Background
Metabolomics aims to identify the changes in endogenous metabolites of biological systems in response to intrinsic and extrinsic factors. This is accomplished through untargeted, ...semi-targeted and targeted based approaches. Untargeted and semi-targeted methods are typically applied in hypothesis-generating investigations (aimed at measuring as many metabolites as possible), while targeted approaches analyze a relatively smaller subset of biochemically important and relevant metabolites. Regardless of approach, it is well recognized amongst the metabolomics community that gas chromatography-mass spectrometry (GC–MS) is one of the most efficient, reproducible and well used analytical platforms for metabolomics research. This is due to the robust, reproducible and selective nature of the technique, as well as the large number of well-established libraries of both commercial and ‘in house’ metabolite databases available.
Aim of review
This review provides an overview of developments in GC–MS based metabolomics applications, with a focus on sample preparation and preservation techniques. A number of chemical derivatization (
in-time, in-liner, offline
and microwave assisted) techniques are also discussed. Electron impact ionization and a summary of alternate mass analyzers are highlighted, along with a number of recently reported new GC columns suited for metabolomics. Lastly, multidimensional GC–MS and its application in environmental and biomedical research is presented, along with the importance of bioinformatics.
Key scientific concepts of review
The purpose of this review is to both highlight and provide an update on GC–MS analytical techniques that are common in metabolomics studies. Specific emphasis is given to the key steps within the GC–MS workflow that those new to this field need to be aware of and the common pitfalls that should be looked out for when starting in this area.
•Skatole, sclareololide and sclareololide were first identified in Laoshan tea.•Co-eluted compounds (furfural, cis-linalool oxide) were separating by GC × GC-qMS.•The interactions exist among aroma ...compounds in tea samples.
To investigate the key aroma compounds in Laoshan green teas (Huangshan (S1), Changling (S2), and Fangling (S3)), gas chromatography-mass spectrometry-olfactometry (GC-MS-O), a flame photometric detector (FPD), odor activity value (OAV), and comprehensive two-dimensional gas chromatography mass spectrometry (GC × GC-qMS) were employed. A total of 50 aroma compounds were perceived and 24 compounds were identified as important compounds related to OAV, such as dimethyl sulfide (OAV: 126–146), skatole (OAV: 27–50), furaneol (OAV: 8–27), (Z)-jasmone (OAV: 16–23), 2-methylbutanal (OAV: 15–22), and 3-methylbutanal (OAV: 68–87). Furthermore, the S-curve method was used to research the effect of aroma compounds on the threshold of aroma recombination (AR). The AR thresholds decreased from 3.8 mL to 0.45, 0.66, 0.93, 0.95, 0.75, 1.09, 3.01, and 2.57 mL after addition of eight compounds (skatole, furaneol, (Z)-jasmone, α-damascenone, sclareololide, dihydroactinidiolide, vanillin, and δ-valerolactone), indicating that those compounds (OAV >1) were contributors to the overall aroma of Laoshan teas.
Small polymer particles with a diameter of less than 5 mm called microplastics find their way into the environment from polymer debris and industrial production. Therefore a method is needed to ...identify and quantify microplastics in various environmental samples to generate reliable concentration values. Such concentration values, i.e. quantitative results, are necessary for an assessment of microplastic in environmental media. This was achieved by thermal extraction in thermogravimetric analysis (TGA), connected to a solid-phase adsorber. These adsorbers were subsequently analysed by thermal desorption gas chromatography mass spectrometry (TDS-GC-MS). In comparison to other chromatographic methods, like pyrolyse gas chromatography mass spectrometry (Py-GC-MS), the relatively high sample masses in TGA (about 200 times higher than used in Py-GC-MS) analysed here enable the measurement of complex matrices that are not homogenous on a small scale. Through the characteristic decomposition products known for every kind of polymer it is possible to identify and even to quantify polymer particles in various matrices. Polyethylene (PE), one of the most important representatives for microplastics, was chosen as an example for identification and quantification.
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•Using a thermal decomposition method for analysing PE microplastics in environmental matrices in one step.•Direct measuring without a pre selection.•Identification and quantification of polymers in environmental samples.
Comprehensive two‐dimensional gas chromatography with mass spectrometry has been on the separation‐science scene for about 15 years. This three‐dimensional method has made a great positive impact on ...various fields of research, and among these that related to food analysis is certainly at the forefront. The present critical review is based on the use of comprehensive two‐dimensional gas chromatography with mass spectrometry in the untargeted (general qualitative profiling and fingerprinting) and targeted analysis of food volatiles; attention is focused not only on its potential in such applications, but also on how recent advances in comprehensive two‐dimensional gas chromatography with mass spectrometry will potentially be important for food analysis. Additionally, emphasis is devoted to the many instances in which straightforward gas chromatography with mass spectrometry is a sufficiently‐powerful analytical tool. Finally, possible future scenarios in the comprehensive two‐dimensional gas chromatography with mass spectrometry food analysis field are discussed.
