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Leachates from dumpsites have been known to pollute the environment with deleterious effects. The study examined the levels of the sixteen United States Environmental Protection Agency polycyclic aromatic hydrocarbons (PAHs) in leachates from an unlined solid waste dumpsite using a gas chromatography incorporated with a flame ionisation detector (GC-FID). Possible sources of the PAHs were identified using diagnostic pair ratios. Toxicity and mutagenic health-related risk were extrapolated. The average levels of PAHs ranged from 0.03–147.85 µg/L. The anthracene value of 147.85 µg/L was the maximum PAH concentration recorded. The lowest PAH observed was 0.03 µg/L, which was found in benzo(k)fluoranthene. The 3 – ring PAHs matrix was the highest PAH observed and it followed a ring size decreasing order of 3 > 4 > 5 > 2 > 6 in the leachate sample. The diagnostic pair ratio suggested mixed sources with a slightly dominant petrogenic source identified. The cluster analysis showed different sources of the congeners in the leachate. The benzo(a)pyrene toxic and mutagenic risk quotients showed that the greater concentrations of benzo(a)pyrene and dibenz(a,h)anthracene can induce carcinogenic and non-carcinogenic related health risks to a living organism. [ABSTRACT FROM AUTHOR]

Determining worker exposure to hazardous volatile organic compounds (VOCs) in air at levels exceeding the Permissible Exposure Limits and Recommended Exposure Limits established by the U.S. federal agencies of Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH), respectively, will continue to be an important part of environmental and occupational health risk assessments. The purpose of this work was to develop a reliable analytical method for rapid and on-site assessments of occupational VOC exposures using field-capable thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) instrumentation (i.e. the HAPSITE® ER). The experiments involved in this study included determining TD-GC-MS parameters suitable for efficient analyte separation and quantitation on the HAPSITE® ER, determinations of analyte mass loadings that cause mass spectrometer detector saturations, generation of calibration curves, estimations of the limits of detection (LODs) and quantification (LOQs), as well as desorption efficiency and relative response factor repeatability. The LODs using Carbopack™ B and Tenax® TA sampling media were estimated and ranged from 0.2–1.9 ng and 0.045–0.3 ng, respectively. The LOQs using Carbopack™ B and Tenax TA sampling media were estimated and ranged from 1.0–6.3 ng and 0.2–1.1 ng, respectively. We have developed a reliable analytical method for chloroform, benzene, trichloroethylene, and heptane using field-portable HAPSITE® ER instrumentation and Tenax® TA sorbent media. Reliable and accurate methods were developed for chloroform and trichloroethylene using Carbopack™ B sorbent media, however, this particular sorbent hadlow desorption efficiency and insufficient repeatability in relative response factors for many analytes. Our current and ongoing work in determining the uptake rates for analytes on Tenax® TA sorbent media will make the methods described herein applicable for on-site occupational VOC exposure assessments of chloroform, benzene, trichloroethylene, and heptane using either passive or active air sampling techniques. [ABSTRACT FROM AUTHOR]

In this study, quantitative and qualitative chromatographic analysis for the content measurements of sediments collected from the Gulf of Aqaba/Jordan-Red Sea and Tripoli Port/Lebanon-Mediterranean Sea, were carried out. Sediment hydrocarbon contents were examined by GC-FID. The outcomes showed that 16 hydrocarbons were quantified and identified. Dotriacontane, tritriacontane, hentriacontane, octacosane, heptacosane, pentatriacontane, docosane, tetracosane, and hexatriacontane displayed the major contents at the Gulf of Aqaba. Regarding Tripoli Port sediments; nonacosane, pentatriacontane, pentacosane, dotriacontane, heptacosane, docosane and tetratriacontane were detected. GC-FID data were exposed to PCA and HCA to reveal: the variations of sediment chemical profiles as a result of geographical areas, to show the hydrocarbons that were responsible for clustering, and finally, to facilitate the future profile prediction and areas clustering of unknown sediments based on their chemical profile. By HCA and PCA, the six sediment-origin samples of Aqaba were classified into three clusters; Industrial area alone due to the distinct content of dotriacontane, tritriacontane, hentriacontane and octacosane, Central Power Station, Tala Bay and Hotel Areas in one cluster which was related to the close content of heptacosane and finally the National Tourist Camp and Marine Science in one cluster since they have pentatriacontane with close levels. Regarding Tripoli Port sediment samples, the two clusters revealed that the Current Waste Dump along with the Wastewater Treatment Plant were grouped together, where the Fishing Port, Tripoli Harbour and the Closed Waste Dump areas were clustered in one group. Nonacosane and pentatriacontane were dominant to separate the Tripoli Harbour, Fishing Port area and the Closed Waste Dump, where pentacosane, dotriacontane, heptacosane, docosane and tetratriacontane were responsible to isolate the Wastewater Treatment Plant and the Current Waste Dump together. Classification of sediments based on GC-FID profile will accelerate the future profile prediction and origin-clustering of unknown sediment based on their profile. [ABSTRACT FROM AUTHOR]

