Elucidation of Biochemical Pathways Underlying VOCs Production in A549 Cells

Precision detection of select human lung cancer biomarkers and cell lines using honeybee olfactory neural circuitry as a novel gas sensor

Human breath contains biomarkers (odorants) that can be targeted for early disease detection. It is well known that honeybees have a keen sense of smell and can detect a wide variety of odors at low concentrations. Here, we employ honeybee olfactory neuronal circuitry to classify human lung cancer volatile biomarkers at different concentrations and their mixtures at concentration ranges relevant to biomarkers in human breath from parts-per-billion to parts-per-trillion. We also validated this brain-based sensing technology by detecting human non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) cell lines using the 'smell' of the cell cultures. Different lung cancer biomarkers evoked distinct spiking response dynamics in the honeybee antennal lobe neurons indicating that those neurons encoded biomarker-specific information. By investigating lung cancer biomarker-evoked population neuronal responses from the honeybee antennal lobe, we classified individual human lung cancer biomarkers successfully (88% success rate). When we mixed six lung cancer biomarkers at different concentrations to create 'synthetic lung cancer' vs. 'synthetic healthy' human breath, honeybee population neuronal responses were able to classify those complex breath mixtures reliably with exceedingly high accuracy (93-100% success rate with a leave-one-trial-out classification method). Finally, we employed this sensor to detect human NSCLC and SCLC cell lines and we demonstrated that honeybee brain olfactory neurons could distinguish between lung cancer vs. healthy cell lines and could differentiate between different NSCLC and SCLC cell lines successfully (82% classification success rate). These results indicate that the honeybee olfactory system can be used as a sensitive biological gas sensor to detect human lung cancer.

Hypoxia and lactate influence VOC production in A549 lung cancer cells

Introduction: Cancer cells emit characteristic volatile organic compounds (VOCs), which are potentially generated from ROS-based lipid peroxidation of polyunsaturated fatty acids. The metabolism of such VOCs and their regulation remain to be fully investigated. In fact, the enzymes involved in the synthesis of these VOCs have not been described yet. Methods: In this study, we firstly conducted in vitro enzyme assays and demonstrated that recombinant alcohol dehydrogenase (ADH) converted Trans 2-hexenal into Trans 2-hexenol. The latter has previously been reported as a cancer VOC. To study VOC metabolism, 14 different culture conditions were compared in view of Trans 2-hexenol production. Results and discussion: The data indicate that hypoxia and the addition of lactate positively influenced Trans 2-hexenol production in A549 cancer cells. The RNAseq data suggested certain gene expressions in the VOC pathway and in lactate signaling, parallel to VOC production. This implies that hypoxia and lactate signaling with a VOC production can be characteristic for cancer in vitro.

Changes in lung epithelial cell volatile metabolite profile induced by pro-fibrotic stimulation with TGF-β1

Volatile organic compounds (VOCs) have shown promise as potential biomarkers in idiopathic pulmonary fibrosis. Measuring VOCs in the headspace ofin vitromodels of lung fibrosis may offer a method of determining the origin of those detected in exhaled breath. The aim of this study was to determine the VOCs associated with two lung cell lines (A549 and MRC-5 cells) and changes associated with stimulation of cells with the pro-fibrotic cytokine, transforming growth factor (TGF)-β1. A dynamic headspace sampling method was used to sample the headspace of A549 cells and MRC-5 cells. These were compared to media control samples and to each other to identify VOCs which discriminated between cell lines. Cells were then stimulated with the TGF-β1 and samples were compared between stimulated and unstimulated cells. Samples were analysed using thermal desorption-gas chromatography-mass spectrometry and supervised analysis was performed using sparse partial least squares-discriminant analysis (sPLS-DA). Supervised analysis revealed differential VOC profiles unique to each of the cell lines and from the media control samples. Significant changes in VOC profiles were induced by stimulation of cell lines with TGF-β1. In particular, several terpenoids (isopinocarveol, sativene and 3-carene) were increased in stimulated cells compared to unstimulated cells. VOC profiles differ between lung cell lines and alter in response to pro-fibrotic stimulation. Increased abundance of terpenoids in the headspace of stimulated cells may reflect TGF-β1 cell signalling activity and metabolic reprogramming. This may offer a potential biomarker target in exhaled breath in IPF.

