Comprehensive Gas Chromatography-mass Spectrometry Research Articles

Comparison of head space solid phase micro extraction with conventional and comprehensive gas chromatography mass spectrometry for volatile profiling of Irish whiskey

Whiskey is a traditional distilled product produced on the island of Ireland that is currently experiencing a major expansion in export volume. Different styles of Irish whiskey exist, however only some very limited published information exists on the volatile congener profile of the different styles of Irish whiskey. Such information is potentially indispensable from a quality, flavour and authenticity perspective. As gas chromatography is the established analytical method of choice to identify volatile congeners, this study compared headspace-solid phase microextraction (HS-SPME) using conventional gas chromatography single quadrupole mass spectrometry, to HS-SPME and HS-SPME-Arrow using comprehensive two-dimensional gas chromatography (GC×GC) modulated using reverse flow in tandem with time-of-flight mass spectrometry (TOFMS) detection. Six representative Irish whiskey samples were evaluated consisting of new make spirit and mature whiskies representing Single Malts, Pot Stills and Blends. The number of volatile congeners identified in these samples by HS-SPME/HS-SPME Arrow GC×GC-TOFMS was approximately twice that detected by conventional HS-SPME GCMS. In total 145 unique individual volatile congeners, excluding ethanol were identified, with the majority consisting of esters, but also benzenes, alcohols, aldehydes, terpenoids, furans, ketones, alkanes, alkenes, norisoprenoids, acetals, acids, lactones and phenols. The use of HS-SPME Arrow GC×GC-TOFMS significantly enhances the number of volatile congeners that can be identified and therefore provides much more information that can convey insights into product quality, consistency, flavour and also for authentication purposes.

Gas Chromatography Mass Spectrometry (GC-MS) Analysis of lemongrass leaves: identification of bioactive compounds and their potential application

Lemongrass (Cymbopogon citratus) is a widely recognized aromatic herb which is popularly used in traditional medicine and culinary practices across the globe. This research study presents a comprehensive GC-MS analysis of lemongrass leaves, aimed to identify its bioactive compounds. The study explores the chemical composition of lemongrass leaves, focusing on potential applications in pharmaceutical, cosmetic and food industries. The analysis reveals various volatile and non-volatile compounds, shedding light on the therapeutic properties and potential commercial applications of this aromatic plant.

Volatile Compound Emissions from Stereolithography Three-Dimensional Printed Cured Resin Models for Biomedical Applications.

Stereolithography three-dimensional printing is used increasingly in biomedical applications to create components for use in healthcare and therapy. The exposure of patients to volatile organic compounds (VOCs) emitted from cured resins represents an element of concern in such applications. Here, we investigate the biocompatibility in relation to inhalation exposure of volatile emissions of three different cured commercial resins for use in printing a mouthpiece adapter for sampling exhaled breath. VOC emission rates were estimated based on direct analysis using a microchamber/thermal extractor coupled to a proton transfer reaction-mass spectrometer. Complementary analyses using comprehensive gas chromatography-mass spectrometry aided compound identification. Major VOCs emitted from the cured resins were associated with polymerization agents, additives, and postprocessing procedures and included alcohols, aldehydes, ketones, hydrocarbons, esters, and terpenes. Total VOC emissions from cubes printed using the general-purpose resin were approximately an order of magnitude higher than those of the cubes printed using resins dedicated to biomedical applications at the respective test temperatures (40 and 25 °C). Daily inhalation exposures were estimated and compared with daily tolerable intake levels or standard thresholds of toxicological concerns. The two resins intended for biomedical applications were deemed suitable for fabricating an adapter mouthpiece for use in breath research. The general-purpose resin was unsuitable, with daily inhalation exposures for breath sampling applications at 40 °C estimated at 310 μg day-1 for propylene glycol (tolerable intake (TI) limit of 190 μg day-1) and 1254 μg day-1 for methyl acrylate (TI of 43 μg day-1).

