Two-dimensional Gas Research Articles

Comprehensive comparison of fatty acid methyl ester profile in different food matrices using microwave-assisted extraction and derivatization methods and comprehensive two-dimensional gas chromatography coupled with flame ionization detection

Analyzing fatty acids provides key insights into fat composition for industrial applications and their implications for nutrition and health. Typically, fatty acid analysis involves extracting lipids from the matrix and converting them into fatty acid methyl esters (FAME) through a derivatization process before gas chromatography (GC) analysis. Either one-step or two-step procedures can be found in the literature and as official methods. In this work, different methods exploiting microwave-assisted processes were compared with two official methods from the American Oil Chemical Society (AOCS). Especially, two types of microwave-assisted extractions were employed: solvent extraction and extraction with hydrolysis. The extracts were derivatized using either BF3 or a microwave-assisted methanolic hydrogen chloride solution. These combinations of extraction and derivatization methods were compared also with one-step microwave-assisted extraction and derivatization, and two AOCS reference methods, resulting in seven different methods applied to six different food matrices. The performance of the different procedures was compared based on the FAME profile obtained from the comprehensive two-dimensional GC (GC × GC)-FID analysis.Microwave-assisted processes were shown to be effective, yielding results comparable to the official methods in both the one-step and two-step methods. Moreover, it was shown that the BF3 derivatization could be safely replaced with microwave-assisted derivatization with methanolic hydrogen chloride, providing equivalent performances while enhancing operator safety and environmental friendliness. Some discrepancies in the FAMEs profile were highlighted for the sample of oats, the only explicitly requiring acidic hydrolysis for lipid extraction. Further studies are required to understand the reasons behind these differences and develop a suitable modified method. In conclusion, all the methods were evaluated for greenness and blueness with two specific tools: AGREEprep and BAGI.

Development of a Standardized Protocol for the Classification of Column Sets in Comprehensive Two-Dimensional Gas Chromatography

One-dimensional gas chromatography (1D-GC) stationary phases are generally classified according to their relative polarity into non-polar, semi-polar, and polar columns. In comprehensive two-dimensional gas chromatography (GC×GC), it is the polarity difference between the two tandem-assembled stationary phases that determines the selectivity of the column ensemble. This polarity difference is called orthogonality, and GC×GC column sets can be broadly categorized into four groups based on the direction of the serial coupling between the primary and secondary columns. A significant portion of the GC×GC column sets in use today are operated in forward-orthogonality mode, which means that the secondary column is more polar than the primary column. A growing number of reported GC×GC applications operate in reversed-orthogonality configurations, where the secondary column is less polar than the primary column. Very few examples exist of non-orthogonal column sets because of the fact that there is limited additional selectivity that the secondary column can offer over the separation that has already been achieved in the primary column when the two phases are either identical or close in polarity. The fourth group of GC×GC column sets, called hybrid orthogonality, involves the coupling of stationary phases with peculiar selectivity differences that manifest themselves in the bi-dimensional separation plots. In this work, we are presenting a normalized approach to GC×GC column set characterization that is based on the use of a reference mixture of standards called the Century Mix. The Century Mix contains 100 chemical probes of different functionalities that span a reasonable range of volatilities and polarities to capture the selectivity profile of any GC×GC column set. The Century Mix also contains important chemical probes that are used for 1D-GC column characterization (such as the Grob mix and the Rohrschneider/McReynolds compounds) to make some connections between the 1D-GC building block columns and the GC×GC column sets. We finally also outline some other important metrics of comparison that should be taken into consideration to assess the overall performance of a GC×GC system.

Optimization of headspace high-capacity tool coupled to two-dimensional gas chromatography–mass spectrometry for mapping the volatile organic compounds of raw pistachios. A proof-of-concept on the classification ability by geographic origin

An optimized procedure for extracting and analyzing raw pistachio volatiles was developed through headspace sampling with high-capacity tools and subsequent analysis using comprehensive two-dimensional gas chromatography coupled with mass spectrometry. The examination of 18 pistachio samples belonging to different geographic areas led to the identification of a set of 99 volatile organic compounds (VOCs). Molecules were putatively identified using linear retention index, mass spectra similarity, and two-dimensional plot location. The impact of preprocessing and processing techniques on the aligned data matrix from a set of samples of different geographical origins, after removing contaminants, was evaluated. The combination of scaling with log-transformation, normalization with z-score, and data reduction with random forest machine learning algorithm generated a panel of 16 discriminatory VOC molecules. As a proof of concept, raw pistachios' VOC profile was employed for the first time to tentatively classify them based on their geographical origin.