Mercury (Hg) and its compounds are much concerned for their high toxicity and wide presence in the environment. Since the toxicity of Hg is species dependent, various methods have been developed for ...the speciation analysis of Hg. This review focus on the determination and speciation analysis of Hg chemical species in water, sediment, and soil samples. Recent developments on sample pre-treatment and extraction/pre-concentration, separation, and quantification of Hg chemical species, and associated analytical challenges have been reviewed and briefly discussed based on recent reports.
Mineral oil hydrocarbons (MOH) contain a wide structural diversity of molecules, for which the reference method of analysis is the online coupled liquid chromatography-gas chromatography with flame ...ionization detection (LC-GC-FID). These compounds are very heterogeneous from a toxicological viewpoint, and an accurate risk assessment when dealing with a MOH contamination can only be performed if sufficient information is available on the types of structures present (i.e., number of carbons, degree of alkylation, number of aromatic rings). Unfortunately, the separation performances of the current LC-GC-FID method are insufficient for such characterization, not even mentioning the possible coelution of interfering compounds which additionally hinder MOH determination. Comprehensive two-dimensional gas chromatography (GC × GC), while mostly used for confirmation purposes in the past, starts to prove its relevance for overcoming the weaknesses of the LC-GC method and reaching even better the analytical requirements defined in the latest EFSA opinion. The present paper therefore aims at highlighting how GC × GC has contributed to the understanding of the MOH topic, how it has developed to meet the requirements of MOH determination, and how it could play a role in the field for overcoming many of the current analytical and toxicological challenges related to the topic.
► LDS–VSLLME–GC–MS was applied to the determination of PEs. ► Low density and less toxic organic solvent toluene was used as extractant. ► Good extraction solvent dispersion was achieved by ...relatively less toxic surfactant combined with vortex agitation. ► Fast extraction time (within 1min) and high extraction efficiency with good enrichment factors up to 290 were achieved. ► The low-density organic solvent collection procedure was simple and fast.
For the first time, a novel low-density solvent-based vortex-assisted surfactant-enhanced-emulsification liquid–liquid microextraction (LDS–VSLLME) was developed for the fast, simple and efficient determination of six phthalate esters (PEs) in bottled water samples followed by gas chromatography–mass spectrometry (GC–MS). In the extraction procedure, the aqueous sample solution was injected into a mixture of extraction solvent (toluene) and surfactant (cetyltrimethyl ammonium bromide), which were placed in a glass tube with conical bottom, to form an emulsion by the assistance of vortex agitation. After extraction and phase separation by centrifugation, and removal of the spent sample, the toluene extract was collected and analyzed by GC–MS. The addition of surfactant enhanced the dispersion of extraction solvent in aqueous sample and was also favorable for the mass transfer of the analytes from the aqueous sample to the extraction solvent. Moreover, using a relatively less toxic surfactant as the emulsifier agent overcame the disadvantages of traditional organic dispersive solvents that are usually highly toxic and expensive and might conceivably decrease extraction efficiency to some extent since they are not as effective as surfactants themselves in generating an emulsion. With the aid of surfactant and vortex agitation to achieve good organic extraction solvent dispersion, extraction equilibrium was achieved within 1min, indicating it was a fast sample preparation technique. Another prominent feature of the method was the simple procedure to collect a less dense than water solvent by a microsyringe. After extraction and phase separation, the aqueous sample was removed using a 5-mL syringe, thus leaving behind the extract, which was retrieved easily. This novel method simplifies the use of low-density solvents in DLLME. Under the optimized conditions, the proposed method provided good linearity in the range of 0.05–25μg/L, low limits of detection (8–25ng/L) and good enrichment factors up to 290. The proposed method was successfully applied to the extraction of PEs in bottled water samples as a fast, efficient, and convenient method.
Introduction
Ssajuari‐ssuk and sajabal‐ssuk have many clinical benefits. It is difficult to discriminate between these two species based on general characteristics aside from the shapes of the ...leaves. Thus, species identification and quality control between ssajuari‐ssuk and sajabal‐ssuk are of great concern in plant science and clinical therapy.
Objective
The aim of this study is to determine whether fast gas chromatography with uncoated surface acoustic wave sensor (GC‐SAW) can be a useful technique for performing species identification and quality control using volatile patterns of ssajuari‐ssuk and sajabal‐ssuk air‐dried for 4 months and 2 years and 4 months.