Changes in volatile compound profiles of cold-pressed berry seed oils induced by roasting

This study aimed to compare the volatile compounds of cold-pressed oils obtained from unroasted and roasted chokeberry, raspberry, blackcurrant, and strawberry seeds using comprehensive gas chromatography–mass spectrometry coupled to time of flight mass spectrometry (GC × GC-ToFMS). It is found that the seed type used and chemical composition affected the final aroma of berry oils. The volatile profiles of all berry oils from both unroasted and roasted seeds were dominated by nonheterocyclic chemical class (89% of the total volatiles) with esters predominant (32% of total nonheterocyclic compounds). Unroasted raspberry and blackcurrant cold-pressed seed oils had a less complex volatile profile, and showed similarities between them and differences to chokeberry and strawberry seed oils. Chokeberry seed oil was characterized by the highest levels in ethyl propanoate, methylbutyl acetate, benzaldehyde, (E,E)-2,4-decadienal, acetoin, 3-penten-2-one, benzyl alcohol and strawberry seed oil by methyl acetate, isobutyl acetate, methyl 2-methylbutanoate, ethyl 2-hydroxypropanoate, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, (E,E)-2,4-heptadienal, 1-penten-3-one, and 3,7-dimethyl-1,6-octadien-3-ol. N-containing and furanic-containing compounds contributed about 5% and 4%–16%, respectively, of total amount of volatiles after seed roasting. Roasting was critical for increasing the concentration of compounds derived from lipid peroxidation, especially in blackcurrant seed oils. Profiling volatiles using SPME-GC × GC-ToFMS might be helpful in evaluating oils quality.

Utilization of GC-MS untargeted metabolomics to assess the delayed response of glufosinate treatment of transgenic herbicide resistant (HR) buffalo grasses (Stenotaphrum secundatum L.).

Herbicide resistant (HR) buffalo grasses were genetically engineered to resist the non-selective herbicide, glufosinate in order to facilitate a modern, 'weeding program' which is highly effective in terms of minimizing costs and labor. The resistant trait was conferred by an insertion of the pat gene to allow for the production of the enzyme phosphinothricin acetyltransferase (PAT) to detoxify the glufosinate inhibitive effect. To date, there are only a few reports using metabolomics as well as molecular characterizations published for glufosinate-resistant crops with no reports on HR turfgrass. Therefore, for the first time, this study examines the metabolome of glufosinate-resistant buffalo grasses which not only will be useful to future growers but also the scientific community. A major aim of this present work is to characterize and evaluate the metabolic alterations which may arise from a genetic transformation of HR buffalo grasses by comprehensively using gas chromatography-mass spectrometry (GC-MS) based untargeted metabolomics. Eight-week old plants of 4 HR buffalo grasses, (93-1A, 93-2B, 93-3C and 93-5A) and 3 wild type varieties (WT 8-4A, WT 9-1B and WT 9-1B) were selected for physiological, molecular and metabolomics experiments. Plants were either sprayed with 1, 5, 10 and 15% v/v of glufosinate to evaluate the visual injuries or submerged in 5% v/v of glufosinate 3days prior to a GC-MS based untargeted metabolomics analysis. In contrast, the control group was treated with distilled water. Leaves were extracted in 1:1 methanol:water and then analysed, using an in-house GC-MS untargeted workflow. Results identified 199 metabolites with only 6 of them (cis-aconitic acid, allantoin, cellobiose, glyceric acid, maltose and octadecanoic acid) found to be statistically significant (p < 0.05) between the HR and wild type buffalo grass varieties compared to the control experiment. Among these metabolites, unusual accumulation of allantoin was prominent and was an unanticipated effect of the pat gene insertion. As expected, glufosinate treatment caused significant metabolic alterations in the sensitive wild type, with the up-regulation of several amino acids (e.g. phenylalanine and isoleucine) which was likely due to glufosinate-induced senescence. The aminoacyl-tRNA biosynthetic pathway was identified as the most significant enriched pathway as a result of glufosinate effects because a number of its intermediates were amino acids. HR buffalo grasses were very similar to its wild type comparator based on a comprehensive GC-MS based untargeted metabolomics and therefore, should guarantee the safe use of these HR buffalo grasses. The current metabolomics analyses not only confirmed the effects of glufosinate to up-regulate free amino acid pools in the sensitive wild type but also several alterations in sugar, sugar phosphate and organic acid metabolism have been reported.

Evaluating Novel Markers for Specimen Validity Testing.