The chemical composition of the essential oil of Lindera subumbelliflora (Lauraceae) was investigated for the first time. The essential oil was obtained by hydrodistillation and fully characterised by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The antifungal activity of L. subumbelliflora essential oil was tested against Candida albicans and Streptococcus mutans using the broth microdilution assay, whereas the microbial biofilms were determined using a semi-quantitative static biofilm. A total of 28 components (99.6%) were successfully identified, which were characterised by β-eudesmol (14.6%), cis-α-bergamotene (11.0%), α-copaene (8.5%), dodecen-1-ol (8.5%), and (E)-nerolidol (8.3%). The essential oil exhibited activity against Candida albicans and Streptococcus mutans with MIC values of 250 and 500 µg/mL, respectively. The essential oil increased the biofilm of Candida albicans by 38.25%, however, decreased the biofilm of Streptococcus mutans by 47.89% when treated with 500 µg/mL. Thus, the essential oil has a promising application in dentistry via inhibition of the growth of Candida albicans and Streptococcus mutans. However, the antibiofilm activity of the essential oil is only applicable for cariogenic Streptococcus mutans. [ABSTRACT FROM AUTHOR]

Acetohydroxyacid synthase (AHAS, EC 2.2.1.6) catalyzes the first step in the synthesis of the branched-chain amino acids valine, leucine, and isoleucine, pathways being present in plants and microorganisms, but not in animals. Thus, AHAS is an important target for numerous herbicides and, more recently, for the development of antimicrobial agents. The need to develop new and optimized herbicides and pharmaceuticals requires a detailed understanding of the biochemistry of AHAS. AHAS transfers an activated two-carbon moiety derived from pyruvate to either pyruvate or 2-oxobutyrate as acceptor substrates, forming 2-acetolactate or 2-acetohydroxy-2-butyrate, respectively. Various methods have been described in the literature to biochemically characterize AHAS with respect to substrate preferences, substrate specificity, or kinetic parameters. However, the simultaneous detection and quantification of substrates and unstable products of the AHAS-catalyzed reaction have always been a challenge. Using AHAS isoform II from Escherichia coli, we have developed a sensitive assay for AHAS-catalyzed reactions that uses derivatization with ethyl chloroformate to stabilize and volatilize all reactants in the aqueous solution and detect them by gas chromatography coupled to flame ionization detection or mass spectrometry. This assay allows us to characterize the product formation in reactions in single and dual substrate reactions and the substrate specificity of AHAS, and to reinterpret previous biochemical observations. This assay is not limited to the AHAS-catalyzed reactions, but should be applicable to studies of many metabolic pathways. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3) dissociation is of an initial and very important step during its combustion process. This study therefore systematically investigates the effect of reaction temperature (650–950 °C), fluidisation number (0.83–2.50) and static bed depth (0–25 mm) on NH 3 dissociation in a laboratory-scale Bubbling Fluidised Bed (BFB). By analysing the concentrations of H 2 and N 2 in the effluent using gas chromatography, results show that the conversion ratio of NH 3 in BFB was merely 0.26%–0.29% at 650 °C but increased significantly to 18.1%–25.3% at 950 °C. This highlights the importance of temperature in promoting NH 3 dissociation. However, as fluidisation number increased from 1.0 to 2.5, attributing to a decrease in gas – solid contact time, the conversion ratio of NH 3 decreased correspondingly from the highest 20.7%–5.7%. Moreover, as static bed depth increased from 15 mm to 25 mm, the conversion ratio of NH 3 increased slightly from 21.5% to 26.8%, both of which were found to be higher than that without bed particles. Clearly, NH 3 dissociation is enhanced by the bed material depth but is also dependent on the gas – solid contact time. In addition, by measuring the temperature distribution in the BFB reactor, a temperature drop of ca. 20 °C near the distributor was confirmed, showing a strong effect of endothermicity during NH 3 dissociation. These would provide an improved comprehension on the mechanisms of NH 3 dissociation and offer theoretical guidance for optimising the combustion processes in BFB burning NH 3. [Display omitted] • NH 3 dissociation at different temperatures and fluidisation numbers in BFB studied. • NH 3 conversion increased with temperature due to enhanced kinetic and heat transfer. • Increasing bed depth promotes NH 3 dissociation by increasing gas-solid contact time. • NH 3 conversion was the highest at incipient fluidisation but decreased at higher FN. • The endothermic NH 3 dissociation decreases bed temperature and hinders conversion. [ABSTRACT FROM AUTHOR]

