Metabolite profiling of Piper longum L. fruit volatiles by two-dimensional gas chromatography and time-of-flight mass spectrometry: Insights into the chemical complexity.

Piper longum L. (long pepper) is an economically and industrially important medicinal plant. However, the characterization of its volatiles has only been analyzed by gas chromatography-mass spectrometry (GC-MS). In the present study, precise characterization of P. longum fruit volatiles has been performed for the first time through advanced two-dimensional gas chromatography-time-of-flight spectrometry (GC×GC-TOFMS). A total of 146 constituents accounting for 93.79% were identified, of which 30 were reported for the first time. All these constituents were classified into alcohols (4.5%), alkanes (8.9%), alkenes (6.71%), esters (6.15%), ketones (0.58%), monoterpene hydrocarbons (1.64%), oxygenated monoterpenes (2.24%), sesquiterpene hydrocarbons (49.61%), oxygenated sesquiterpenes (13.03%), phenylpropanoid (0.23%), and diterpenes (0.2%). Among all the classes, sesquiterpene hydrocarbons were abundant, with germacrene-D (2.87% ± 0.01%) as the major one, followed by 8-heptadecene (2.69% ± 0.03%), ß-caryophyllene (2.43% ± 0.03%), n-heptadecane (2.4% ± 0.04%), n-pentadecane (2.11% ± 0.05%), and so forth. Further, 20 constituents were observed to be coeluted and separated precisely in the two-dimensional column. The investigation provides an extensive metabolite profiling of P. longum fruit volatiles, which could be helpful to improve its therapeutic potential.

GC × GC-TOFMS metabolomics analysis identifies elevated levels of plasma sugars and sugar alcohols in diabetic mellitus patients with kidney failure.

Two dimensional GC (GC × GC)-time-of-flight mass spectrometry (TOFMS) has been used to improve accurate metabolite identification in the chemical industry, but this method has not been applied as readily in biomedical research. Here, we evaluated and validated the performance of high resolution GC × GC-TOFMS against that of GC-TOFMS for metabolomics analysis of two different plasma matrices, from healthy controls (CON) and diabetes mellitus (DM) patients with kidney failure (DM with KF). We found GC × GC-TOFMS outperformed traditional GC-TOFMS in terms of separation performance and metabolite coverage. Several metabolites from both the CON and DM with KF matrices, such as carbohydrates and carbohydrate-conjugate metabolites, were exclusively detected using GC × GC-TOFMS. Additionally, we applied this method to characterize significant metabolites in the DM with KF group, with focused analysis of four metabolite groups: sugars, sugar alcohols, amino acids, and free fatty acids. Our plasma metabolomics results revealed 35 significant metabolites (12 unique and 23 concentration-dependent metabolites) in the DM with KF group, as compared with those in the CON and DM groups (N = 20 for each group). Interestingly, we determined 17 of the 35 (14/17 verified with reference standards) significant metabolites identified from both the analyses were metabolites from the sugar and sugar alcohol groups, with significantly higher concentrations in the DM with KF group than in the CON and DM groups. Enrichment analysis of these 14 metabolites also revealed that alterations in galactose metabolism and the polyol pathway are related to DM with KF. Overall, our application of GC × GC-TOFMS identified key metabolites in complex plasma matrices.

Comprehensive Insight into Colorectal Cancer Metabolites and Lipids for Human Serum: A Proof-of-Concept Study.