A gate tunable transmon qubit in planar Ge

Gate-tunable transmons (gatemons) employing semiconductor Josephson junctions have recently emerged as building blocks for hybrid quantum circuits. In this study, we present a gatemon fabricated in planar Germanium. We induce superconductivity in a two-dimensional hole gas by evaporating aluminum atop a thin spacer, which separates the superconductor from the Ge quantum well. The Josephson junction is then integrated into an Xmon circuit and capacitively coupled to a transmission line resonator. We showcase the qubit tunability in a broad frequency range with resonator and two-tone spectroscopy. Time-domain characterizations reveal energy relaxation and coherence times up to 75 ns. Our results, combined with the recent advances in the spin qubit field, pave the way towards novel hybrid and protected qubits in a group IV, CMOS-compatible material.

Exploring the chemogeographical variation of a commercially important medicinal tree (Prunus africana (Hook.f.) Kalkman) using a metabolomics approach

The stem-bark of Prunus africana (Hook.f.) Kalkman (African cherry) is traditionally used for the treatment of stomach ache, chest pain, malaria, fever, diabetes and high blood pressure. A large number of constituents have been isolated from the stem-bark including β-sitosterol and ursolic acid, which were reported to have anti-inflammatory activity. The aim of the study was to establish chemotypic variation among Prunus africana samples collected from three African countries, Cameroon, Democratic Republic of Congo (DRC) and Zimbabwe. Ninety-five stem-bark samples were collected from a total of nineteen populations, 11 in Cameroon (n = 55), 4 in Democratic Republic of Congo (n = 20) and 4 in Zimbabwe (n = 20). The samples were extracted with ethyl acetate, dichloromethane and methanol (1 g in 10 mL, 1 g in 10 mL and 2 mg in 5 µL, respectively). Chemometric analysis of chromatographic data obtained from high-performance thin layer chromatography (HPTLC), ultra performance liquid chromatography coupled with mass spectrometry (UPLC–MS), one-dimensional gas chromatography-time-of-flight-mass spectrometry (1D GC–ToF–MS) and spectroscopic data obtained from proton nuclear magnetic resonance (1H NMR) were done using MetaboAnalyst 4.0 software to explore chemotypic variation. A sample from each country was analysed by two-dimensional gas chromatography-time-of-flight-mass spectrometry (2D GC–ToF–MS) to resolve compounds that co-eluted in the 1D GC analysis. Quantification of selected compounds (β-sitosterol and ursolic acid) were done using a validated ultra performance liquid chromatography-photodiode-array detection (UPLC–PDA) method. The chemical profiles obtained from each of the four techniques were very similar for the samples from each country. The HPTLC profiles for Zimbabwe samples were distinctly different from the other two countries with a unique band at Rf value of 0.80. Multivariate analysis of the HPTLC data (using rTLC software), UPLC–MS, 1D GC–ToF–MS and 1H–NMR data revealed three clusters that were country specific. Chemometric analysis through the construction of PCA and a PLS–DA scores plots was performed, followed by the construction of variable important in projection plots, whereby marker compounds contributing significantly to the separation of the three clusters were selected and tentatively identified. Quantitative analysis revealed that samples from Zimbabwe contained higher levels of β-sitosterol (29.2 – 119 µg/g dry weight (DW) of the extract) compared to DRC and Cameroon, while samples from Cameroon were found to contain the highest levels of ursolic acid (1.80 – 141 µg/g DW of the extract). HPTLC, UPLC–MS, 1D and 2D GC–ToF–MS and 1H–NMR are valid tools for quality control of P. africana plant materials after revealing three clusters of samples collected from the three countries. Cameroon samples had high content of ursolic acid, while Zimbabwe samples showed high levels of β-sitosterol. The number of compounds detected across the three countries by 1D GC–ToF–MS was less compared to 2D GC–ToF–MS, which enhanced separation and resolution.