Forest species are characterized by their wealth of essential oils (EOs), which play key requested for alternative control methods against weeds, fungi and pests. This study reports the chemical composition and highlight the antioxidant, antifungal and phytotoxic properties of the EOs obtained from Eucalyptus populifolia Desf, Eucalyptus woollsiana and Eucalyptus exserta. The EOs were analyzed by gas chromatography coupled to mass spectrometry (GC/MS). Their antioxidant, antifungal and phytotoxic properties were investigated. All EOs displayed a specific richness in eucalyptol (75.94-7.01%), camphene (6.97-0.4%) globulol (5.20-5.83%) and α-pinene (0.71-12.82 %). EOs isolated from E. populifolia exhibited significant antioxidant activity. Furthermore, all investigated EOs displayed significant antifungal properties against four phytopathogenic fungi belonging to Fusarium genus. The phytotoxic activity against five weeds showed varying effectiveness on seed germination and seedling growth, which exhibited greater effectiveness compared to glyphosate. Eucalyptus EOs have the potential to be used in the formulation of biopesticides. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the insecticidal properties of essential oil derived from Eucalyptus cinerea leaves and its main component, 1,8-cineole, against two significant pests of stored dates, Ectomyelois ceratoniae and Ephestia kuehniella (Pyralidae). The impact of the treatment on the sensory characteristics of date fruits was assessed to verify the complete absence of off-odours and off-flavours. Gas chromatography – mass spectrometry analysis of E. cinerea essential oil revealed that the primary compound was 1,8-cineole (74.5%). Fumigant toxicity of the two pests, indicated that first instar larvae (L1) exhibited greater tolerance to E. cinerea EO and 1,8-cineole than L5, while adult forms were more susceptible than larvae. The E. cinerea EO had a noticeable pest contact activity when used at a concentration of 0.35 µL/cm2 caused 100 and 88.3% mortality to E. ceratoniae and E. kueheniella, respectively, after 1 hour of exposure. Hedonic evaluation showed that consumers' appreciation of fumigated dates was not significantly different to the no treated dates. [ABSTRACT FROM AUTHOR]

A method for the analysis of trace nitrogen trifluoride impurities in high-purity carbon tetrafluoride (≥ 99.999%) by gas chromatography equipped with a flame ionization detector is described. A 10-port valve and three columns have been used in this instrument system, which can completely separate nitrogen trifluoride and carbon tetrafluoride. In the best analytical conditions, the quantification limit was estimated at 16.62 ppb for an injected sample volume of 1 mL. Furthermore, this method can be completed by one sample injection without the need to vent some of the main component-high-purity carbon tetrafluoride through the valve switch, which is more accurate and simple. [ABSTRACT FROM AUTHOR]

Retention prediction through Artificial intelligence (AI)-based techniques has gained exponential growth due to their abilities to process complex sets of data and ease the crucial task of identification and separation of compounds in most employed chromatographic techniques. Numerous approaches were reported for retention prediction in different chromatographic techniques, and consistent results demonstrated that the accuracy and effectiveness of deep learning models outclassed the linear machine learning models, mainly in liquid and gas chromatography, as ML algorithms use fewer complex data to train and predict information. Support Vector machine-based neural networks were found to be most utilized for the prediction of retention factors of different compounds in thin-layer chromatography. Cheminformatics, chemometrics, and hybrid approaches were also employed for the modeling and were more reliable in retention prediction over conventional models. Quantitative Structure Retention Relationship (QSRR) was also a potential method for predicting retention in different chromatographic techniques and determining the separation method for analytes. These techniques demonstrated the aids of incorporating QSRR with AI-driven techniques acquiring more precise retention predictions. This review aims at recent exploration of different AI-driven approaches employed for retention prediction in different chromatographic techniques, and due to the lack of summarized literature, it also aims at providing a comprehensive literature that will be highly useful for the society of scientists exploring the field of AI in analytical chemistry. [ABSTRACT FROM AUTHOR]

As a commonly well-known industrial chemical, phthalates are produced in high volumes to be used in various consumer products (e.g., plasticizers, medical devices, construction materials, and toys) to enhance softness, durability, transparency, and flexibility. Phthalates are generally not chemically bonded to the polymer chain of the plastic in which they are mixed. Thus, they may leach, migrate, or evaporate into indoor/outdoor air, and foodstuffs. In this review, a comprehensive overview of several sample preparation methods coupled with gas chromatography for the analysis of phthalates in various kinds of complex matrices, with a focus on the last 20 years' worth of papers. The review begins by highlighting the environmental significance of phthalate pollution along with the various routes to their exposure to general population. Then, the discussion is extended to cover the pretreatment and extraction techniques for phthalates for their quantitation based on gas chromatographic approach. Finally, the present and future challenges for the detection of phthalates in aqueous and food matrices are discussed. [ABSTRACT FROM AUTHOR]

Since its introduction comprehensive two-dimensional gas chromatography (GC × GC) has been widely applied to analyze complex samples due to its enhanced peak capacity and selectivity, thereby increasing the number of identifiable peaks and improving coelution issues. Even though it is still undergoing development, GC × GC provides many advantages in the analysis of petroleum-derived samples, whether in reservoir geochemistry applications or in environmental studies associated with spilled oils. In general, it facilitates more thorough fingerprinting and compositional evaluation. In environmental studies, it helps enhance understanding of weathering processes and the environmental behavior of hydrocarbons, as its chromatographic retention indices can robustly estimate liquid vapor pressures, aqueous solubility and other physical chemical properties. This review presents a brief history of GC × GC instrumentation, discussing recent and significant advances in petroleum applications, from data handling techniques to reservoir geochemistry and environmental forensics, as well as some specific advantages achieved and certain limitations that continue to be encountered. [ABSTRACT FROM AUTHOR]