Antihyperlipidemic effect of Vaccinium dunalianum buds based on biological activity screening and LC-MS

ETHNOPHARMACOLOGICAL RELEVANCE

The buds of Vaccinium dunalianum Wight are used as folk medicine in the Yi settlement of the Yunnan Province, China. It has long been used as herbal tea in the local area owing to its effects of lowering blood lipids and body weight. However, there are only a few studies on its antihyperlipidemic effects, effective substances and mechanisms, especially its effectiveness in diet-induced hyperlipidemia.

AIM OF THE STUDY

This study aimed to elucidate the therapeutic effects, pharmacodynamic material bases, and mechanisms of V. dunalianum buds on diet-induced hyperlipidemia.

MATERIALS AND METHODS

A high-fat diet-induced hyperlipidemic Sprague-Dawley (SD) rat model was established. Rats were gavaged with different doses of aqueous extract of V. dunalianum(VDW) for 8 weeks and their sera and organ samples were collected. The antihyperlipidemic effect of VDW on SD rats was evaluated based on the biochemical indices and histopathological outcomes. Liquid chromatography-mass spectrometry(LC-MS) was used to determine the main components in VDW, which were separated and purified using sequential chromatographic methods. Their chemical structures were determined using high-resolution electrospray ionization mass spectroscopy and nuclear magnetic resonance spectroscopy. 6'-O-caffeoyl-arbutin, as the principal component of VDW, was also evaluated for its antihyperlipidemic activity using an approach similar to that used for VDW. Lastly, the potential targets of VDW and 6'-O-caffeoyl-arbutin in lowering blood lipids were screened out using network pharmacology, and the selected targets were docked with arbutin derivatives. The expression of target proteins was determined using western blotting to illustrate the antihyperlipidemic mechanisms of VDW and 6'-O-caffeoyl-arbutin.

RESULTS

VDW reduced triglyceride, total cholesterol, low-density lipoprotein, alanine transaminase, and aspartate transaminase levels in the serum of modeled rats, and increased high-density lipoprotein levels. There was an improvement in steatoses, and lipid droplet accumulation decreased in vivo after VDW intervention. LC-MS revealed that VDW mainly contained arbutin and chlorogenic acid derivatives. Sixteen compounds were isolated and identified. 6'-O-caffeoyl-arbutin was the main compound of VDW (>21.67%) that showed obvious antihyperlipidemic effect with low hepatic damage at different doses. PTGS2, ADH1C, and MAOB were screened out using network pharmacology and they showed strong correlations with arbutin derivative through molecular docking. Results from WB showed that VDW and 6'-O-caffeoyl-arbutin could reduce blood lipid levels by reducing the protein expression of PTGS2, ADH1C, and MAOB.

CONCLUSIONS

6'-O-caffeoyl-arbutin was the main component of V. dunalianum buds. VDW and 6'-O-caffeoyl-arbutin could regulate blood lipid levels in the high-fat diet-induced rat model of hyperlipidemia without damaging their vital organs. Furthermore, they could regulate the expression of PTGS2, ADH1C, and MAOB proteins and play a role in lowering blood lipids. The findings of this study lay a foundation for the further development of V. dunalianum and 6'-O-caffeoyl-arbutin as health supplements or drugs for the management of hyperlipidemia.

Validation of volatile metabolites of pulmonary oxidative injury: a bench to bedside study

Background

Changes in exhaled volatile organic compounds (VOCs) can be used to discriminate between respiratory diseases, and increased concentrations of hydrocarbons are commonly linked to oxidative stress. However, the VOCs identified are inconsistent between studies, and translational studies are lacking.

Methods

In this bench to bedside study, we captured VOCs in the headspace of A549 epithelial cells after exposure to hydrogen peroxide (H₂O₂), to induce oxidative stress, using high-capacity polydimethylsiloxane sorbent fibres. Exposed and unexposed cells were compared using targeted and untargeted analysis. Breath samples of invasively ventilated intensive care unit patients (n=489) were collected on sorbent tubes and associated with the inspiratory oxygen fraction (F _IO2 ) to reflect pulmonary oxidative stress. Headspace samples and breath samples were analysed using gas chromatography and mass spectrometry.