Synthetic urine products are commercially marketed for the purpose of specimen substitution for urine drug screens. These products are widely popular because they yield negative drug screen results, meet criteria for specimen validity testing, and are easily accessible and affordable. Current specimen validity criteria are ineffective for detecting these synthetic products, and new markers of specimen validity are required. To develop and evaluate a multicomponent liquid chromatography tandem mass spectrometry (LC-MS/MS) assay for urine specimen validity testing. A quantitative LC-MS/MS assay was developed for caffeine, cotinine, theobromine, and urobilin in urine. The assay was applied to known synthetic urine products (n = 10) as well as human specimens received for pre-employment testing (n = 500), for-cause workplace testing (n = 100), and medical pain management monitoring (n = 200). Specimens devoid of all 4 validity markers were subjected to follow-up testing that involved microscopic urinalysis and comprehensive gas chromatography mass spectrometry for drugs, pharmaceuticals, hormones, and lipids. Of the experimental groups, 10 of 10 synthetic urine products (100%), 12 of 500 pre-employment specimens (2.4%), and 4 of 200 pain management specimens (2.0%) failed the experimental LC-MS/MS assay. Follow-up testing indicated that each of the failed specimens was nonphysiologic in nature. Simultaneous application of the 4 experimental validity markers appeared to be a robust method for detecting nonphysiologic specimens. New markers of specimen validity must be developed in order to identify commercially available synthetic urine products.

Toward the characterisation of non-intentionally added substances migrating from polyester-polyurethane lacquers by comprehensive gas chromatography-mass spectrometry technologies

Polyester-polyurethane lacquer, used to cover the inner surface of metallic food contact materials, may transfer non-intentionally added substances (NIAS) to the food. The identification of such a diversity of compounds, considered as migrating substances, requires taking advantage of complementary analytical platforms. Therefore, four types of gas chromatography-mass spectrometry (GCMS) couplings were investigated and compared for their abilities to identify migrating substances after acetonitrile extraction of two commercialised lacquers. In parallel, various ionisation sources, i.e. electron ionisation (EI) (70 eV and soft energies) and atmospheric-pressure chemical ionisation (APCI) as well as various mass analysers, i.e. quadrupole, time-of-flight (low and high resolution) and Orbitrap, were tested. Comparison of mass spectra with a commercial library for EI ionisation source led to the identification of two NIAS compounds, isophorone diisocyanate and 4,4′-diphenylmethane diisocyanate. Additionally, many cyclic oligoesters (four monomer units) were unambiguously identified according to supplier’s declaration on starting materials used, primarily based on the molecular ion observed by APCI mode and characteristic fragment ions. High resolution mass analysers also enhanced confidence level in such NIAS identification. One- and two-dimensional GC were also investigated for separation assessment. Although GC × GC did not reveal additional NIAS, its use provided a valuable mapping of oligomers according to monomers composition. These results were compared to our previously published LC–MS study, carried out on the same lacquer samples. This study shows that LC and GC, along with their related ionisation techniques and their own selectivity, are complementary approaches, revealing different classes of compounds covering a wide range of volatility and polarity.

Analysis of hydrogenation products of biocrude obtained from hydrothermally liquefied algal biomass by comprehensive gas chromatography mass spectrometry (GC×GC-MS)

Fuels produced from microalgae are a promising alternative for fuels from fossil resources. Algae biomass may be transformed by hydrothermal liquefaction (HTL) into biocrudes, which need upgrading by hydrotreatment to meet transportation fuel requirements.In this study, analyses of HTL biocrude catalytically hydrogenated in a batch reactor at temperatures between 360 and 400 °C and residence times between 2.5 and 10.2 h are presented. Selected samples were investigated by comprehensive gas chromatography mass spectrometry (GC×GC) using flame ionization (FID) or mass spectrometry (MS).The main components of the samples before and after the hydrogenation are hydrocarbons of different unsaturation including alkanes, alkenes, monocyclic and bicyclic hydrocarbons and monocyclic aromatic hydrocarbons. Also, small amounts of polyaromatic hydrocarbons are formed. The most frequent class of heteroatomic compounds are nitrogen and oxygen containing compounds. Oxygen containing compounds are primarily of phenolic nature, whilst nitrogen containing compounds show aromatic amine (alkylated aniline and isomers) and pyrrolic structures (alkylated indoles and carbazoles and isomers). Upon proceeding hydrogenation, an increasing content of lower molecular weight hydrocarbons is observed. The analyses allow to track the decrease of heteroatomic compounds and reveal the structure of refractory compounds. Ultimately, the results allow to identify optimum parameters for the hydrogenation of HTL biocrudes from algae, which correspond to a maximum yield of hydrocarbons and acceptable levels of heteroatomic compounds.