Chlorination of seawater forms a range of secondary oxidative species – collectively called "chlorine-produced oxidants" (CPOs) – having different biocidal, environmental and ecotoxicological properties. The chemical speciation of these compounds is an important step in attempts to assess the effectiveness of chlorination and the potential impacts of its releases. However, comprehensive determination of CPOs represents a significant analytical challenge for many reasons, including the following: CPO species are numerous, highly reactive, with short-lifetimes, difficult to isolate and generally present at low concentrations in a complex salt matrix. Literature review reveals the development of a wide variety of analytical approaches for analysis of CPOs, either collectively via group parameters or individually. A first category of these approaches was the subject of article II (also including sampling and sample preparation) of a trilogy devoted to the chemical speciation of CPOs in seawater. In this third article – which closes the trilogy – emphasis is placed on chromatographic- and mass spectrometric-based approaches. It reviews more than 80 methods, reported from 1981 to date, and thoroughly discusses their principles and performances. Methodologies involving chemical derivatization of CPOs prior to their analysis by gas or liquid chromatography coupled to mass spectrometry provide the best sensitivities, achieving sub-ppb detection limits for species for which suitable derivatization reagents are available. Online mass spectrometry approaches are attracting increasing interest for their ability to analyze multiple CPO species in real time without extensive sample preparation steps, reaching detection limits of about ppb for less polar oxidants. At the current state of metrological development, neither the methodologies based on chromatography nor those based on online mass spectrometry allow complete speciation of CPOs. Future trends and major challenges related to these approaches are discussed. [ABSTRACT FROM AUTHOR]

This study investigated the effects of halibut oil cream, containing omega-3 fatty acids, vitamins A and D, and hydroxyproline, on burn wound healing in rats. Acute dermal toxicity tests confirmed its nontoxicity. Wistar rats were divided into five groups: a control, a positive control treated with silver sulfadiazine 1% (SSD), and three groups treated with 3%, 9%, and 27% halibut oil cream Formulation (HBOF). The SSD and HBOF groups showed significant healing improvements compared to the control. Histopathological analysis indicated increased collagen production in the HBOF groups, suggesting halibut oil cream's potential as a topical treatment for burn wounds. [ABSTRACT FROM AUTHOR]

BACKGROUND: Quercitrin is a dietary flavonoid widely found in plants with various physiological activities. However, whether quercitrin alters gut microbiota in vivo is not well understood. The aim of this study was to investigate metabolism of quercitrin in the colon and its regulation on gut microbiota in mice. RESULTS: Herein, 22 flavonoids related to quercitrin metabolism were identified based on ultra‐performance liquid chromatography‐electrospray ionization‐tandem mass spectrometry (UPLC‐ESI‐MS/MS). Gas chromatography and 16S rDNA gene sequencing were used to investigate short‐chain fatty acid (SCFA) content and diversity of composition of gut microbiota, respectively. The results showed that quercitrin significantly alters the beta‐diversity of the gut microbiota, probiotics such as Akkermansia and Lactococcus were significantly increased, and the production of propanoate, isovalerate and hexanoate of the quercitrin group were enhanced significantly. The Spearman's association analysis provided evidence that Gardnerella and Akkermansia have obvious correlations with most of quercitrin metabolites and SCFAs. CONCLUSION: Quercitrin and its metabolites in the colon altered the structure of the mice gut microbiota and increased the content of SCFAs. Our experiments provide valuable insights into quercitrin research and application. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Birch tar was the first substance made by humans that is otherwise not available in nature. The oldest artefacts date to ~ 200 thousand years ago in Europe but birch tar becomes more frequent around 45 thousand years ago and even more so from the Mesolithic onwards. Their study has important implication for our understanding of evolutionary processes such as cognitive capacity and cultural evolution. What remains unknown is the overall molecular composition of birch tar. Several approaches based on gas chromatography-mass spectrometry have shown the potential of studying solvent soluble molecules to understand the botanical origin of different tars, their manufacturing techniques and their post-depositional alteration mechanisms. However, birch tar's soluble fraction cannot shed light on its mechanical properties. In this study, we conduct gas chromatography-mass spectrometry and spectroscopic analysis of seven bulk birch tar samples, including infrared band assignment and structural refinement of organic molecules in the insoluble fraction. We find that the overall proportion that cannot be analysed by gas chromatography accounts for 85–90% in birch tar. This phase consists of polymerised molecules with a structure analogous to asphaltenes but containing a significantly greater amount of oxygen-related functional groups. Our findings have implications for understanding the viscosity, adhesiveness and stiffness of birch tar and they call for caution in applying analytical techniques that only target soluble molecules in birch tar. [ABSTRACT FROM AUTHOR]

Currently, precise and accurate measurements of CO2 emissions are essential for obtaining valid and reliable monitoring data, which serve as the basis for decision-making by environmental policy makers. In this study, method validation was carried out to measure CO2 at emission concentrations (1000 μmol/mol and 2.8% mol/mol) using gas chromatography with a thermal conductivity detector (GC-TCD). Various parameters of method validation, such as selectivity, limit of detection (LoD), limit of quantification (LoQ), accuracy, precision, linearity, and ruggedness, were investigated thoroughly. The results showed that the GC-TCD method demonstrated good repeatability and intermediate precision, with a % relative standard deviation less than 0.2%, while the bias method had a value between ± 2σ (σ: precision of laboratory result). The relative expanded uncertainty estimations are approximately 0.5% and 0.8% for CO2 measurements of 2.8% mol/mol and 1000 µmol/mol, respectively. The validated in-house method of GC-TCD is found to be precise, accurate, and fit for the purpose of measuring CO2 gases in the N2 matrix and capable of quantifying CO2 emission levels (1000 µmol/mol and 2.8% mol/mol). [ABSTRACT FROM AUTHOR]