Colorectal cancer (CRC) ranks as the third most frequently diagnosed cancer and the second leading cause of cancer-related deaths. The current endoscopic-based or stool-based diagnostic techniques are either highly invasive or lack sufficient sensitivity. Thus, there is a need for less invasive and more sensitive screening approaches. We, therefore, conducted a study on 64 human serum samples representing three different groups (adenocarcinoma, adenoma, and control) using cutting-edge GC×GC-LR/HR-TOFMS (comprehensive two-dimensional gas chromatography coupled with low/high-resolution time-of-flight mass spectrometry). We analyzed samples with two different specifically tailored sample preparation approaches for lipidomics (fatty acids) (25 µL serum) and metabolomics (50 µL serum). In-depth chemometric screening with supervised and unsupervised approaches and metabolic pathway analysis were applied to both datasets. A lipidomics study revealed that specific PUFA (ω-3) molecules are inversely associated with increased odds of CRC, while some PUFA (ω-6) analytes show a positive correlation. The metabolomics approach revealed downregulation of amino acids (alanine, glutamate, methionine, threonine, tyrosine, and valine) and myo-inositol in CRC, while 3-hydroxybutyrate levels were increased. This unique study provides comprehensive insight into molecular-level changes associated with CRC and allows for a comparison of the efficiency of two different analytical approaches for CRC screening using same serum samples and single instrumentation.

Exploring the Aroma Fingerprint of Various Chinese Pear Cultivars through Qualitative and Quantitative Analysis of Volatile Compounds Using HS-SPME and GC×GC-TOFMS.

To comprehensively understand the volatile compounds and assess the aroma profiles of different types of Pyrus ussuriensis Maxim. Anli, Dongmili, Huagai, Jianbali, Jingbaili, Jinxiangshui, and Nanguoli were detected via headspace solid phase microextraction (HS-SPME) coupled with two-dimensional gas chromatography/time-of-flight mass spectrometry (GC×GC-TOFMS). The aroma composition, total aroma content, proportion and number of different aroma types, and the relative quantities of each compound were analyzed and evaluated. The results showed that 174 volatile aroma compounds were detected in various cultivars, mainly including esters, alcohols, aldehydes, and alkenes: Jinxiangshui had the highest total aroma content at 2825.59 ng/g; and Nanguoli had the highest number of aroma species detected at 108. The aroma composition and content varied among pear varieties, and the pears could be divided into three groups based on principal component analysis. Twenty-four kinds of aroma scents were detected; among them, fruit and aliphatic were the main fragrance types. The proportions of aroma types also varied among different varieties, visually and quantitatively displaying changes of the whole aroma of the different varieties of pears brought by the changes in aroma composition. This study contributes to further research on volatile compound analysis, and provides useful data for the improvement of fruit sensory quality and breeding work.

Antibacterial Activity and Untargeted Metabolomics Profiling of Acalypha arvensis Poepp.

The search for potent antimicrobial compounds is critical in the face of growing antibiotic resistance. This study explores Acalypha arvensis Poepp. (A. arvensis), a Caribbean plant traditionally used for disease treatment. The dried plant powder was subjected to successive extractions using different solvents: hexane (F1), dichloromethane (F2), methanol (F3), a 50:50 mixture of methanol and water (F4), and water (F5). Additionally, a parallel extraction was conducted using a 50:50 mixture of methanol and chloroform (F6). All the fractions were evaluated for their antimicrobial activity, and the F6 fraction was characterized using untargeted metabolomics using SPME-GC×GC-TOFMS. The extracts of A. arvensis F3, F4, and F5 showed antibacterial activity against Staphylococcus aureus ATCC 25923 (5 mg/mL), MRSA BA22038 (5 mg/mL), and Pseudomonas aeruginosa ATCC 27853 (10 mg/mL), and fraction F6 showed antibacterial activity against Staphylococcus aureus ATCC 29213 (2 mg/mL), Escherichia coli ATCC 25922 (20 mg/mL), Pseudomonas aeruginosa ATCC 27853 (10 mg/mL), Enterococcus faecalis ATCC 29212 (10 mg/mL), Staphylococcus aureus 024 (2 mg/mL), and Staphylococcus aureus 003 (2 mg/mL). Metabolomic analysis of F6 revealed 2861 peaks with 58 identified compounds through SPME and 3654 peaks with 29 identified compounds through derivatization. The compounds included methyl ester fatty acids, ethyl ester fatty acids, terpenes, ketones, sugars, amino acids, and fatty acids. This study represents the first exploration of A. arvensis metabolomics and its antimicrobial potential, providing valuable insights for plant classification, phytochemical research, and drug discovery.

Evaluation of fresh, frozen, and lyophilized fecal samples by SPME and derivatization methods using GC×GC-TOFMS.