Results

In the cell, headspace octane concentration was decreased after oxidative stress (p=0.0013), while the other VOCs were not affected. 2-ethyl-1-hexanol showed an increased concentration in the headspace of cells undergoing oxidative stress in untargeted analysis (p=0.00014). None of the VOCs that were linked to oxidative stress showed a significant correlation with F _IO2 (R_s range: -0.015 to -0.065) or discriminated between patients with F _IO2 ≥0.6 or below (area under the curve range: 0.48 to 0.55).

Conclusion

Despite a comprehensive translational approach, validation of known and novel volatile biomarkers of oxidative stress was not possible in patients at risk of pulmonary oxidative injury. The inconsistencies observed highlight the difficulties faced in VOC biomarker validation, and that caution is warranted in the interpretation of the pathophysiological origin of discovered exhaled breath biomarkers.

The Versatility and Diagnostic Potential of VOC Profiling for Noninfectious Diseases

A variety of volatile organic compounds (VOCs) are produced and emitted by the human body every day. The identity and concentration of these VOCs reflect an individual's metabolic condition. Information regarding the production and origin of VOCs, however, has yet to be congruent among the scientific community. This review article focuses on the recent investigations of the source and detection of biological VOCs as a potential for noninvasive discrimination between healthy and diseased individuals. Analyzing the changes in the components of VOC profiles could provide information regarding the molecular mechanisms behind disease as well as presenting new approaches for personalized screening and diagnosis. VOC research has prioritized the study of cancer, resulting in many research articles and reviews being written on the topic. This review summarizes the information gained about VOC cancer studies over the past 10 years and looks at how this knowledge correlates with and can be expanded to new and upcoming fields of VOC research, including neurodegenerative and other noninfectious diseases. Recent advances in analytical techniques have allowed for the analysis of VOCs measured in breath, urine, blood, feces, and skin. New diagnostic approaches founded on sensor-based techniques allow for cheaper and quicker results, and we compare their diagnostic dependability with gas chromatography- and mass spectrometry-based techniques. The future of VOC analysis as a clinical practice and the challenges associated with this transition are also discussed and future research priorities are summarized.

Harnessing insect olfactory neural circuits for detecting and discriminating human cancers

There is overwhelming evidence that presence of cancer alters cellular metabolic processes, and these changes are manifested in emitted volatile organic compound (VOC) compositions of cancer cells. Here, we take a novel forward engineering approach by developing an insect olfactory neural circuit-based VOC sensor for cancer detection. We obtained oral cancer cell culture VOC-evoked extracellular neural responses from in vivo insect (locust) antennal lobe neurons. We employed biological neural computations of the antennal lobe circuitry for generating spatiotemporal neuronal response templates corresponding to each cell culture VOC mixture, and employed these neuronal templates to distinguish oral cancer cell lines (SAS, Ca9-22, and HSC-3) vs. a non-cancer cell line (HaCaT). Our results demonstrate that three different human oral cancers can be robustly distinguished from each other and from a non-cancer oral cell line. By using high-dimensional population neuronal response analysis and leave-one-trial-out methodology, our approach yielded high classification success for each cell line tested. Our analyses achieved 76-100% success in identifying cell lines by using the population neural response (n = 194) collected for the entire duration of the cell culture study. We also demonstrate this cancer detection technique can distinguish between different types of oral cancers and non-cancer at different time-matched points of growth. This brain-based cancer detection approach is fast as it can differentiate between VOC mixtures within 250 ms of stimulus onset. Our brain-based cancer detection system comprises a novel VOC sensing methodology that incorporates entire biological chemosensory arrays, biological signal transduction, and neuronal computations in a form of a forward-engineered technology for cancer VOC detection.

From the First to Third Generation of Neonicotinoids: Implication for Saving the Loss of Fruit Quality and Flavor by Pesticide Applications

Neonicotinoids can control crop pests with high efficiency and low cost and have quickly swept one-fourth of the global insecticide market since the launch of imidacloprid in 1991. Imidacloprid and acetamiprid, the first generation of neonicotinoids, and dinotefuran, the representative of third generation of neonicotinoids, were applied on tomato plants individually to investigate neonicotinoid effects on tomato fruit quality, especially on appearance parameters, sugar, acid, and aroma compounds. Compared with the control, fewer differences in the transcriptome profile, sugar, acid, and volatile organic compound (VOC) contents, and sensory analysis results were shown in dinotefuran treatments than in the other two treatments. Therefore, dinotefuran was more recommended to control pests of tomatoes with less loss of fruit flavor and quality as well as lower ecological risks.