In this study, the catalytic (co‐)pyrolysis of low‐density polyethylene (LDPE) and polyethylene terephthalate (PET) with HZSM‐5 and HY zeolite catalysts was conducted in a micro‐pyrolysis reactor coupled to a two‐dimensional gas chromatography system. Pyrolysis operating conditions, such as the pyrolysis temperature, the catalyst to feedstock (CF) ratio, and the LDPE:PET ratio, were varied. It was found that for the co‐pyrolysis of LDPE and PET, HZSM‐5 led to higher yields of C2‐C4 olefins and monoaromatic products. Lower CF ratios increased the yield of C2‐C4 olefins for LDPE pyrolysis, but decreased benzene yield for PET pyrolysis, concomitant with an increased yield in benzoic acid. A lower temperature of 400°C which was sufficient for the pyrolysis of LDPE, led to incomplete conversion of PET. Surface response diagrams were used to visualize the impact of the various pyrolysis operating conditions on the yield of C2‐C4 olefins and BTEX, which serve as target products for the circular economy. [ABSTRACT FROM AUTHOR]

The aim of the present study was to investigate the feasibility and applicability of Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (FT-IR-ATR) techniques, without extraction, with prior extraction of fat and after hydrolysis and methylation, to fatty acid methyl esters (FAME) to evaluate the content of trans fatty acids (TFA) in filled biscuits and to compare the results obtained with those obtained when elaidic acid was determined by the GC–MS technique. Eight commercial brands of chocolate filled biscuits and one package of hydrogenated vegetable fat were selected to be used as secondary standards by FT-IR-ATR. The presence of TFA was identified by FT-IR-ATR by visualization of the band at 966 cm−1. No significant differences were found between the concentrations of TFA determined by the three methods tested. The study indicated that the FT-IR-ATR technique, when used to analyze the lipid extract and the samples in the form of FAME, is suitable for estimating the TFA content in chocolate filled biscuits. [ABSTRACT FROM AUTHOR]

In order to determine the chemical composition of peat, the individual composition of lowland peat from the Bolshoi Kaltus 1 deposit (Arkhangelsk oblast) was characterized. The chemical composition of pyrolysis products of the test peat sample was determined using pyrolytic gas chromatography (GC–MS). Chromatograms of peat were obtained at temperatures from 200 to 600°C. The paper presents the results of a study of the peat pyrolysis process. The properties of products obtained on its basis by thermochemical treatment were described. [ABSTRACT FROM AUTHOR]

The potential application of microwave technology and interaction with oil/catalysts for heavy naphtha cracking to light products (aromatics and olefines) was explored. The reactor is a QVF tube of 240 mm long and 12.7 mm inner diameter, with 80 mm effective zone and the upper and lower zones filled with inert ceramic particles. The process used heater for heating heavy naphtha and condenser for the gas products. The feed enters the reactor after heating and the reaction occur within the catalytic zone while the ceramic particles improve the distribution of the compounds of the feed and products. All the products condensed and analysed by gas chromatography. Microwave technique used in chemical reactions in order to save energy and increase the conversion with lower temperature due to hot spots created within the catalyst. ZSM-5 (10) catalysts cracking experiments performed with and without nitrogen injection. The nitrogen injection increased the conversion in all conditions. The experiments achieved with various microwave irradiation (750-1250) W, preheating temperatures (150-250 °C) and space velocities (2 and 6 l/hr). The best result of cracking reaction conversion is (77.56%) at microwave power of (1250 W), a flowrate of (2 l/hr) and preheating temperature (200 °C). The cracking is facilitated due to re-activation effect of nitrogen on acid sites of the catalyst. The time of experiment is 12 minutes. Almost the flowrate has negative effect on the conversion. Microwave power increase reaction rate and increased the reaction conversion compared with conventional techniques. This study covered the effect of microwave with catalyst on the residence time, energy saving and conversion at lower temperature. [ABSTRACT FROM AUTHOR]