INTRODUCTION: Feces is a highly complex matrix containing thousands of metabolites. It also contains live bacteria and enzymes, and does not have a static chemistry. Consequently, proper control of pre-analytical parameters is critical to minimize unwanted variations in the samples. However, no consensus currently exists on how fecal samples should be stored/processed prior to analysis. OBJECTIVE: The effects of sample handling conditions on fecal metabolite profiles and abundances were examined using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS). METHODS: Solid-phase microextraction (SPME) and derivatization via trimethylsilylation (TMS) were employed as complementary techniques to evaluate fresh, frozen, and lyophilized fecal samples with expanded coverage of the fecal metabolome. The total number of detected peaks and the signal intensities were compared among the different handling conditions. RESULTS: Our analysis revealed that the metabolic profiles of fecal samples depend greatly on sample handling and processing conditions, which had a more pronounced effect on results obtained by SPME than by TMS derivatization. Overall, lyophilization resulted in a greater amount of total and class-specific metabolites, which may be attributed to cell lysis and/or membrane disintegration. CONCLUSIONS: A comprehensive comparison of the sample handling conditions provides a deeper understanding of the physicochemical changes that occur within the samples during freezing and lyophilization. Based on our results, snap-freezing at -80 °C would be preferred over lyophilization for handling samples in the field of fecal metabolomics as this imparts the least change from the fresh condition.

Screening organic contaminants in soil by two-dimensional gas chromatography high-resolution time-of-flight mass spectrometry: A non-target analysis strategy and contaminated area case study.

Thousands of organic substances that are used in industrial applications ultimately enter the soil and may negatively affect human health. Limited numbers of target pollutants are usually monitored in environmental media because of analytical limitations. In this study, a non-target screening method for quickly analyzing multiple soil samples from a contaminated area (a chemical industry park) by two-dimensional gas chromatography high-resolution time-of-flight mass spectrometry was developed. The types of compounds present in the soil samples were preliminarily analyzed through data simplification and visual assessment. A total of 81 organic compounds with detection frequencies ≥40% in the samples from the chemical industry park were selected for identification, including 38 PAHs, 26 oxygenated organic compounds, eight N-containing compounds, and nine other compounds. Potential sources of the organic compounds in the industrial park were investigated. Some pharmaceutical and organic synthetic intermediates in the soil were affected by nearby chemical plants. After assessing the relative abundances and detection frequencies, 36 pollutants that may pose potential risks to the environment were preliminarily identified. The results of the study were helpful for assessing environmental risks around Yangkou industrial park and they will be helpful when assessing risks in other contaminated areas.

Volatile Analysis of Wuliangye Baijiu by LiChrolut EN SPE Fractionation Coupled with Comprehensive GC×GC-TOFMS.

Wuliangye baijiu is one of the most famous Chinese liquors with a protected geographical indication. This study used LiChrolut® EN-based solid-phase extraction (SPE) and fractionation combined with comprehensive two-dimensional chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS) to unveil its volatile composition. The volatiles were isolated with LiChrolut® EN-based SPE and traditional liquid-liquid extraction (LLE). The neutral/basic fractions from LLE and the SPE were fractionated on a LiChrolut® EN SPE column and analyzed by comprehensive GC×GC-TOFMS. Compared with LLE, more esters and alcohols were detected in the SPE-based extraction. The SPE fractionation and GC×GC-TOFMS analysis resulted in the identification of about 500 volatile compounds in more than 3000 peaks of the Wuliangye baijiu. The approach simplifies the complex baijiu composition into functional group-based fractions for reliable identification and analysis. This study provided a confidence volatile identification approach for Chinese baijiu based on the SPE fractionation GC×GC-TOFMS.

M. tuberculosis curli pili (MTP) is associated with alterations in carbon, fatty acid and amino acid metabolism in a THP-1 macrophage infection model.