Exhaled human breath analysis in active pulmonary tuberculosis diagnostics by comprehensive gas chromatography-mass spectrometry and chemometric techniques

Tuberculosis (TB) is the deadliest infectious disease, and yet accurate diagnostics for the disease are unavailable for many subpopulations. In this study, we investigate the possibility of using human breath for the diagnosis of active TB among TB suspect patients, considering also several risk factors for TB for smokers and those with human immunodeficiency virus (HIV). The analysis of exhaled breath, as an alternative to sputum-dependent tests, has the potential to provide a simple, fast, non-invasive, and readily available diagnostic service that could positively change TB detection. A total of 50 individuals from a clinic in South Africa were included in this pilot study. Human breath has been investigated in the setting of active TB using the thermal desorption-comprehensive two-dimensional gas chromatography–time of flight mass spectrometry methodology and chemometric techniques. From the entire spectrum of volatile metabolites in breath, three machine learning algorithms (support vector machines, partial least squares discriminant analysis, and random forest) to select discriminatory volatile molecules that could potentially be useful for active TB diagnosis were employed. Random forest showed the best overall performance, with sensitivities of 0.82 and 1.00 and specificities of 0.92 and 0.60 in the training and test data respectively. Unsupervised analysis of the compounds implicated by these algorithms suggests that they provide important information to cluster active TB from other patients. These results suggest that developing a non-invasive diagnostic for active TB using patient breath is a potentially rich avenue of research, including among patients with HIV comorbidities.

Metabonomics Profiling Reveals Biochemical Pathways Associated with Pulmonary Arterial Hypertension in Broiler Chickens.

Pulmonary arterial hypertension (PAH) is the major cause of death in fast growing meat-type chickens (broiler chickens). At present, the underlying mechanisms that give rise to PAH are not fully understood. To identify the metabonomics profiles characterizing the process, we conducted a comprehensive gas chromatography-mass spectrometry (GC-MS)-based metabolic profiling of lung tissues from PAH broilers and age-matched controls. PAH was induced by excess salt in drinking water. Medial hypertrophy of pulmonary arteries was present in PAH birds as compared with controls. The metabonomics profiles of lung tissues well distinguished PAH broilers from control subjects. Significant changes in the levels of 41 metabolites were detected in PAH vs normal birds. Aside from the metabolic alterations indicating a status of oxidative stress and inflammation, evidence of reduced cellular uptake of arginine due to increased lysine biosynthesis and of a shift of arginine metabolism to arginase pathway were observed. In addition, PAH birds showed increased biosynthesis of fatty acids, which may be associated with excessive proliferation of vascular cells during pulmonary vascular remodeling. Furthermore, we observed significant changes in pentose phosphate pathway and increased aminomalonic acid in PAH broilers. These results provide additional biochemical insights into the pathogenesis of the PAH. Our data may lead to the development of new strategies to control PAH in broilers.

Metabolomic Evaluation of the Quality of Leaf Lettuce Grown in Practical Plant Factory to Capture Metabolite Signature.

Vegetables produce metabolites that affect their taste and nutritional value and compounds that contribute to human health. The quality of vegetables grown in plant factories under hydroponic cultivation, e.g., their sweetness and softness, can be improved by controlling growth factors including the temperature, humidity, light source, and fertilizer. However, soil is cheaper than hydroponic cultivation and the visual phenotype of vegetables grown under the two conditions is different. As it is not clear whether their metabolite composition is also different, we studied leaf lettuce raised under the hydroponic condition in practical plant factory and strictly controlled soil condition. We chose two representative cultivars, “black rose” (BR) and “red fire” (RF) because they are of high economic value. Metabolite profiling by comprehensive gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS) resulted in the annotation of 101 metabolites from 223 peaks detected by GC-MS; LC-MS yielded 95 peaks. The principal component analysis (PCA) scatter plot showed that the most distinct separation patterns on the first principal component (PC1) coincided with differences in the cultivation methods. There were no clear separations related to cultivar differences in the plot. PC1 loading revealed the discriminant metabolites for each cultivation method. The level of amino acids such as lysine, phenylalanine, tryptophan, and valine was significantly increased in hydroponically grown leaf lettuce, while soil-cultivation derived leaf lettuce samples contained significantly higher levels of fatty-acid derived alcohols (tetracosanol and hexacosanol) and lettuce-specific sesquiterpene lactones (lactucopicrin-15-oxalate and 15-deoxylactucin-8-sulfate). These findings suggest that the metabolite composition of leaf lettuce is primarily affected by its cultivation condition. As the discriminant metabolites reveal important factors that contribute to the nutritional value and taste characteristics of leaf lettuce, we performed comprehensive metabolite profiling to identify metabolite compositions, i.e., metabolite signature, that directly improve its quality and value.