Methodology
Fast GC‐SAW sensor provides second unit analysis, simple, on‐line measurements that do not require pretreatment of the sample and rapid sensory information. Headspace solid‐phase microextraction gas chromatography–mass spectrometry (HS‐SPME‐GC–MS) was employed to confirm the identification of the volatiles and compared to fast GC‐SAW sensor.
Results
In air‐dried sajabal‐ssuk, the concentration of 1,8‐cineole was higher than that in air‐dried ssajuari‐ssuk, while the level of α‐thujone was considerably lower than that of air‐dried ssajuari‐ssuk. Each of ssajuari‐ssuk and sajabal‐ssuk air‐dried for 4 months and 2 years and 4 months has its own characteristic volatile pattern owing to its individual chemotypes or chemical compositions.
Conclusion
Consequently, the fast GC‐SAW sensor can be a useful technique for species identification and quality control using volatile patterns of ssajuari‐ssuk and sajabal‐ssuk air‐dried for 4 months and 2 years and 4 months. This method can be used for the standardisation of quality control using volatile patterns of herbal medicines.
Consequently, the fast GC/SAW sensor can be considered a useful analytical method for species identification and quality control using the volatile patterns of ssajuari‐ssuk and sajabal‐ssuk that were air‐dried for 4 months (the first year) and 2 years and 4 months (the third year).
Chiral compounds are ubiquitous in nature and play a pivotal role in biochemical processes, in chiroptical materials and applications, and as chiral drugs. The analysis and determination of the ...enantiomeric ratio (er) of chiral compounds is of enormous scientific, industrial, and economic importance. Chiral separation techniques and methods have become indispensable tools to separate chiral compounds into their enantiomers on an analytical as well on a preparative level to obtain enantiopure compounds. Chiral gas chromatography and high‐performance liquid chromatography have paved the way and fostered several research areas, that is, asymmetric synthesis and catalysis in organic, medicinal, pharmaceutical, and supramolecular chemistry. The development of highly enantioselective chiral stationary phases was essential. In particular, the elucidation and understanding of the underlying enantioselective supramolecular separation mechanisms led to the design of new chiral stationary phases. This review article focuses on the development of chiral stationary phases for gas chromatography. The fundamental mechanisms of the recognition and separation of enantiomers and the selectors and chiral stationary phases used in chiral gas chromatography are presented. An overview over syntheses and applications of these chiral stationary phases is presented as a practical guidance for enantioselective separation of chiral compound classes and substances by gas chromatography.
This review article focuses on the development of chiral stationary phases for gas chromatography. The fundamental mechanisms of the recognition and separation of enantiomers and the selectors and chiral stationary phases used in chiral gas chromatography are presented. An overview over syntheses and applications of these chiral stationary phases is presented as a practical guidance for enantioselective separation of chiral compound classes and substances by gas chromatography.
Hotpot is a distinctive dish of East Asian cuisine, especially in China. Herein, headspace‐gas chromatography‐mass spectrometry, headspace‐gas chromatography‐ion mobility spectrometry, and sensory ...evaluation are applied to compare the volatile organic compounds (VOCs) of four types of hotpot seasoning oils (HSOs) and establish their characteristic fingerprints. A total of 203 VOCs are detected by gas chromatography‐mass spectrometry (GC‐MS). Among them, linalool, anethole, and estragole contribute to the overall aroma of all four HSOs (relative odor activity value ≥ 0.1). Gas chromatography‐ion mobility spectrometry (GC‐IMS) results reveal that 77 VOCs are identified, comprising 19 terpenoids, 18 aldehydes, 14 alcohols, 13 esters, 6 ketones, 3 acids, 2 furans, 1 pyrazine, and 1 sulfide. Meanwhile, principal component analysis demonstrates that GC‐IMS is an important tool for the rapid classification of hotpot seasonings. Finally, the sensory evaluation team concludes that the horse fat hotpot seasoning has promising development prospects. This study validates the applicability of GC‐IMS and GC‐MS for distinguishing VOCs in hotpots, and the findings provide a theoretical basis for flavor differentiation in HSOs.
Practical Applications: Horse oil is significantly lower in cholesterol than butter, and thus possesses potential benefits for human health. This study provides a basis to produce horse oil hotpots and a reference for identifying the VOCs in HSOs.
Commercially available vegetable hotpot seasoning oil (HSO), commercially available butter HSO, homemade butter HSO, and homemade horse oil HSO are detected and analyzed by gas chromatography‐mass spectrometry and gas chromatography‐ion mobility spectrometry (GC‐IMS) to compare the variation of volatile organic compounds (VOCs) in the four HSOs. Sensory evaluation is used for validation.
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