The initial host-pathogen interaction is crucial for the establishment of infection. An improved understanding of the pathophysiology of Mycobacterium tuberculosis (M. tuberculosis) during macrophage infection can aid the development of intervention therapeutics against tuberculosis. M. tuberculosis curli pili (MTP) is a surface located adhesin, involved in the first point-of-contact between pathogen and host. This study aimed to better understand the role of MTP in modulating the intertwined metabolic pathways of M. tuberculosis and its THP-1 macrophage host. Metabolites were extracted from pelleted wet cell mass of THP-1 macrophages infected with M. tuberculosis wild-type V9124 (WT), Δmtp-deletion mutant and the mtp-complemented strains, respectively, via a whole metabolome extraction method using a 1:3:1 ratio of chloroform:methanol:water. Metabolites were detected by two-dimensional gas chromatography time-of-flight mass spectrometry. Significant metabolites were determined through univariate and multivariate statistical tests and online pathway databases. Relative to the WT, a total of nine and ten metabolites were significantly different in the Δmtp and complement strains, respectively. All nine significant metabolites were found in elevated levels in the Δmtp relative to the WT. Additionally, of the ten significant metabolites, eight were detected in lower levels and two were detected in higher levels in the complement relative to the WT. The absence of the MTP adhesin resulted in reduced virulence of M. tuberculosis leading to alterations in metabolites involved in carbon, fatty acid and amino acid metabolism during macrophage infection, suggesting that MTP plays an important role in the modulation of host metabolic activity. These findings support the prominent role of the MTP adhesin as a virulence factor as well as a promising biomarker for possible diagnostic and therapeutic intervention.

Optimization and Validation of a Headspace Solid-Phase Microextraction with Comprehensive Two-Dimensional Gas Chromatography Time-of-Flight Mass Spectrometric Detection for Quantification of Trace Aroma Compounds in Chinese Liquor (Baijiu).

The detection of trace aroma compounds in samples with complex matrices such as Chinese liquor (Baijiu) requires a combination of several methods, which makes the analysis process very complicated. Therefore, a headspace solid-phase microextraction (HS-SPME) method coupled with two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) was developed for the quantitation of a large number of trace compounds in Baijiu. Optimization of extraction conditions via a series of experiments revealed that dilution of the alcohol content of 8 mL of Baijiu to 5%, followed by the addition of 3.0 g of NaCl and subsequent SPME extraction with DVB/CAR/PDMS fiber coating over 45 min at 45 °C was the most suitable. To check the matrix effects, various model Baijiu matrices were investigated in detail. The quantitative method was established through an optimized model synthetic solution, which can identify 119 aroma compounds (esters, alcohols, fatty acids, aldehydes and ketones, furans, pyrazines, sulfur compounds, phenols, terpenes, and lactones) in the Baijiu sample. The developed procedure provided high recovery (86.79-117.94%), good repeatability (relative standard deviation < 9.93%), high linearity (R2 > 0.99), and lower detection limits than reported methods. The method was successfully applied to study the composition of volatile compounds in different types of Baijiu. This research indicated that the optimized HS-SPME-GC×GC-TOFMS method was a valid and accurate procedure for the simultaneous determination of different types of trace compounds in Baijiu. This developed method will allow an improved analysis of other samples with complex matrices.

Characterization of Aroma Compounds in Cooked Sorghum Using Comprehensive Two-Dimensional Gas Chromatography-Time-of-Flight Mass Spectrometry and Gas Chromatography-Olfactometry-Mass Spectrometry.

Sorghum is the major raw material for the production of Chinese Baijiu (Chinese liquor) and has a great effect on the flavor of Baijiu. Volatiles in cooked glutinous and non-glutinous sorghum samples were extracted using solid-phase microextraction (SPME) and analyzed via comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS) and gas chromatography-olfactometry/mass spectrometry (GC-O/MS). A total of 145 volatile compounds and 52 potent odorant compounds were identified from both sorghum types according to the retention index, MS, aroma, and standards. Based on their aroma features, the compounds were grouped into eight general categories, and the intensities of each aroma group were summed. Moreover, most of the compounds detected in the cooked sorghums were also detected in commercial Chinese Baijiu, indicating that the aroma compounds produced during the sorghum cooking process have a direct and significant influence on the final flavor quality of Baijiu.