Chemical Analysis and Simulated Pyrolysis of Tobacco Heating System 2.2 Compared to Conventional Cigarettes.

Tobacco Heating System 2.2 (THS 2.2, marketed as iQOS) is a heat-not-burn (HNB) tobacco product that has been successfully introduced to global markets. Despite its expanding market, few independent and systematic researches into THS 2.2 have been carried out to date. We tested a comprehensive list of total particulate matter (TPM), water, tar, nicotine, propylene glycol, glycerin, carbon monoxide, volatile organic compounds, aromatic amines, hydrogen cyanide, ammonia, N-nitrosamines, phenol, and polycyclic aromatic hydrocarbon under both ISO and HCI regimes. We also simulated pyrolysis of THS 2.2 heating sticks and made comparisons with conventional cigarette tobacco fillers using comprehensive gas chromatography-mass spectrometry (GC × GC-MS) to determine whether the specially designed ingredients help reduce harmful constituents. Other than some carbonyls, ammonia, and N-nitrosoanabasine (NAB), the delivered releases from THS 2.2 were at least 80% lower than those from 3R4F. Tar and nicotine remained almost the same as 3R4F. Interestingly, the normalized yield of THS 2.2 to 3R4F under the HCI regime was lower than that under the ISO regime. THS 2.2 delivered fewer harmful constituents than the conventional cigarette 3R4F. Simulated pyrolysis results showed that the lower temperature instead of specially designed ingredients contributed to the distinct shift. In particular, if smoking machines are involved to evaluate the HNB products, smoking regimes of heat-not-burn tobacco products should be carefully chosen. To our knowledge, few independent studies of HNB products have been published. In this paper, a comprehensive list of chemical releases was tested systematically and compared to those from 3R4F. Although THS 2.2 generates lower levels of harmful constituents, the nicotine and tar levels were almost identical to 3R4F.The results should be discussed carefully in the future when assessing the dual-use with other conventional cigarettes, nicotine dependence of HNB products, etc. This study also suggests that regulatory agencies should pay attention to the smoking regimes that are adopted to evaluate HNB tobacco products.

Analysis of pyrolysis liquids obtained from the slow pyrolysis of a German brown coal by comprehensive gas chromatography mass spectrometry

Due to the upcoming shortage of crude oil and natural gas, alternative resources for the production of chemicals are needed and long-term research should be conducted. One of the future possible methods for the production of valuable chemicals is the utilization of coal and its conversion by pyrolysis. During pyrolysis, macromolecular organic compounds are decomposed into smaller compounds, which can be utilized. The development of these processes requires compositional knowledge of the products, which are very complex mixtures of organic compounds. In this study a series of pyrolysis liquids obtained in a fixed bed reactor at different pyrolysis temperatures between 400 and 700°C is analyzed qualitatively and quantitatively by comprehensive gas chromatography mass spectrometry (GC×GC-MS). More than thousand compounds were observed in each of the samples. Selected compound classes (alkanes, alkenes, alkylbenzenes, phenols, carboxylic acids and thiophenes) are discussed in detail. Quantification results of 94 compounds are given, visualized and discussed in relation to the pyrolysis conditions. It is demonstrated, that the application of GC×GC-MS is highly beneficial for the analysis of pyrolysis liquids from coal.

