Volatile sampling by headspace techniques Soria, A.C.; García-Sarrió, M.J.; Sanz, M.L.
TrAC, Trends in analytical chemistry (Regular ed.),
09/2015, Letnik:
71
Journal Article
Recenzirano
•We comprehensively review static and dynamic headspace (HS) for volatile extraction.•The most recent advances on instrumentation are covered.•Critical discussion on the most outstanding applications ...in different fields.•Non-separative headspace coupled to mass spectrometry (HS-MS).•Headspace sampling is a simple, green method for volatile fractionation.
We review the use of static headspace (S-HS) and dynamic headspace (D-HS) techniques for the extraction of volatiles from different matrices. We present fundamentals and the most relevant advances in instrumentation, together with detailed discussion on the most important parameters affecting HS sampling. We also describe some of the most recent and outstanding applications, classified according to the type of matrix – among them, the use of ionic liquids as solvents for S-HS, the coupling of D-HS to comprehensive two-dimensional gas chromatography, the development of novel miniaturized devices for D-HS sampling and increasing interest in approaches based on HS-mass spectrometry (HS-MS) for fast, unbiased sample classification. We also review multi-step strategies for accurate quantitation of volatiles in samples with noticeable matrix effects. To conclude, we show that HS sampling is a versatile, rapid, efficient, green technique for volatile extraction, free of interferences.
•We give explicit expressions for the HS-splitting fields of abelian mixed Cayley graphs. In addition, we derive a formula to calculate their corresponding HS-algebraic degrees. Moreover, we ...characterize all HS-integral abelian mixed Cayley graphs.•The method we used involving much mathematics.
For an n-vertex mixed graph A, let HS(A) be the Hermitian-adjacency matrix of the second kind of A and ΦA(HS,λ)=det(λIn−HS(A)) the characteristic polynomial of HS(A). The splitting field of ΦA(HS,λ) is referred to as the HS-splitting field of A. Its extension degree over the rational number field Q is referred to as the HS-algebraic degree of A, and A is said to be HS-integral if all eigenvalues of HS(A) are integers. In this paper, we give explicit expressions for the HS-splitting fields of abelian mixed Cayley graphs. In addition, we derive a formula to calculate their corresponding HS-algebraic degrees. Moreover, we characterize all HS-integral abelian mixed Cayley graphs.
The study of ionized gas morphology and kinematics in nine extremely metal-deficient (XMD) galaxies with the scanning Fabry–Perot interferometer on the Special Astrophysical Observatory (SAO) 6-m ...telescope is presented. Some of these very rare objects (with currently known range of O/H of 7.12 < 12 + log(O/H) < 7.65, or ) are believed to be the best proxies of ‘young’ low-mass galaxies in the high-redshift Universe. One of the main goals of this study is to look for possible evidence of star formation (SF) activity induced by external perturbations. Recent results from H i mapping of a small subsample of XMD star-forming galaxies provided confident evidence for the important role of interaction-induced SF. Our observations provide complementary or new information that the great majority of the studied XMD dwarfs have strongly disturbed gas morphology and kinematics or the presence of detached components. We approximate the observed velocity fields by simple models of a rotating tilted thin disc, which allows us the robust detection of non-circular gas motions. These data, in turn, indicate the important role of current/recent interactions and mergers in the observed enhanced SF. As a by-product of our observations, we obtained data for two Low Surface Brightness (LSB) dwarf galaxies: Anon J012544+075957 that is a companion of the merger system UGC 993, and SAO 0822+3545 which shows off-centre, asymmetric, low star formation rate star-forming regions, likely induced by the interaction with the companion XMD dwarf HS 0822+3542.
