111) a threshold alkali precoverage for CO dissociation was found to exist. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2996133]

The sticking probability for hydrogen on films of Co, Ni, Cu, Ru, Rh, Pd, Ir, and Pt supported on graphite has been measured at a hydrogen pressure of 1 bar in the temperature range 40–200 °C. The sticking probability is found to increase in the order Ni, Co, Ir, Pd, Pt, Rh, and Ru at temperatures below 150 °C, whereas at higher temperatures, the sticking probability for Pd is higher than for Pt. The sticking probability for Cu is below the detection limit of the measurement. The measured sticking probabilities are slightly lower than those obtained at high hydrogen coverage under ultrahigh vacuum conditions. This could be a consequence of the higher hydrogen pressure used here. The apparent desorption energies extracted from the steady-state desorption rate are found to agree reasonably well with published values for the heat of adsorption at high coverage. However, the sticking probability is not related in a simple way to published values for the heat of adsorption at low coverage, with Ru and Rh giving exceptionally high values for the sticking probability. It is suggested that this is due to the presence of adsorption sites with very low desorption energy on Ru and Rh. ©2008 American Institute of Physics.

A suitable method for the gas chromatographic determination of 10 characteristic carbonyls in biological and oil samples based on the in-drop formation of hydrazones by using 2,4,6-trichlorophenylhydrazine (TCPH), has been developed. The derivatisation-extraction procedure was optimized separately for aqueous and oil samples with respect to the appropriate organic drop solvent, drop volume, in-drop TCPH concentration, sample stirring rate, temperature during single-drop microextraction (SDME), reaction time and headspace-to-sample volume ratio. The optimization showed differentiation of optimum values between the studied matrices. The limits of detection were found to range from 0.001 to 0.003 mu g mL(-1) for the aqueous biological samples and from 0.06 to 0.20 mu g mL(-1) for the oil samples. The limits of quantification were in the range of 0.003-0.010 mu g mL(-1) and 0.020-0.059 mu g mL(-1) for aqueous and oil samples, respectively The overall relative standard deviations of the within-day repeatability and between-day reproducibility were < 4.4% and < 8.2% for the aqueous biological samples and < 3.9% and < 7.4% for the oxidized oil samples. (c) 2008 Elsevier B.V. All rights reserved. Analytica Chimica Acta

The dissociation and formation of water on the Rh(111) and Ni(111) surfaces have been studied using density functional theory with generalized gradient approximation and ultrasoft pseudopotentials. Calculations have been performed on 2x2 surface unit cells, corresponding to coverages of 0.25 ML, with spot checks on 3x3 surface unit cells (0.11 ML). On both surfaces, the authors find that water adsorbs flat on top of a surface atom, with binding energies of 0.35 and 0.25 eV, respectively, on Rh(111) and Ni(111), and is free to rotate in the surface plane. Barriers of 0.92 and 0.89 eV have to be overcome to dissociate the molecule into OH and H on the Rh(111) and Ni(111) surfaces, respectively. Further barriers of 1.03 and 0.97 eV need to be overcome to dissociate OH into O and H. The barriers for the formation of the OH molecule from isolated adsorbed O and H are found to be 1.1 and 1.3 eV, and the barriers for the formation of the water molecule from isolated adsorbed OH and H are 0.82 and 1.05 eV on the two surfaces. These barriers are found to vary very little as coverage is changed from 0.25 to 0.11 ML. The authors have also studied the dissociation of OH in the presence of coadsorbed H or O. The presence of a coadsorbed H atom only weakly affects the energy barriers, but the effect of O is significant, changing the dissociation barrier from 1.03 to 1.37 and 1.15 eV at 0.25 or 0.11 ML coverage on the Rh(111) surface. Finally, the authors have studied the dissociation of water in the presence of one O atom on Rh(111), at 0.11 ML coverage, and the authors find a barrier of 0.56 eV to dissociate the molecule into OH+OH. (c) 2007 American Institute of Physics.