Automated resolution of chromatographic signals by independent component analysis–orthogonal signal deconvolution in comprehensive gas chromatography/mass spectrometry-based metabolomics

Comprehensive gas chromatography–mass spectrometry (GC×GC–MS) provides a different perspective in metabolomics profiling of samples. However, algorithms for GC×GC–MS data processing are needed in order to automatically process the data and extract the purest information about the compounds appearing in complex biological samples. This study shows the capability of independent component analysis–orthogonal signal deconvolution (ICA–OSD), an algorithm based on blind source separation and distributed in an R package called osd, to extract the spectra of the compounds appearing in GC×GC–MS chromatograms in an automated manner. We studied the performance of ICA–OSD by the quantification of 38 metabolites through a set of 20 Jurkat cell samples analyzed by GC×GC–MS. The quantification by ICA–OSD was compared with a supervised quantification by selective ions, and most of the R2 coefficients of determination were in good agreement (R2>0.90) while up to 24 cases exhibited an excellent linear relation (R2>0.95). We concluded that ICA–OSD can be used to resolve co-eluted compounds in GC×GC–MS.

Flavoromics approach in monitoring changes in volatile compounds of virgin rapeseed oil caused by seed roasting

Two varieties of rapeseed (one high oleic – containing 76% of oleic acid, and the other – containing 62% of oleic acid) were used to produce virgin (pressed) oil. The rapeseeds were roasted at different temperature/time combinations (at 140–180°C, and for 5–15min); subsequently, oil was pressed from the roasted seeds. The roasting improved the flavour and contributed to a substantial increase in the amount of a potent antioxidant–canolol. The changes in volatile compounds related to roasting conditions were monitored using comprehensive gas chromatography–mass spectrometry (GC×GC-ToFMS), and the key odorants for the non-roasted and roasted seeds oils were determined by gas chromatography–olfactometry (GC-O). The most important compounds determining the flavour of oils obtained from the roasted seeds were dimethyl sulphide, dimethyltrisulfide, 2,3-diethyl-5-methylpyrazine, 2,3-butenedione, octanal, 3-isopropyl-2-methoxypyrazine and phenylacetaldehyde. For the oils obtained from the non-roasted seeds, the dominant compounds were dimethylsulfide, hexanal and octanal. Based on GC×GC-ToFMS and principal component analysis (PCA) of the data, several compounds were identified that were associated with roasting at the highest temperatures regardless of the rapeseed variety: these were, among others, methyl ketones (2-hexanone, 2-heptanone and 2-octanone).

Analysis of pyrolysis liquid obtained from whole tyre pyrolysis with molten zinc as the heat transfer media using comprehensive gas chromatography mass spectrometry

Pyrolysis of scrap tyres is a promising technology to recover valuable materials such as pyrolysis liquids, carbon black and steel. Pyrolysis liquids are complex mixtures of organic compounds and may represent a valuable source for chemicals. And because pyrolysis liquids are complex mixtures, high resolution analytical methods are required to accurately characterize these liquids. In this study comprehensive gas chromatography mass spectrometry (GC×GC–MS) using a reversed column setup (polar×apolar) was used for the analysis of a pyrolysis liquid. The tyre pyrolysis liquid analyzed was obtained from a process which places whole tyres onto molten zinc (460–480°C) providing direct heat transfer and hence rapid pyrolysis. The results show, that the pyrolysis liquid is a complex mixture of acyclic and cyclic, aliphatic, unsaturated and aromatic hydrocarbons and several heteroatomic compounds. Compared to a normal column setup (apolar×polar), the reversed column setup separates structurally similar acyclic and cyclic hydrocarbon compounds with different degree of unsaturation better. A quantification was performed for a set of 40 compounds. A qualitative and quantitative evaluation of the compounds found, that the composition of the pyrolysis liquid is typical for tyre pyrolysis liquids. Nevertheless, comparably high amounts of limonene of 6.6% (w/w) and low amounts of monocyclic aromatic compounds were found. This is attributed to the very high heating rate of this process due to the direct heat contact of the tyres with molten zinc.