Screening for compounds with bioaccumulation potential in breast milk using their retention behavior in two-dimensional gas chromatography

Discovery of emerging pollutants in breast milk will be helpful for understanding the hazards to human health. However, it is difficult to identify key compounds among thousands present in complex samples. In this study, a method for screening compounds with bioaccumulation potential was developed. The method can decrease the number of compounds needing structural identification because the partitioning properties of bioaccumulative compounds can be mapped onto GC×GC chromatograms through their retention behaviors. Twenty pooled samples from seven provinces in China were analyzed. 1,286 compounds with bioaccumulation potential were selected from over 3,000 compounds. Sixty-two compounds, including aromatic compounds, phthalates, and phenolics etc., were identified with a high level of confidence and then quantified. Among them, twenty-seven compounds were found for the first time in breast milk. Three phthalate plasticizers and two phenolic antioxidants were found in significantly higher concentrations than other compounds. A toxicological priority index approach was applied to prioritize the compounds considering their concentrations, detection frequencies and eight toxic effects. The prioritization indicated that 13 compounds, including bis(2-ethylhexyl) phthalate, dibutyl phthalate, 1,3-di-tert-butylbenzene, phenanthrene, 2,6-di-tert-butyl-1,4-benzoquinone, 2,4-di-tert-butylphenol, and others, showed higher health risks. Meanwhile, some compounds with high risk for a particular toxic effect, such as benzothiazole and geranylacetone, were still noteworthy. This study is important for assessing the risks of human exposure to organic compounds.

Defining a core breath profile for healthy, non-human primates

Non-human primates remain the most useful and reliable pre-clinical model for many human diseases. Primate breath profiles have previously distinguished healthy animals from diseased, including non-human primates. Breath collection is relatively non-invasive, so this motivated us to define a healthy baseline breath profile that could be used in studies evaluating disease, therapies, and vaccines in non-human primates. A pilot study, which enrolled 30 healthy macaques, was conducted. Macaque breath molecules were sampled into a Tedlar bag, concentrated onto a thermal desorption tube, then desorbed and analyzed by comprehensive two-dimensional gas chromatography-time of flight mass spectrometry. These breath samples contained 2,017 features, of which 113 molecules were present in all breath samples. The core breathprint was dominated by aliphatic hydrocarbons, aromatic compounds, and carbonyl compounds. The data were internally validated with additional breath samples from a subset of 19 of these non-human primates. A critical core consisting of 23 highly abundant and invariant molecules was identified as a pragmatic breathprint set, useful for future validation studies in healthy primates.

Two-dimensional pair-interacting hole gas thermodynamics: Exactly solvable Moshinsky model for lens-shaped quantum dots

The thermodynamic characteristics of a pair-interacting hole gas localized in a Ge/Si lens-shaped quantum dot are studied. The pair-interaction potential is modeled by the oscillator function, which depends on the distance between the particles. The analytical form of the spectra makes it possible to calculate the partition function in Boltzmann approximation. Based on the partition function mean and free energies, heat capacity and entropy of the interacting gas are calculated. Interaction between particles substantially changes the behavior of the thermodynamic properties in comparison with the non-interacting gas case. In particular, the gas undergoes a first-order phase transition driven by the height of the upper (or lower) section of QD, resulting in a changing symmetry of the lens-shaped QD.

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.

Forensic significance of VOCs profiling in decayed ante- and post-mortem injuries by GC×GC-TOF/MS.