Chemical profiling of the human skin surface for malaria vector control via a non-invasive sorptive sampler with GC×GC-TOFMS.

Volatile organic compounds (VOCs) and semi-VOCs detected on the human skin surface are of great interest to researchers in the fields of metabolomics, diagnostics, and skin microbiota and in the study of anthropophilic vector mosquitoes. Mosquitoes use chemical cues to find their host, and humans can be ranked for attractiveness to mosquitoes based on their skin chemical profile. Additionally, mosquitoes show a preference to bite certain regions on the human host. In this study, the chemical differences in the skin surface profiles of 20 human volunteers were compared based on inter-human attractiveness to mosquitoes, as well as inter- and intra-human mosquito biting site preference. A passive, non-invasive approach was followed to sample the wrist and ankle skin surface region. An in-house developed polydimethylsiloxane (PDMS) passive sampler was used to concentrate skin VOCs and semi-VOCs prior to thermal desorption directly in the GC inlet with comprehensive gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS). Compounds from a broad range of chemical classes were detected and identified as contributing to the differences in the surface skin chemical profiles. 5-Ethyl-1,2,3,4-tetrahydronaphthalene, 1,1'-oxybisoctane, 2-(dodecyloxy)ethanol, α,α-dimethylbenzene methanol, methyl salicylate, 2,6,10,14-tetramethylhexadecane, 1,2-benzenedicarboxylic acid, bis(2-methylpropyl) ester, 4-methylbenzaldehyde, 2,6-diisopropylnaphthalene, n-hexadecanoic acid, and γ-oxobenzenebutanoic acid ethyl ester were closely associated with individuals who perceived themselves as attractive for mosquitoes. Additionally, biological lead compounds as potential attractants or repellants in vector control strategies were tentatively identified. Results augment current knowledge on human skin chemical profiles and show the potential of using a non-invasive sampling approach to investigate anthropophilic mosquito-host interactions. Graphical abstract.

Comprehensive chemical characterization of the aerosol generated by a heated tobacco product by untargeted screening.

A suite of untargeted methods has been applied for the characterization of aerosol from the Tobacco Heating System 2.2 (THS2.2), a heated tobacco product developed by Philip Morris Products S.A. and commercialized under the brand name IQOS®. A total of 529 chemical constituents, excluding water, glycerin, and nicotine, were present in the mainstream aerosol of THS2.2, generated by following the Health Canada intense smoking regimen, at concentrations ≥ 100 ng/item. The majority were present in the particulate phase (n = 402), representing more than 80% of the total mass determined by untargeted screening; a proportion were present in both particulate and gas-vapor phases (39 compounds). The identities for 80% of all chemical constituents (representing > 96% of the total determined mass) were confirmed by the use of authentic analytical reference materials. Despite the uncertainties that are recognized to be associated with aerosol-based untargeted approaches, the reported data remain indicative that the uncharacterized fraction of TPM generated by THS2.2 has been evaluated to the fullest practicable extent. To the best of our knowledge, this work represents the most comprehensive chemical characterization of a heated tobacco aerosol to date. Graphical abstract.

Three Extraction Methods in Combination with GC×GC-TOFMS for the Detailed Investigation of Volatiles in Chinese Herbaceous Aroma-Type Baijiu.

In this study, the detailed volatile compositions of Chinese herbaceous aroma-type Baijiu (HAB) were characterized by comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-TOFMS). A total of 606 compounds were tentatively identified by similarity, mass spectral data, and retention indices, among which 247 compounds were positively verified by authentic standards. Esters were present in higher numbers (179), followed by aldehydes and ketones (111), and alcohols (81). In addition, there were also many terpenes (82), sulfides (37), furans (29), nitrogenous compounds (29), lactones (17), and so on. Meanwhile, the extraction effects of volatile components from different sample pretreatment methods (headspace solid-phase microextraction (HS-SPME), solid phase extraction (SPE), and stir bar sorptive extraction (SBSE)) for HAB were also revealed. The results indicated that HS-SPME has a better extraction effect on easily volatile compounds, such as alcohols and sulfides, especially for terpenes. SPE was particularly beneficial for the analysis of nitrogen-containing compounds; SBSE showed medium extraction ability for most types of compounds and was more suitable for the target analysis of trace content substances.