Dissecting the ferroptosis-related prognostic biomarker and immune microenvironment of driver gene-negative lung cancer

Despite significant advances in targeted and immune therapy for non-small cell lung cancer (NSCLC), effective therapies for wild-type epidermal growth factor receptor/anaplastic lymphoma kinase (EGFR/ALK^WT) with low expression of programmed death ligand-1 (PD-L1) NSCLC remain elusive. Numerous studies have shown that ferroptosis plays an essential role in antitumor activity. To identify the molecular regulation patterns associated with ferroptosis, 351 EGFR/ALK^WT NSCLC samples with low-level PD-L1 were extracted from The Cancer Genome Atlas (TCGA) and clustered using the k-means clustering technique. The two clusters associated with ferroptosis showed significantly different prognoses. In total, 169 differential expression genes (DEGs) were identified. Cluster differential analysis revealed that Cluster 1 had a significantly poorer overall survival (OS) and was associated with more negative immune regulation. In addition, TCGA samples were randomly assigned in a 7:3 ratio to a training group or testing group. A signature of eight genes associated with ferroptosis was established in the training cohort using DEGs and validated in the test cohort and three independent cohorts (GSE72049, GSE41271, and GSE50081). The 5-year area under the curve (AUC) was 0.713, which was significantly higher than that of other predictors, including TNM stage and age. Furthermore, the risk score was associated with immune function, immune infiltration, and immunotherapy response, with high-risk patients having a worse prognosis, an immune-suppressing phenotype, and a poor response to immune checkpoint inhibitors. This study aims to contribute to our understanding of the biological role of ferroptosis in EGFR/ALK^WT NSCLC with low-level PD-L1, laying the groundwork for the development of novel therapeutic strategies.

Longitudinal two-dimensional gas chromatography mass spectrometry as a non-destructive at-line monitoring tool during cell manufacturing identifies volatile features correlative to cell product quality

BACKGROUND AIMS

Cell therapies have emerged as a potentially transformative therapeutic modality in many chronic and incurable diseases. However, inherent donor and patient variabilities, complex manufacturing processes, lack of well-defined critical quality attributes and unavailability of in-line or at-line process or product analytical technologies result in significant variance in cell product quality and clinical trial outcomes. New approaches for overcoming these challenges are needed to realize the potential of cell therapies.

METHODS

Here the authors developed an untargeted two-dimensional gas chromatography mass spectrometry (GC×GC-MS)-based method for non-destructive longitudinal at-line monitoring of cells during manufacturing to discover correlative volatile biomarkers of cell proliferation and end product potency.

RESULTS

Specifically, using mesenchymal stromal cell cultures as a model, the authors demonstrated that GC×GC-MS of the culture medium headspace can effectively discriminate between media types and tissue sources. Headspace GC×GC-MS identified specific volatile compounds that showed a strong correlation with cell expansion and product functionality quantified by indoleamine-2,3-dioxygenase and T-cell proliferation/suppression assays. Additionally, the authors discovered increases in specific volatile metabolites when cells were treated with inflammatory stimulation.

CONCLUSIONS

This work establishes GC×GC-MS as an at-line process analytical technology for cell manufacturing that could improve culture robustness and may be used to non-destructively monitor culture state and correlate with end product function.

Volatilomic Signatures of AGS and SNU-1 Gastric Cancer Cell Lines

In vitro studies can help reveal the biochemical pathways underlying the origin of volatile indicators of numerous diseases. The key objective of this study is to identify the potential biomarkers of gastric cancer. For this purpose, the volatilomic signatures of two human gastric cancer cell lines, AGS (human gastric adenocarcinoma) and SNU-1 (human gastric carcinoma), and one normal gastric mucosa cell line (GES-1) were investigated. More specifically, gas chromatography mass spectrometry has been applied to pinpoint changes in cell metabolism triggered by cancer. In total, ten volatiles were found to be metabolized, and thirty-five were produced by cells under study. The volatiles consumed were mainly six aldehydes and two heterocyclics, whereas the volatiles released embraced twelve ketones, eight alcohols, six hydrocarbons, three esters, three ethers, and three aromatic compounds. The SNU-1 cell line was found to have significantly altered metabolism in comparison to normal GES-1 cells. This was manifested by the decreased production of alcohols and ketones and the upregulated emission of esters. The AGS cells exhibited the increased production of methyl ketones containing an odd number of carbons, namely 2-tridecanone, 2-pentadecanone, and 2-heptadecanone. This study provides evidence that the cancer state modifies the volatilome of human cells.