Methane pyrolysis is a promising method for producing low-carbon hydrogen, but a major challenge is the reactor clogging with soot. This study investigates methane pyrolysis in a corundum tube with a diameter of 50 mm and a working zone length of 300 mm. Rotating the tube with ceramic balls to clean the reactor space from soot deposits was proposed. Experiments were conducted at temperatures of 1200 °C, 1300 °C, and 1400 °C with methane flow rates of 0.3, 0.5, 0.7, and 0.9 m³/h. The gaseous pyrolysis product was analyzed using gas chromatography, and soot was studied using SEM, BET, X-ray diffraction, Raman spectroscopy and Pyrolytic GC-MS methods. As the pyrolysis temperature increased from 1200 to 1400 °C, the hydrogen yield increased from 50.08% to 75.10% and from 13.32% to 57.34% at methane flow rates of 0.3 and 0.9 m³/h, respectively. Analysis of pyrolysis byproducts revealed the presence of monosubstituted benzenes and polycyclic arenes and their isomers. The size of soot particles obtained in the tube ranged from 140 to 800 nm. Soot particles from the corundum ball had a broader size range of 230–570 nm, while particles from the zirconium dioxide ball ranged from 320 to 450 nm. The best result was an experiment lasting 4 h and 30 min, with an average hydrogen concentration in the pyrolysis products of 43 vol%. The experimental parameters were: temperature 1200 °C; methane flow rate 0.3 m³/h; 120 ml of zirconium dioxide balls; tube rotation speed 20 rpm. • Methane pyrolysis in the corundum tube was studied at 1200–1400 °C. • Rotating the tube with ceramic balls to clean the reactor space from soot deposits was proposed. • As the pyrolysis temperature increased from 1200 to 1400 °C, the hydrogen yield increased from 50.08% to 75.10%. • Hydrogen yield increased from 13.32% to 57.34% at methane flow rates of 0.3 and 0.9 m³/h. [ABSTRACT FROM AUTHOR]

The NIST gas chromatographic retention index database is widely used in gas chromatography–mass spectrometry analysis. For many compounds, the NIST database contains many entries that are presumably obtained independently of each other. We showed with specific examples that there are cases in the NIST database where several entries exist for the same compound, and all of them are equally erroneous (an error of more than 100 units). In particular, we demonstrated that all retention index values for such an important compound as imidazole for non-polar stationary phases in the NIST database are erroneous. In addition to imidazole, a similar situation is observed for four more nitrogen-containing heterocyclic compounds. For certainty, measurements were performed under several conditions, using various temperature programs, and using two specimens of columns. The structures were confirmed using nuclear magnetic resonance and mass spectrometry. It was shown with specific examples that many values are not reliable: either data were obtained using standard samples of undescribed origin without confirmation (without even using mass spectrometry) or, in some cases, standard samples were not used at all, and the retention index was obtained for a mixture component identified using a mass spectral library search. Some "independent" values are not such but are repeated publications of the same data (secondary sources), or simply several values taken from the same source. In the work, an analysis was carried out and assumptions were made about how several equally incorrect retention index values could appear in the NIST database. [ABSTRACT FROM AUTHOR]

Fluorinated organic compounds (FOCs) represent a class of synthetic chemicals distinguished by their resilient carbon–fluorine bonds, which demonstrate an ability to withstand environmental degradation over an extended period. The integration of FOCs into cutting-edge applications, including lithium-ion batteries (LiBs), presents considerable potential for environmental harm that has not yet been sufficiently addressed. This study focuses on the environmental fate of two fluorinated aromatics, tris(pentafluorophenyl)borane (TPFPB) and tris(pentafluorophenyl)phosphine (TPFPP), given their important role in improving the performance of LiBs. To achieve this, laboratory simulation methods including total oxidizable precursor assay, electrochemistry (EC), Fenton reaction, UV-C irradiation, and hydrolysis were employed. Liquid chromatography and gas chromatography coupled with high-resolution mass spectrometry were used for identification of transformation products (TPs) and prediction of their molecular formulae. Despite the structural similarity between TPFPB and TPFPP, distinct differences in electrochemical behavior and degradation pathways were observed. TPFPB readily underwent hydroxylation and hydrolysis, resulting in a wide range of 49 TPs. A total of 28 TPs were newly identified, including oligomers and highly toxic dioxins. In contrast, TPFPP degraded exclusively under harsh conditions, requiring the development of innovative conditioning protocols for EC. In total, the simulation experiments yielded nine structurally different compounds, including seven previously undescribed, partially defluorinated TPs. This study highlights the potential risks associated with the use of FOCs in LiBs and provides insight into the complex environmental behavior of FOCs. [ABSTRACT FROM AUTHOR]

ABSTRACT The efficiency and influencing factors during PAH‐polluted soil remediation by dielectric barrier discharge (DBD) low‐temperature plasma technology are investigated in this study. Gas chromatography, microbial community structure analysis, and response surface analysis were used to optimize suitable remediation processing factors. The degradation rates of phenanthrene and benzo[a]pyrene reached 94.37% and 86.53%, respectively, at an initial concentration of 100.00 mg/kg, whereas optimal parameters for the system were identified as 130 V for voltage, 160 Hz for frequency, 0.60 L/min for gas flow rate, and 40 min for discharge time. Comprehensively, DBD plasma is an efficient, low‐energy, and sustainable remediation technology according to the energy consumption calculation and comparison with the relevant literature. [ABSTRACT FROM AUTHOR]