Accurately identifying and differentiating the types of injuries in decomposed corpses is a major challenge in forensic identification. Forensic investigations involving decomposed cadavers pose challenges in determining the cause of death. Traditional methods often lack conclusive evidence. However, the implementation of advanced analytical techniques, such as comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC-TOF/MS), shows promise in overcoming these limitations, but the potential in this area remains limited. Therefore, this study aims to bridge this gap by exploring the potential of GC × GC-TOF/MS in the analysis of volatile organic compounds (VOCs) changes within decaying ante- and post-mortem injuries.The research emphasizes the forensic significance of VOCs changes in decomposed cadavers. We used GC × GC-TOF/MS analysis to identify the specific volatile compounds in putrefied corpse tissue samples from mice. The GC × GC-TOF/MS analysis results showed that under winter conditions, PC1 explained 57.16% of the variance, and PC2 explained 25.23% of the variance; while under summer conditions, PC1 explained 71.89% of the variance, and PC2 explained 24.49% of the variance. This demonstrates the potential of GC × GC-TOF/MS in identifying specific VOCs present in tissue samples that can serve as potential biomarkers for distinguishing between antemortem and postmortem injury. GC × GC-TOF/MS analysis revealed distinct VOC patterns in both conditions. Comprehensive use of GC × GC-TOF/MS analysis enhances accuracy in identifying and characterizing ante- and post-mortem injuries in decomposed cadavers. This study can significantly contribute to the field of forensic medicine and improve the accuracy of forensic investigations.

The volatile oil of Hyssopus cuspidatus Boriss. (HVO) ameliorates OVA-induced allergic asthma via inhibiting PI3K/Akt/JNK/P38 signaling pathway and maintaining airway barrier integrity

Ethnopharmacological relevanceHyssopus cuspidatus Boriss., a classic Uyghur medicine, is used to treat inflammatory lung diseases such as asthma. But the therapeutic effect and mechanism of the volatile oil of Hyssopus cuspidatus Boriss.(HVO) in asthma therapy remain unclear. Aim of the studyWe aim to characterize the constituents of HVO, investigate the therapeutic effect in OVA-induced allergic asthmatic mice and further explore the molecular mechanism. Materials and methodsIn this study, we applied two-dimensional gas chromatography quadrupole time-of-flight mass spectrometry (GC × GC-QTOF MS) to identify the ingredients of HVO. We established OVA-induced asthmatic model to investigate the therapeutic effect of HVO. To further explore the potential molecular pathways, we used network pharmacology approach to perform GO and KEGG pathways enrichment, and then built an ingredient-target-pathway network to identify key molecular pathways. Finally, LPS-induced RAW 264.7 macrophages and OVA-induced asthmatic model were used to validate the potential signaling pathways. ResultsGC × GC-QTOF MS analysis revealed the presence of 123 compounds of HVO. The sesquiterpenes and monoterpenes are the main constituents. The in vivo study indicated that HVO suppressed OVA-induced eosinophilic infiltration in lung tissues, inhibited the elevation of IgE, IL-4, IL-5, and IL-13 levels, downregulated the expressions of phosphorylated PI3K, Akt, JNK and P38, and maintained epithelial barrier integrity via reducing the degradation of occludin, Zo-1, Zo-2, and E-cadherin. The in vitro study also revealed an inhibition of NO release and downregulation of phosphorylated PI3K, Akt, JNK and P38 levels. ConclusionHVO alleviates airway inflammation in OVA-induced asthmatic mice by inhibiting PI3K/Akt/JNK/P38 signaling pathway and maintaining airway barrier integrity via reducing the degradation of occludin, Zo-1, Zo-2, and E-cadherin.

A feasibility study of sample re-collection in the analysis of selected volatile compounds in breath samples using GC×GC-TOFMS