Comparison of enzymatic and acid hydrolysis of bound flavor compounds in model system and grapes

Four synthesized terpenyl-ß-d-glycopyranosides (geranyl, neryl, citronellyl, myrtenyl) were subjected to enzymatic (AR 2000, pH 5.5) and acid (citric buffer, pH 2.5) hydrolysis. Decrease of glycosides was measured by HPLC and the volatiles released – by comprehensive gas chromatography–mass spectrometry (GC×GC–ToF-MS). Enzymatic hydrolysis performed for 21h yielded 100% degree of hydrolysis for all glycosides but citronellyl (97%). Degree of acid hydrolysis was highly dependent on type of aglycone and the conditions. The highest degree was achieved for geraniol, followed by citronellol and nerol. Myrtenylo-ß-d-glycopyranoside was the most resistant glycoside to hydrolysis. Acid hydrolysis degree was also related to temperature/time combination, the highest being for 100°C and 2h. In a result of enzymatic hydrolysis 85–91% of total peak areas was terpene aglycone, whereas for acid hydrolysis the area of released terpene aglycone did not exceed 1.3% of total peak area indicating almost complete decomposition/transformation of terpenyl aglycone.

Monitoring of atmospheric gaseous and particulate polycyclic aromatic hydrocarbons in South African platinum mines utilising portable denuder sampling with analysis by thermal desorption–comprehensive gas chromatography–mass spectrometry

Concentrations of diesel particulate matter and polycyclic aromatic hydrocarbons (PAHs) in platinum mine environments are likely to be higher than in ambient air due to the use of diesel machinery in confined environments. Airborne PAHs may be present in gaseous or particle phases each of which has different human health impacts due to their ultimate fate in the body. Here we report on the simultaneous sampling of both phases of airborne PAHs for the first time in underground platinum mines in South Africa, which was made possible by employing small, portable denuder sampling devices consisting of two polydimethylsiloxane (PDMS) multi-channel traps connected in series separated by a quartz fibre filter, which only require small, battery operated portable personal sampling pumps for air sampling. Thermal desorption coupled with comprehensive gas chromatography–mass spectrometry (TD–GC×GC–TofMS) was used to analyse denuder samples taken in three different platinum mines. The samples from a range of underground environments revealed that PAHs were predominantly found in the gas phase with naphthalene and mono-methylated naphthalene derivatives being detected at the highest concentrations ranging from 0.01 to 18μgm−3. The particle bound PAHs were found in the highest concentrations at the idling load haul dump vehicle exhausts with a dominance of fluoranthene and pyrene. Particle associated PAH concentrations ranged from 0.47 to 260ngm−3 and included benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene and benzo[ghi]perylene. This work highlights the need to characterise both phases in order to assess occupational exposure to PAHs in this challenging sampling environment.

Detection of multiple steroidal compounds in synthetic urine using comprehensive gas chromatography-mass spectrometry (GC×GC-MS) combined with a molecularly imprinted polymer clean-up protocol.

A method capable of screening for multiple steroids in urine has been developed, using a series of twelve structurally similar, and commercially relevant compounds as target analytes. A molecularly imprinted solid phase extraction clean-up step was used to make the sample suitable for injection onto a GC×GC-MS setup. Significant improvements compared to a commercially available C-18 material were observed. Each individual steroid was able to be separated and identified, using both the retention profile and diagnostic fragmentation ion monitoring abilities of the comprehensive chromatographic-mass spectrometry method. Effective LODs of between 11.7 and 27.0 pg were calculated for individual steroids, effectively equivalent to concentration levels of between 0.234 and 0.540 ng mL(-1) in urine, while the application of multiple screen was demonstrated using a 10 ng mL(-1) mixed sample. The nature of this study also removes the need for sample derivitisation which speeds up the screening process.

Alkylbenzene Analysis in Pyrolysis Oils from Biomass and Coal by Comprehensive Gas Chromatography Mass Spectrometry

AbstractElf Einsatzstoffe entlang der Inkohlungsreihe wurden in einem Festbettreaktor pyrolysiert und die Ausbeuten der gasförmigen, flüssigen und festen Produkte bestimmt. Die gewonnenen Pyrolyseöle wurden hinsichtlich der Alkylbenzole mit komprehensiver Gaschromatographie‐Massenspektrometrie qualitativ untersucht. In allen Proben, von Biomasse bis Anthrazit, konnten leichte Alkylbenzole nachgewiesen werden. In kohlestämmigen Pyrolyseölen konnten darüber hinaus langkettig substituierte n‐Alkylbenzole gefunden und eine deutlich erhöhte Anzahl an Isomeren bei gegebener Summenformel nachgewiesen werden.