This article presents a thorough examination of research on the onion lachrymatory factor (LF), covering aspects such as its structural determination, confirmation of stereochemistry, formation pathways, analytical methods, and its impact on onion flavor. Identified as the onion LF, propanethial S-oxide primarily adopts a (Z)-configuration and is generated through the enzymatic breakdown of its precursor, (+)-S-(E)-1-propenyl-L-cysteine S-oxide, with alliinase serving as the catalyst. Following this, an isomerization process takes place involving an intermediate compound, (E)-1-propenesulfenic acid, catalyzed by lachrymatory factor synthase. To address challenges in conventional gas chromatography (GC) analysis posed by high temperatures, alternative methods such as UV spectroscopy, chemical derivatization, GC with cold injection, high-performance liquid chromatography, direct analysis in real-time mass spectrometry, proton-transfer reaction-mass spectrometry, and secondary electrospray ionization high-resolution orbitrap mass spectrometry have been employed for qualitative and quantitative LF analysis. Beyond its tear-inducing properties, LF significantly contributes to the distinctive onion flavor. This review is crucial for advancing our understanding of the onion LF and sulfur-containing flavor components in the Allium vegetable family. It helps for improving the flavor of onions and refining various onion varieties. [ABSTRACT FROM AUTHOR]

Background: 3,3'-diindolylmethane (DIM) is a phytonutrient derived from cruciferous vegetables that is an often-used supplement in the complementary and alternative medicine space. The most common goal for providers when recommending DIM to their patients is to alter estrogen metabolism, yet research into DIM's effect on the estrogen profile is lacking in the published literature. The objective of this study was to comprehensively evaluate DIM's effect on the urinary estrogen profile. Methods: In this retrospective cohort study, we analyzed data from a clinical laboratory, including urinary estrogen and estrogen metabolite concentrations. Analyte concentrations were determined from dried urine samples using a gas chromatography-tandem mass spectrometry assay. Individuals were separated into two groups, either reporting taking DIM (N = 909) or reporting not taking DIM (N = 18,385). Comparisons between individuals in these two groups were made using the Wilcoxon rank sum test. Additionally, we were also able to explore a subset of women who had laboratory results in the database before and after initiating DIM treatment (N = 53). In this subset, differences were assessed with Wilcoxon signed rank tests. Results: In the larger group that was separated into women reporting either DIM use or no use, significant differences were observed in the concentrations of almost every urinary estrogen and estrogen metabolite (with the only exception being 2-methoxyestrone) in the urinary estrogen profiles of those taking DIM compared to those not taking DIM (all P values < 0.001). In the smaller subset of individuals with results before and after initiating DIM use, differences were only seen in 4 of the urinary estrogens and estrogen metabolites (P < 0.001 for estrone, estradiol, estriol, and 16-hydroxyestrone). Differences in total estrogens were significant in both the larger group and the smaller subset (both with P < 0.001). Additionally, observed differences in the ratios of metabolites followed a similar trend with more significant differences observed in the larger group. Notably, the 2-hydroxyestrone:16-hydroxyestrone ratio increased significantly in both the larger group and the smaller subset with results before and after DIM use. Conclusions: The results of this study provide the most comprehensive evaluation to date of DIM's effect on the urinary estrogen profile. Additionally, the results demonstrate that the dried urine collection and accompanying assay used capture changes that are similar in direction, but not necessarily magnitude, to previous reports in the literature. Considered together, these two things highlight the clinical validity and utility of this approach to the evaluation of DIM supplementation and suggest the need for additional studies using this approach to fully understand the potential clinical utility of DIM. [ABSTRACT FROM AUTHOR]

With increasing attention to alternative energy sources due to environmental concerns, biomass emerges as a promising solution. However, biomass combustion emits particulate matter and harmful substances, impacting air quality and human health. The study compares gas chromatography‐mass spectrometry (GC‐MS) and high‐performance anion‐exchange chromatography with pulsed amperometric detection (HPAEC‐PAD) methods for biomass combustion marker determination. GC‐MS involves derivatization and subsequent analysis, while HPAEC‐PAD utilizes water extraction, bypassing derivatization. Both methods' analytical performance characteristics were compared, showing HPAEC‐PAD to have slightly lower detection limits and simplified sample preparation. The comparison revealed similar concentrations of levoglucosan and mannosan between the methods. However, galactosan (GA) concentrations showed discrepancies, possibly due to method sensitivity and recovery. HPAEC‐PAD exhibited advantages in GA detection due to its direct analysis and better recovery. The study highlights the suitability of HPAEC‐PAD for biomass combustion marker analysis, especially for GA determination, owing to its simplicity. However, GC‐MS offers advantages in complex matrix identification. The findings provide insights for future research on atmospheric aerosol analysis and comparative studies of analytical techniques for other monosaccharides. [ABSTRACT FROM AUTHOR]

Separation of ethanol/water or benzene/methanol azeotrope mixtures presents significant challenges, not only due to the limitations of conventional distillation techniques but also because of the constraints in developing and utilizing of new generation adsorbents. Porous organic molecular frameworks constructed via noncovalent π‐interactions are emerging as novel adsorbents with vast potential in gas adsorption and molecular separation. Herein, we report a permanent two‐dimensional porous structure, namely TDTBA‐1, which consists of two different kinds of pores through π‐stacking of a single organic molecule with highly Td symmetry. Activated TDTBA‐1 exhibits excellent hydrophobicity, thermal stability, recoverability and high selectivity for ethanol over water, and benzene over methanol. Therefore, activated TDTBA‐1 can be used as an efficient stationary phase for the separation of ethanol/water and benzene/methanol azeotropes by high‐resolution gas chromatography. [ABSTRACT FROM AUTHOR]