In this study, we aimed to assess the feasibility of re-collecting breath samples using the Centri® (Markes International, Bridgend, UK) followed by two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) analysis. The work was conducted in two main phases. In the first phase, we evaluated the re-collection performance by analyzing two sets of standards, including a Grob mix primary solution and a standard mixture of 20 selected volatile compounds (VCs) covering different classes of organic species commonly found in breath samples. The intra-day and inter-day precision (reported as relative standard deviation (RSD),%) for the re-collection of the Grob mix primary solution were in the range of 1 % to14 % and 3 % to12 %, respectively. The re-collection accuracy ranged from 78 % to 97 %. The intra-day RSD for the re-collection of the standard mixture of selected VCs was within 20 % for all compounds, except for acetone and nonane. The precision was within 25 % for all compounds, except for nonane, n-hexane, 1,4-dichlorobenzene, and decane, which exhibited less than 36 % RSD. The re-collection accuracy was in the range of 67 % to 129 %. In the second phase of the study, the re-collection performance in breath analysis was evaluated via five repetitive splitting and re-collection of six breath samples obtained from healthy adults, realizing a total of 30 breath analyses. Initially, we evaluated the re-collection performance by considering all features obtained from breath analysis and then focused on the 20 VCs commonly found in breath samples. The re-collection accuracy for total breath features ranged from 86 to 103 %, and the RSDs were in the range of 1.0 % to 10.4 %. For the selected VCs, the re-collection accuracy of all compounds, except for undecane and benzene, was in the range of 71 % to 132 %.

Accurate first-principles simulation for the response of 2D chemiresistive gas sensors

The realm of chemiresistive gas sensors has witnessed a notable surge in interest in two-dimensional (2D) materials. The advancement of high-performance 2D gas sensing materials necessitates a quantitative theoretical method capable of accurately predicting their response. In this context, we present our first-principles framework for calculating the response of 2D materials, incorporating both carrier concentration and mobility. We showcase our method by applying it to prototype NH3 sensing on 2D MoS2 and comparing the results with prior experiments in the literature. Our approach offers a thorough solution for carrier concentration, taking into account the electronic structure around the Fermi level. In conjunction with the mobility calculation, this enables us to provide a quantitative prediction of the response profile and limit of detection (LOD), yielding a notably improved alignment with prior experimental findings. Further analysis quantifies the contributions of carrier concentration and mobility to the overall response of 2D MoS2 to NH3. We identify that discrepancies in the charge-transfer-based method primarily stem from overestimating carrier concentrations. Our method opens exciting opportunities to explore carrier mobility-dominated sensing materials, facilitates efficient screening of promising gas sensing materials, and quantitative understanding of the sensing mechanism.

Impact of deodorisation time and temperature on the removal of different MOAH structures: a lab-scale study on spiked coconut oil

Vegetable fats and oils are prone to contamination by mineral oil hydrocarbons due to the lipophilic and ubiquitous character of the latter. As the aromatic fraction of these hydrocarbons, MOAH, is associated with carcinogenicity, mutagenicity, and detrimental effects on foetal development, finding strategies to limit or reduce their contamination is highly relevant. Deodorisation (i.e. a refining step) has shown the ability to remove MOAH < C25 in vegetable fats and oils, but there is little information about the structures removed. Therefore, the present study investigated the impact of deodorisation conditions on the removal of different structures of MOAH in spiked coconut oil. An inscribed central composite design was built with time and temperature as variables (0.5-4h, 150-240 °C), while pressure (3 mbar) and steam flow (1 g water/g oil per hour) were kept constant. The analysis of MOAH in the oil was performed using a fully automated liquid chromatography coupled with two parallel comprehensive two-dimensional gas chromatography systems with flame ionisation and time-of-flight mass spectrometric detection. Response surfaces plotting the MOAH loss according to time and temperature were built for different MOAH fractions. The latter were defined based on the number of aromatic rings (>3 or ≤3) and the number of carbon atoms present (C16-C20, C20-C24, C24-C35, C35-C40). It was found that at 200 °C, compounds < C24, including weakly alkylated triaromatics, could be reduced to below the limit of quantification, while at 230 °C, it was possible to remove >60% of the C24-C35 fraction, including pentaromatics of low alkylation.

Transition Metal (Cu, Pd, and Ag)-Modified Nb2S2C Monolayer for Highly Efficient Catechol Sensing: A First-Principles Investigation.