Aims.We report the discovery of five new dwarf novae that were spectroscopically identified in the Hamburg Quasar Survey (HQS), and discuss the properties of the sample of new dwarf novae from the ...HQS. Methods.Follow-up time-resolved spectroscopy and photometry have been obtained to characterise the new systems. Results.The orbital periods determined from analyses of the radial velocity variations and/or orbital photometric variability are Porb min or Porb min for HS 0417+7445, Porb min for HS 1016+3412, Porb min for HS 1340+1524, Porb min for HS 1857+7127, and Porb min for HS 2214+2845. HS 1857+7127 is found to be partially eclipsing. In HS 2214+2845 the secondary star of spectral type $\rm M3\pm1$ is clearly detected, and we estimate the distance to the system to be $d=390\pm40$ pc. We recorded one superoutburst of HS 0417+7445, identifying the system as a SU UMa-type dwarf nova. HS 1016+3412 and HS 1340+1524 have rare outbursts, and their subtype is yet undetermined. HS 1857+7127 frequently varies in brightness and may be a Z Cam-type dwarf nova. HS 2214+2845 is a U Gem-type dwarf nova with a most likely cycle length of 71 d. Conclusions.To date, 14 new dwarf novae have been identified in the HQS. The ratio of short-period (<3 h) to long-period (>3 h) systems of this sample is 1.3, much smaller compared to the ratio of 2.7 found for all known dwarf novae. The HQS dwarf novae display typically infrequent or low-amplitude outburst activity, underlining the strength of spectroscopic selection in identifying new CVs independently of their variability. The spectroscopic properties of short-period CVs in the HQS, newly identified and previously known, suggest that most, or possibly all of them are still evolving towards the minimum period. Their total number agrees with the predictions of population models within an order of magnitude. However, the bulk of all CVs is predicted to have evolved past the minimum period, and those systems remain unidentified. This suggests that those post-bounce systems have markedly weaker Hβ emission lines compared to the average known short-period CVs, and undergo no or extremely rare outbursts.
Summary
Coconut oil has been extensively used in the food industry, but determination of the quality of coconut oil remains challenging. In this study, volatile components of the coconut oils ...(refined, desiccated or virgin) subjected to different processing methods were identified and compared. Twenty‐six volatile components exhibiting characteristic differences among the three types of coconut oil were screened using headspace solid‐phase microextraction–gas chromatography–mass spectrometry (HS‐SPME‐GC‐MS). Furthermore, ethanol, 1‐propanol and dimethyl ketone could only be determined by using headspace‐gas chromatography–ion mobility spectrometry (HS‐GC‐IMS). The principal component analysis diagrams attained by the volatile component data demonstrated that the coconut oil samples could be clearly classified into three categories. The multivariate analysis results revealed 2‐heptanone and hexanal to be the most promising markers in terms of grade discrimination in coconut oil. The findings are conducive to the development of a new method for the identification of oils with different refining degrees.
Characterisation and classification of volatiles from coconut oil by HS‐SPME‐GC‐MS and HS‐SPME‐GC‐IMS coupled with an appropriate multivariate analysis have the potential to be used as a non‐destructive way to evaluate coconut oil quality and any other characteristics.
The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using ...headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (
E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.
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•115 kinds of VOCs were identified and most of them were accumulated during the pile fermentation.•Most of alcohols and acids decreased while esters and pyrazines increased during ...fermentation.•Hexanol, hexanal and 2-pentylfuran might be responsible for the odors of unfermented black beans.•Esters and pyrazine (e.g. ethyl acetate) contributed to the aroma of matured Douchi.
The present study investigates volatile organic compound (VOC) compositional changes in Liuyang Douchi during fermentation via a HS-GC-IMS and HS-SPME-GC-MS combination approach. A total of 115 VOCs were identified from Douchi, most of which were accumulated during pile fermentation. Notably, most alcohols and acids decreased with fermentation, while esters, ketones, pyrazines, and phenols accumulated during pile fermentation. Depending on the VOCs identified by GC-IMS/MS, the different fermentation stages of Douchi could be facilely distinguished. Of these, 49 VOCs were regarded as the marker VOCs of Douchi in different fermentation stage: hexanol, hexanal, and propanoic acid was the marker VOCs of the black beans before fermentation and contributing beany and grassy odors; 1-octen-3-ol and 3-octanone supplying a mushroom aroma to the Douchi fermented for 3–9 days; and esters and pyrazine, especially ethyl acetate and 2,6-dimethylpyrazine, contributing the cocoa, fruity, and nutty aromas of matured Douchi.