This study deals with an automated data analysis strategy to pinpoint potential unknown compounds in full scan mass spectrometry (MS) experiments. Three examples of an untargeted metabolomics approach to contaminant analysis are given. By comparing a plant-oil based hormone cocktail to 90 plant oil samples ca. 25 compounds specific to the hormone cocktail could be detected. Five of these compounds were confirmed as steroid hormones. A comparison of a drink water sample from a farm to distillated water showed the presence of contaminants specific to this drink water sample. A grass sample, which was known to give a false positive result in a DR-CALUX bioassay, was unexpectedly shown to contain an abnormal level of chrysene, which was obviously not eliminated during clean-up.

The adsorption mechanism of alpha-sexithiophene (alpha-6T) on the clean Si(100)-(2x1) surface has been investigated using scanning tunneling microscopy (STM) and first principles electronic structure calculations. We find that at submonolayer coverage, the alpha-6T molecules are not stable and dissociate into monomers. We observe two different configurations of the monomers and have discussed the corresponding adsorption geometries based on theoretical calculations. The calculations elucidate how the fragments are absorbed on the surface, giving rise to the observed STM images. With increasing coverage, the STM images show the existence of complete alpha-6T molecules. In addition, results of the adsorption behavior of alpha-6T molecules on the H-passivated Si(100)-(2x1) surface are reported. On this surface the molecules are highly mobile at room temperature due to the weak molecule-substrate interaction. The STM results also indicate that they can easily be anchored at the defect sites.

The use of a programmed temperature vaporiser (PTV) with a packed liner was evaluated for the injection of large volumes (up to 100 mu l) of plasma extracts in a gas chromatograph. Solvent purity, which is essential when large volumes are injected into the GC system, was determined. Special attention was paid to the purity of the solvents used for the solid-phase extraction (SPE) procedure. For this SPE method, ethyl acetate was used as the extraction and reconstitution solvent, and thus the purity of the ethyl acetate was critical, especially when a non-selective GC detector was applied. The liquid capacity and inertness of different packed liners were investigated. The liner packed with ATAS "A" (modified Chromosorb-based material with special treatment) was found to be the most suitable for the analysis of the tested drugs. Good linearity in response for variations in volume and concentration was observed. A comparison was made between the applicability of flame ionisation detection (FID) and mass-selective detection (MSD). When 50-mu l volumes of plasma extracts were injected with the PTV, the detection limits for secobarbital, lidocaine, phenobarbital and diazepam were about 50-times lower than when 1-mu l volumes were injected. The detection limits of the tested compounds in plasma for injection of 50-100 mu l plasma extract are 5-10 ng/ml for GC-FID whereas plasma concentrations of 250 pg/ml can be detected using the selected ion monitoring (SUI) mode of a MSD. For non-selective GC-FID, the background from a 50-mu l injection was substantially larger than with 1-mu l injection as a result of co-injected plasma matrix components and solvent impurities. These background effects were less with GC-MSD in the total ion current mode and virtually absent with GC-MSD in the SIM mode. (C) 1999 Elsevier Science B.V. All rights reserved.

An analytical method based on TD-GC/MS was developed and validated for the determination of volatile organic compounds (VOCs), including linear and cyclic volatile methylsiloxanes (VMSs), in biogas. Biogas was first sampled in Supel (TM) Inert Film bags and subsequently dynamically sampled onto multisorbent bed tubes (Carbotrap, Carbopack X and Carboxen 569) using portable pump equipment. Two sample volumes, 100 and 250ml, were evaluated. Desorption efficiency values for both volumes are in the range of 99-100% for almost all studied compounds while breakthrough values (%VOC on sample tube back section) are below 1% for most evaluated VOCs. However, acetaldehyde, carbon disulphide, ethanol and 1,3-butadiene have breakthrough values higher than 5%. Method detection limits were in the range of 0.01-0.8 ng per sample. The most abundant VOCs in biogas were terpenes with concentrations between 500 and 700mgm(-3). Other important families were ketones, aromatic hydrocarbons and alkanes, with concentrations in the range of 36-46, 20-35 and 14-16mgm(-3), respectively. VMSs presented average concentrations of 4.9 +/- 0.4mgm(-3). Additionally, the Supel (TM) Inert Film bags were evaluated for stability for 4days at room temperature. Although several VOC families' concentrations in the bag increased or decreased significantly (t-test; p