Potent necrosis effect of methanethiol mediated by METTL7B enzyme bioactivation mechanism in 16HBE cell

Methanethiol is a widely existing malodorous pollutant with health effects on the human population. However, the cytotoxicity mechanism of methanethiol in vitro and its metabolic transformation (bioactivation or detoxification) have not been fully elucidated. Herein, the metabolites of methanethiol during cell culture and the cytotoxicity of methanethiol in human bronchial epithelial (16HBE) cells were investigated. Results indicate that methanethiol (10-50 μM) was partially converted into dimethyl sulfide, mainly catalyzed by thiol S-methyltransferase in the 16HBE cells, and then it induced potent cytotoxicity and cell membrane permeability. Moreover, methanethiol induced intracellular reactive oxygen species (ROS) up to 50 μM and further activated the tumor necrosis factor (TNF) signaling pathway, which eventually led to the decline in the mitochondrial membrane potential (MMP) and cell necrosis. However, all these effects were significantly alleviated with gene silencing of the methyltransferase-like protein 7B (METTL7B). These results indicate that methanethiol may induce cell necrosis in human respiratory tract cells mainly mediated by S-methyltransferase with interfering TNF and ROS induction. Non-target metabolomics results suggest that methanethiol potently affects expression of endogenous small molecule metabolites in 16HBE cells. To some extent, this work shows the possible conversion path and potential injury mechanism of human respiratory tract cells exposed to methanethiol.

Application of Thin-Film Microextraction to Analyze Volatile Metabolites in A549 Cancer Cells

Volatile organic compounds (VOCs) have been proposed in the last two decades as biomarkers for disease detection and therapeutic monitoring. Model in vitro experiments with established cell lines are fundamental to clarify whether given VOCs originate from normal human cells or pathogens, including transformed cancer cells. Due to the trace concentrations of target metabolites, adsorptive enrichment is needed before gas chromatography-mass spectrometry (GC-MS) analysis, with solid-phase microextraction (SPME) being perfectly suited for this purpose. Here, a modification of SPME, the thin-film microextraction (TFME) technique, is proposed for analysis of cellular VOCs, which utilizes a planar mesh coated with stationary phase to increase the extraction phase volume and active surface area. In this study, four different adsorbents were compared: carboxen, divinylbenzene, hydrophobic−lipophilic balanced and polydimethylsiloxane. Amongst them, HLB sheets using poly(divinylbenzene-co-N-vinyl-pyrrolidone) skeleton structure proved to be the most versatile, enabling the most sensitive analysis of VOCs with a broad polarity and volatility. For HLB, sampling type (internal static headspace, external bi-directional headspace), extraction temperature and extraction time were also examined. An established method was successfully applied to analyze metabolites produced by A549 cells revealing five volatiles at significantly higher (additionally benzaldehyde at lower) levels in cell culture medium compared to the cell-free reference medium headspace.

In vitro toxic synergistic effects of exogenous pollutants-trimethylamine and its metabolites on human respiratory tract cells

The wide presence of volatile organic amines in atmosphere has been clarified to relate to adverse effects on human respiratory health. However, toxic effects of them on human respiratory tract and their metabiotic mechanism of in vivo transformation have not been elucidated yet. Herein, cell viability and production of reactive oxygen species (ROSs) were first investigated during acute exposure of trimethylamine (TMA) to bronchial epithelial cells (16HBE), along with identification of toxic metabolites and metabolic mechanisms of TMA from headspace atmosphere and cell culture. Results showed that cell activity decreased and ROS production increased with raising exposure TMA concentration. Toxic effects may be induced not only by TMA itself, but also more likely by its cellular metabolites. Increased dimethylamine identified in headspace atmosphere and cell solution was the main metabolite of TMA, and methylamine was also confirmed to be a further metabolite. In addition, TMA can also be oxygenated to generate N,N-dimethylformamide and N,N'-Bis(2-hydroxyethyl)-1,2-ethanediaminium by N-formylation or hydroxylation, which was considered to be the participation of cytochrome P450 (CYP) enzymes. Overall, we can conclude that respiratory tract cells may produce more toxic metabolites during exposure of toxic organic amines, which together further induce cellular oxidative stress and necrosis. Hence, the environment and health impact of metabolites as well as original parent atmospheric organic amines should be paid more attention in further researches and disease risk assessments.