Fraudulent acts regarding honey authenticity that use Apis mellifera honey as a substitute for Apis cerana honey have garnered considerable concern in China and triggered a trust crisis from ...consumers. In this study, untargeted metabolomics analysis was carried out based on volatile fractions in honey from A. cerana and A. mellifera using headspace gas chromatography–ion mobility spectrometry (HS-GC-IMS). Honey from A. cerana and A. mellifera was discriminated by HS-GC-IMS profiling, principal component analysis, and orthogonal partial least-squares discrimination analysis. Tentative markers were identified from p-values and the variable importance in projection analysis and confirmed using the retention index, mass fragments, and reference standards by gas chromatography–mass spectrometry (GC–MS). A targeted method was established using the headspace solid phase coupled with microextraction GC–MS (HS-SPME-GC–MS) to quantitate the markers. The results demonstrated that the developed untargeted and targeted metabolomics approach performed well when discriminating honey from A. cerana and A. mellifera.
Most patients with non-lesional temporal lobe epilepsy (NLTLE) will have the findings of hippocampal sclerosis (HS) on a high resolution MRI. However, a significant minority of patients with NLTLE ...and electroclinically well-lateralized temporal lobe seizures have no evidence of HS on MRI. Many of these patients have concordant hypometabolism on fluorodeoxyglucose-PET (18FFDG-PET). The pathophysiological basis of this latter group remains uncertain. We aimed to determine whether NLTLE without HS on MRI represents a variant of or a different clinicopathological syndrome from that of NLTLE with HS on MRI. The clinical, EEG, 18FFDG-PET, histopathological and surgical outcomes of 30 consecutive NLTLE patients with well-lateralized EEG but without HS on MRI (HS−ve TLE) were compared with 30 consecutive age- and sex-matched NLTLE patients with well-lateralized EEG with HS on MRI (HS+ve TLE). Both the HS+ve TLE group and the HS−ve TLE patients had a high degree of 18FFDG-PET concordant lateralization (26 out of 30 HS−ve TLE versus 27 out of 27 HS+ve TLE). HS−ve TLE patients had more widespread hypometabolism on 18FFDG-PET by blinded visual analysis odds ratio (OR = +∞ (2.51, −), P = 0.001. The HS−ve TLE group less frequently had a history of febrile convulsions OR = 0.077 (0.002–0.512), P = 0.002, more commonly had a delta rhythm at ictal onset OR = 3.67 (0.97–20.47), P = 0.057, and less frequently had histopathological evidence of HS OR = 0 (0–0.85), P = 0.031. There was no significant difference in surgical outcome despite half of those without HS having a hippocampal-sparing procedure. Based on the findings outlined, HS−ve PET-positive TLE may be a surgically remediable syndrome distinct from HS+ve TLE, with a pathophysiological basis that primarily involves lateral temporal neocortical rather than mesial temporal structures.
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•Variations could be presented overall in the combination of three techniques.•Finger citron samples at different pickling stages could be distinguished.•Salting and drying had the ...greatest effect on volatile components of finger citron.•The characteristic flavor components were formed during salting and drying steps.
The pickled products of finger citron are famous in southern China for their unique taste and flavor. Although pickling process involves complex treatments including salting, desalting, sugaring, cooking and drying, extended shelf-life up to ten years after pickling can be achieved. In this study, the variations of volatile flavour components in the pickling process of finger citron were investigated by electronic nose (E-nose), headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). HS-SPME-GC-MS identified 85 substances, and HS-GC-IMS identified 81 substances, including terpenoids (21), aromatic hydrocarbons (11), alcohols (11), aldehydes (10), esters (7), phenols (6), acids (5), ethers (2), ketones (2), and other species (10). Linalool, limonene, (E)-3,7-dimethyl-1,3,6-octatriene, myrcene, 3-carene, β-pinene, α-pinene, terpinolene, 1-methyl-4-(1-methylethyl)-1,4-cyclohexadiene, α-terpinene, (S)-β-bisabolene, 1-isopropyl-2-methylbenzene and 1-methyl-4-(1-methylethenyl)-benzene were the stable substances at relatively high contents in finger citron at different pickling process. Salting and drying steps in the pickling process exerted greatest influence on the volatile components of finger citron. Salting promoted the generation of aldehydes, esters and acids, but led to the disappearance of alcohols, while drying promoted the generation of alcohols, phenols, aldehydes and acids at the expense of reduction in terpenoids. Our study revealed that the characteristic volatile compounds of finger citron pickled products was mainly formed by the biological reactions in the salting stage and thermal chemical transformations in the drying stage. This study also validated the suitability of E-nose combined with HS-SPME-GC-MS and HS-GC-IMS in tracking the changes of volatile components in finger citron during the pickling process.
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