Motivated by recent advancements and the escalating application of two-dimensional (2D) gas or molecule sensors, this study explores the potential of the 2D Nb2S2C monolayer for detecting biomolecule catechol (Cc), whose excess concentration is highly dangerous to living beings. We use first-principles density functional theory (DFT) calculations to assess the Cc sensing performance of pure and transition metal (TM = Cu, Pd, Ag)-modified Nb2S2C monolayers. The Nb2S2C monolayer belonging to the new class of synthesized 2D materials, TM carbo-chalcogenides (TMCC), combines distinctive properties from both TM dichalcogenides and TM carbides and exhibits physisorption (-0.66 eV) toward the Cc molecule. Notably, the surface modifications with these TMs significantly enhanced the adsorption energy of Cc. The chemisorption of the Cc molecule on the Pd to Cu-modified monolayer is demonstrated with adsorption energies ranging from -1.09 to -1.3 eV and is due to the robust charge transfer and orbital interactions between the valence orbitals of TMs and Cc. In addition, the modification of the surface by TM leads to an increased work function sensitivity toward the Cc molecule. The study establishes the thermal stability at 300 K and dynamic stability of TM-Nb2S2C through ab initio molecular dynamics (AIMD) simulations and Phonon calculations, respectively. The theoretical estimation of achievable recovery time at 400 and 450 K for Pd and Ag and at 500 K for the Cu-modified Nb2S2C monolayer, respectively, confirms the potential practical application of the sensor for Cc detection. These compelling characteristics position the Nb2S2C monolayer as a promising nanomaterial for detecting Cc molecules in the environment.

Exploring the molecular characteristics of organic matter in low-rank coals using GC×GC/TOF-MS plus data mining

In-depth understanding the form of organic matter in low-rank coals contributes to the clean and efficient utilization of coals. Two low-rank coals were successively dissolved with cyclohexane, acetone and methanol at 300 °C, respectively. Six thermal dissolution (TD) extracts were comparatively analyzed using comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC×GC/TOF-MS). Cyclohexane tends to extract low-polar compounds inherent in coal, such as aliphatic hydrocarbons, arenes and phenols. Acetone can extract monocyclic aromatic hydrocarbons containing alkyl side chains. Meanwhile, acetone can form N-H⋯O hydrogen bonds with nitrogen-containing organic compounds (NCOCs), facilitating the extraction of a greater quantity of NCOCs. Methanol breaks the ArCH2OArR structural unit within coal molecules and forms the dominant alkyl-substituted phenol. It was revealed that sequentially TD at 300 °C using different solvents only breaks intermolecular forces and weak covalent bonds. Additionally, a series of isomers of tricyclic aromatic hydrocarbons and alkylphenols were authenticated by GC×GC/TOF-MS. Principal component analysis and hierarchical clustering analysis were applied to mine effective molecular information from the extensive MS data. The statistical results indicate that solvent had a significant impact on the structure and composition of the TD extracts, more so than the variations in coal species. Thus, the conjunction of GC×GC/TOF-MS and chemometrics provided methodological guidance for an enhanced comprehension of the molecular structure of coals.

Scale and conformal invariance in rotating interacting few-fermion systems

We show that rotating two-dimensional Fermi gases possess a nonrelativistic scale and conformal invariance at weak but nonzero interactions, where the scale invariance of universal short-range interactions is not yet broken by quantum effects. We demonstrate the symmetry in the excitation spectrum of few-fermion ensembles in a harmonic trap obtained by exact diagonalization. The excitation spectrum is shown to split in a set of primary states and derived excited states that consist of breathing modes as well as two different center-of-mass excitations, which describe cyclotron and guiding-center excitations of the total particle cloud. Furthermore, the conformal symmetry is manifest in the many-body wave function, where it dictates the form of the hyperradial component, which we demonstrate using Monte Carlo sampling of few-body wave functions. Published by the American Physical Society 2024

Comprehensive Analysis and Environmental Risk Assessment of Benzotriazoles in Airport Stormwater: A HS-SPME-GC × GC-TOF-MS-Based Procedure as a Tool for Sustainable Airport Runoff Water Management