Discrimination and Identification of Aroma Profiles and Characterized Odorants in Citrus Blend Black Tea with Different Citrus Species.

Citrus blend black teas are popular worldwide, due to its unique flavor and remarkable health benefits. However, the aroma characteristics, aroma profiles and key odorants of it remain to be distinguished and cognized. In this study, the aroma profiles of 12 representative samples with three different cultivars including citrus (Citrus reticulata), bergamot (Citrus bergamia), and lemon (Citrus limon) were determined by a novel approach combined head space-solid phase microextraction (HS-SPME) with comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS). A total of 348 volatile compounds, among which comprised esters (60), alkenes (55), aldehydes (45), ketones (45), alcohols (37), aromatic hydrocarbons (20), and some others were ultimately identified. The further partial least squares discrimination analysis (PLS-DA) certified obvious differences existed among the three groups with a screening result of 30 significant differential key volatile compounds. A total of 61 aroma-active compounds that mostly presented green, fresh, fruity, and sweet odors were determined in three groups with gas chromatography-olfactometry/mass spectrometry (GC-O/MS) assisted analysis. Heptanal, limonene, linalool, and trans-ß-ionone were considered the fundamental odorants associated with the flavors of these teas. Comprehensive analysis showed that limonene, ethyl octanoate, copaene, ethyl butyrate (citrus), benzyl acetate, nerol (bergamot) and furfural (lemon) were determined as the characterized odorants for each type.

Optimization and Characterization of Microwave-Assisted Hydro-Distillation Extraction of Essential Oils from Cinnamomum camphora Leaf and Recovery of Polyphenols from Extract Fluid.

In this study, the efficiency of microwave-assisted hydro-distillation (MAHD) to extract essential oil from Cinnamomum camphora leaf, and the recovery of polyphenols from extract fluid were investigated. The effects of microwave power, liquid-to-material ratio, and extraction time on the extraction efficiency were studied by a single factor test as well as the response surface methodology (RSM) based on the central composite design method. The optimal extraction conditions were a microwave power of 786.27 W, liquid-to-material ratio of 7.47:1 mL/g, and extraction time of 35.57 min. The yield of essential oil was 3.26 ± 0.05% (w/w), and the recovery of polyphenols was 4.97 ± 0.02 mg gallic acid equivalent/g dry weight under the optimal conditions. Furthermore, the comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS) was used to characterize the essential oils of fresh and fallen leaves, and 159 individual compounds were tentatively identified, accounting for more than 89.68 and 87.88% of the total contents, respectively. The main ingredients include sabinene, l-ß-pinene, ß-myrcene, α-terpineol, 3-heptanone, and ß-thujene, as well as δ-terpineol and 3-heptanone, which were first identified in C. camphora essential oil. In conclusion, the MAHD method could extract essential oil from C. camphora with high efficiency, and the polyphenols could be obtained from the extract fluid at the same time, improving the utilization of C. camphora leaf.

Volatile Compounds of Selected Raw and Cooked Brassica Vegetables.

Brassica vegetables are a significant component of the human diet and their popularity is systematically increasing. The interest in plants from this group is growing because of numerous reports focused on their pro-health properties. However, some consumers are not enthusiastic about these vegetables because of their specific bitter taste and sharp, sulfurous aroma. In this study, the volatile composition of 15 Brassica cultivars (five Brussels sprouts, four kohlrabi, three cauliflower and three broccoli), both raw and cooked, was analyzed by solid phase microextraction and comprehensive two-dimensional gas chromatography with time of flight mass spectrometry (SPME-GC×GC-ToFMS). Differences were found between the analyzed vegetables, as well as different cultivars of the same vegetable. Moreover, the influence of cooking on the composition of volatile compounds was evaluated. All the vegetables were frozen before analyses, which is why the impact of this process on the volatile organic compounds (VOCs) was included. The most abundant groups of compounds were sulfur components (including bioactive isothiocyanates), nitriles, aldehydes and alcohols. Cooking in general caused a decrease in the abundance of main volatiles. However, the amount of bioactive isothiocyanates increased in most cultivars after cooking. The effect of freezing on the volatile fraction was presented based on the Brussels sprout cultivars. Most of the changes were closely related to the activity of the lipoxygenase (LOX) pathway enzymes. These are characterized by a marked reduction in alcohol contents and an increment in aldehyde contents. Moreover, important changes were noted in the concentrations of bioactive components, e.g., isothiocyanates. This research included a large set of samples consisting of many cultivars of each analyzed vegetable, which is why it provides a considerable body of general information concerning volatiles in Brassica vegetables.