The Genetic Basis of Tomato Aroma

Tomato (Solanum lycopersicum L.) aroma is determined by the interaction of volatile compounds (VOCs) released by the tomato fruits with receptors in the nose, leading to a sensorial impression, such as "sweet", "smoky", or "fruity" aroma. Of the more than 400 VOCs released by tomato fruits, 21 have been reported as main contributors to the perceived tomato aroma. These VOCs can be grouped in five clusters, according to their biosynthetic origins. In the last decades, a vast array of scientific studies has investigated the genetic component of tomato aroma in modern tomato cultivars and their relatives. In this paper we aim to collect, compare, integrate and summarize the available literature on flavour-related QTLs in tomato. Three hundred and 5ifty nine (359) QTLs associated with tomato fruit VOCs were physically mapped on the genome and investigated for the presence of potential candidate genes. This review makes it possible to (i) pinpoint potential donors described in literature for specific traits, (ii) highlight important QTL regions by combining information from different populations, and (iii) pinpoint potential candidate genes. This overview aims to be a valuable resource for researchers aiming to elucidate the genetics underlying tomato flavour and for breeders who aim to improve tomato aroma.

The Volatilomic Footprints of Human HGC-27 and CLS-145 Gastric Cancer Cell Lines

The presence of certain volatile biomarkers in the breath of patients with gastric cancer has been reported by several studies; however, the origin of these compounds remains controversial. In vitro studies, involving gastric cancer cells may address this problem and aid in revealing the biochemical pathways underlying the production and metabolism of gastric cancer volatile indicators. Gas chromatography with mass spectrometric detection, coupled with headspace needle trap extraction as the pre-concentration technique, has been applied to map the volatilomic footprints of human HGC-27 and CLS-145 gastric cancer cell lines and normal Human Stomach Epithelial Cells (HSEC). In total, 27 volatile compounds are found to be associated with metabolism occurring in HGC-27, CLS-145, and HSEC. Amongst these, the headspace concentrations of 12 volatiles were found to be reduced compared to those above just the cultivating medium, namely there was an observed uptake of eight aldehydes (2-methylpropanal, 2-methyl-2-propenal, 2-methylbutanal, 3-methylbutanal, hexanal, heptanal, nonanal, and benzaldehyde), three heterocyclic compounds (2-methyl-furan, 2-ethyl-furan, and 2-pentyl-furan), and one sulfur-containing compound (dimethyl disulphide). For the other 15 volatiles, the headspace concentrations above the healthy and cancerous cells were found to be higher than those found above the cultivating medium, namely the cells were found to release three esters (ethyl acetate, ethyl propanoate, and ethyl 2-methylbutyrate), seven ketones (2-pentanone, 2-heptanone, 2-nonanone, 2-undecanone, 2-tridecanone, 2-pentadecanone, and 2-heptadecanone), three alcohols (2-methyl-1-butanol, 3-methyl-1-butanol, and 2-ethyl-1-hexanol), one aromatic compound (toluene), and one sulfur containing compound [2-methyl-5-(methylthio) furan]. In comparison to HSEC, HGC-27 cancer cell lines were found to have significantly altered metabolism, manifested by an increased production of methyl ketones containing an odd number of carbons. Amongst these species, three volatiles were found exclusively to be produced by this cell line, namely 2-undecanone, 2-tridecanone, and 2-heptadecanone. Another interesting feature of the HGC-27 footprint is the lowered level of alcohols and esters. The CLS-145 cells exhibited less pronounced changes in their volatilomic pattern compared to HSEC. Their footprint was characterized by the upregulated production of esters and 2-ethyl-hexanol and downregulated production of other alcohols. We have therefore demonstrated that it is possible to differentiate between cancerous and healthy gastric cells using biochemical volatile signatures.

Sample Introduction Method in Gas Chromatography

In this review, we summarize the methods of sample introduction into a gas chromatograph. For volatile organic compounds, headspace measurements and purge-trap methods have been used traditionally. Recently, the trapped headspace method has been used in water quality testing. In addition, various solid-state adsorption methods have been developed, including a method in which the adsorbent is placed inside a needle, while new adsorbents and their applications have also been introduced.