Despite the numerous benefits of intensive air transport development, many activities associated with the operation of airports contribute to environmental pollution. The purpose of this research was the development, optimization, and validation of a headspace–solid-phase microextraction–comprehensive two-dimensional gas chromatography–time of flight–mass spectrometry (HS-SPME-GC × GC-TOF-MS)-based procedure for determining anti-corrosive compounds in airport stormwater. Optimized HS-SPME conditions include: 45 min extraction time, 100 °C temperature, 1.0 g salt addition, and 10 min desorption time at 270 °C. The developed procedure is sensitive, selective, accurate (recoveries ≥ 80.0%), and precise (the coefficient of variation (CV) ≤ 14.9%), making it a highly suitable tool for extensive airport stormwater quality monitoring. The validated analytical protocol was successfully used to detect pollutants, including 1H-BT, 4-MeBT, 5-MeBT, and 5,6-diMe-1H-BT, in stormwater from various European airports with different flight capacities. Throughout the sampling period at the investigated airports, 1H-benzotriazole was found in the highest concentrations, ranging from below the MQL to 467 mg/L. An ecotoxicological risk assessment revealed that 69% of the sites exhibited high risk levels (Risk Quotient ≥ 1). The developed procedure and carried out environmental risk assessments of benzotriazoles in airport stormwater enable an evidence-based approach to sustainable airport stormwater management.

Simultaneous discovery of compounds dominated by either molding kinetics or geographical region of origin for moisture damaged cacao beans using orthogonally applied tile-based fisher ratio analysis of GC×GC-TOFMS data

Herein, two “orthogonal” characteristics of moisture damaged cacao beans (temporally dependent molding kinetics versus the time-independent geographical region of origin) are simultaneously analyzed in a comprehensive two-dimensional (2D) gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) dataset using tile-based Fisher ratio (F-ratio) analysis. Cacao beans from six geographical regions were analyzed once a day for six days following the initiation of moisture damage to trigger the molding process. Thus, there are two “extremes” to the experimental sample class design: six time points for the molding kinetics versus the six geographical regions of origin, resulting in a 6 × 6 element signal array referred to as a composite chemical fingerprint (CCF) for each analyte. Usually, this study would involve initial generation of two separate hit lists using F-ratio analysis, one hit list from inputting the data with the six time point classes, then another hit list from inputting the dataset from the perspective of geographic region of origin. However, analysis of two separate hit lists with the intent to distill them down to one hit list is extremely time-consuming and fraught with shortcomings due to the challenges associated with attempting to match analytes across two hit lists. To address this challenge, tile-based F-ratio analysis is “orthogonally applied” to each analyte CCF to simultaneously determine two F-ratios at the chromatographic 2D location (F-ratiokinetic and F-ratioregion) for each hit, by ranking a single hit list using the higher of the two F-ratios resulting in the discovery of 591 analytes. Further, using a pseudo-null distribution approach, at the 99.9% threshold over 400 analytes were deemed suitable for PCA classification. Using a more stringent 99.999% threshold, over 100 analytes were explored more deeply using PARAFAC to provide a purified mass spectrum.

Safety assessment of polypropylene self-heating food container: The release of microplastics and volatile organic compounds

The safety assessment of food-contact plastic products is crucial for protecting consumers from potential harmful chemical contaminants. This study investigated novel contaminants and substances of concern in self-heating food containers, focusing on the release of microplastics (MPs) and the migration of volatile organic compounds (VOCs). Using micro-Raman spectroscopy, we simulated actual self-heating condition to determine the abundance, size, and size distribution of released MPs. Results showed MPs abundance ranging from 1.7 × 106 to 3.4 × 106 particles/L, with an average of 2.4 × 106 particles/L, where over 98 % of particles were smaller than 20 µm. For VOCs migration, we employed direct immersion solid-phase micro-extraction coupled with comprehensive two-dimensional gas chromatograph-tandem quadrupole-time-of-flight mass spectrometry (DI-SPME-GC×GC-QTOF-MS) under three migration conditions. We identified 41 VOCs, including saturated hydrocarbons, fatty acyls, organoxygen compounds, unsaturated hydrocarbons, benzene derivatives, and phenol ethers. Risk substances such as Dibutyl phthalate, Benzophenone, and 4-Methylbenzophenone were detected in three samples. Semi-quantitative analysis and toxicity classification revealed that the maximum migration of all analytes remained below corresponding limit values, indicating a generally low risk to consumers.