Analysis of Volatile Compounds in Pears by HS-SPME-GC×GC-TOFMS.

Aroma plays an important role in fruit quality and varies among different fruit cultivars. In this study, a sensitive and accurate method based on headspace solid-phase microextraction (HS-SPME) coupled with comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) was developed to comprehensively compare aroma components of five pear cultivars. In total, 241 volatile compounds were identified and the predominant volatile compounds were esters (101 compounds), followed by alcohols (20 compounds) and aldehydes (28 compounds). The longyuanyangli has the highest relative concentration (838.12 ng/g), while the Packham has the lowest (208.45 ng/g). This study provides a practical method for pear aroma analysis using SPME and GC×GC-TOFMS.

Profiling the scent of weathered training aids for blood-detection dogs.

At outdoor crime scenes, cadaver-detection and blood-detection dogs may be tasked with locating blood that is days, weeks or months old. Although it is known that the odour profile of blood will change during this time, it is currently unknown how the profile changes when exposed to the environment. Such variables must be studied in order to understand when the odour profile is no longer detectable by the scent-detection dogs and other crime scene tools should be implemented. In this study, blood was deposited onto concrete and varnished wood surfaces and weathered in an outdoor environment over a three-month period. Headspace samples were collected using solid phase microextraction (SPME) and analysed using comprehensive two-dimensional gas chromatography - time-of-flight mass spectrometry (GC×GC-TOFMS). The chemical odour profiles were compared with the behavioural responses of cadaver-detection and blood-detection dogs during training. Data interpretation using principal component analysis (PCA) and hierarchical cluster analysis (HCA) established that the blood odour could no longer be detected using SPME-GC×GC-TOFMS after two months of weathering on both surfaces. Conversely, the blood-detection dogs had difficulty locating the blood samples after one month of weathering on concrete and after one week of weathering on varnished wood. The scent-detection dogs evaluated herein had not been previously exposed to environmentally weathered blood samples during training. Given that this study was conducted to test the dogs' baseline abilities, it is expected that with repeated exposure, the dogs' capabilities would likely improve. The knowledge gained from this study can assist in providing law enforcement with more accurate training aids for blood-detection dogs and can improve their efficiency when deployed to outdoor crime scenes.

Comprehensive two-dimensional gas chromatographic profiling and chemometric interpretation of the volatile profiles of sweat in knit fabrics.

Human axillary sweat is a poorly explored biofluid within the context of metabolomics when compared to other fluids such as blood and urine. In this paper, we explore the volatile organic compounds emitted from two different types of fabric samples (cotton and polyester) which had been worn repeatedly during exercise by participants. Headspace solid-phase microextraction (SPME) and comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) were employed to profile the (semi)volatile compounds on the fabric. Principal component analysis models were applied to the data to aid in visualizing differences between types of fabrics, wash treatment, and the gender of the subject who had worn the fabric. Statistical tools included with commercial chromatography software (ChromaTOF) and a simple Fisher ratio threshold-based feature selection for model optimization are compared with a custom-written algorithm that uses cluster resolution as an objective function to maximize in a hybrid backward-elimination forward-selection approach for optimizing the chemometric models in an effort to identify some compounds that correlate to differences between fabric types. The custom algorithm is shown to generate better models than the simple Fisher ratio approach. Graphical Abstract A route from samples and questions to data and then answers.