AbstractMitigation of the environment from hazardous pesticides is clamant for all living things. The behavior of the fungicide Fuberidazole was investigated toward biodegradation. Biotransformation experiments were conducted by bacterial strains isolated from soils including, Xanthomonas citri (XC), and Pseudomonas syringae (PS), and fungal strains including, Aspergillus flavus (AF), Aspergillus niger (AN) and Penicillium chrysogenum (PC). Analysis and quantification of Fuberidazole degradation and its metabolites were performed by gas chromatography mass spectrometry and UV-visible spectrophotometry. Pseudomonas syringae and Penicillium chrysogenum displayed great bioremedial potential and degraded 91 and 86% of Fuberidazole after 35 days. Significant metabolites such as Benzimidazole 2-carboxylic acid, Benzimidazole, and 1-(1H-benzimidazole-2-yl)ethanone were produced in the current experiment. The increasing order of half-life for all strains was obtained as, PS (10.3) < PC (10.6) < AN (11) < AF (11.9) = XC (11.9) days. Experimental results demonstrated the capability of bacterial cells to efficiently utilize Fuberidazole as a nutrition source and the significance of favorable environmental conditions for its dissipation. [ABSTRACT FROM AUTHOR]

The use of pesticides is often regarded as a fundamental aspect of conventional agriculture. However, these compounds have gained recognition as some of the oldest and most widely employed xenobiotic contaminants, necessitating effective strategies for human biomonitoring. In this context, a method was developed for the determination of 16 legacy organochlorine pesticides, 6 metabolites of current pesticides (2,4-D, malathion, parathion, fipronil, pyraclostrobin, cypermethrin, permethrin, cyfluthrin), and 1 triazine herbicide (atrazine) in serum. Samples were prepared with water, formic acid, acetonitrile, and ultrasound irradiation, followed by solid-phase extraction with Oasis Prime HLB. Subsequently, metabolites from current pesticides underwent derivatization using MTBSTFA with 1% TBDMSCl for analysis via gas chromatography-tandem mass spectrometry (GC–MS/MS), employing an SLB-5MS fused silica capillary column. Analytical curves were generated with limits of quantification from 0.3 to 4.0 ng.mL−1. Accuracy ranged from 69 to 124%, and the coefficient of variation from 2 to 28%. Moreover, determining 1-(4-chlorophenyl)-1H-pyrazol-3-ol was suggested as a biomarker for pyraclostrobin biomonitoring. This analytical approach facilitated the determination of both legacy and metabolites of current pesticides in the same serum sample, presenting an interesting and cost-effective option for large cohorts, and multi-omics studies that evaluate time-dependent biomarkers in blood samples, thereby enabling biomonitoring within the same matrix. Furthermore, a proof-of-concept involving 10 volunteers demonstrated exposure to 9 pesticides at mean concentrations measured in ng mL−1, consistent with findings from various biomonitoring initiatives. [ABSTRACT FROM AUTHOR]

The request for novel hyphenated instruments and techniques, capable of affording exhaustive information and results, is a focus continuously watched out. In this context, the present work aimed at the development of an integrated system combining gas chromatographic (GC) separation with mass spectrometry (MS) and (solid deposition) Fourier transform infrared spectroscopy (FTIR) detection. An external transfer line was designed in the lab for the parallel coupling of the two detectors, in such a way to obtain complementary analytical information consisting of an MS spectrum, an IR spectrum and linear retention indices (LRI), within a single analysis. The instrument performance was demonstrated for the analysis of a commercial mixture consisting of 139 hydrocarbons, comprising linear, branched, unsaturated and aromatic compounds. A 100-m poly(dimethylsiloxane) column was employed for the separation, and the outlet flow was split 95:5 between the IR and MS detectors using two uncoated capillaries. The IR spectra were acquired from solid deposits on a zinc selenide disc (−90 °C), over a spot (detector area) of about 0.1 mm2, in the range of 4000–700 cm−1 and at a resolution of 4 cm−1. Final identification of the separated compounds by a library search was achieved by excluding incorrect results, sequentially using a three-filter approach (85% similarity against reference MS and IR library spectra and ±10 LRI unit tolerance). Based on these preliminary results, the GC-MS/sd-FTIR system is a promising tool for the characterization of complex matrix constituents, for which identification is cumbersome, by using only one detection technique. [ABSTRACT FROM AUTHOR]

The aromatic profile of red wines is influenced by various factors, among them being distinguished the pedoclimatic ones, the variety, or the production technology. In the winemaking process, the use of different yeast strains can lead to obtaining wines with specific or conventional aromas (commercial strains), but also to the production of wines with a regional character using local strains. This study focuses on the analysis and comparison of the compounds that offer aromas in five wine varieties (Pinot noir, Feteasca Neagra, Burgund Mare, Syrah, and Novac) from Recaș, Romania, obtained through microvinification under the influence of several types of starter strains (Enartis Ferm SC, Viniferm Sensacion, SCR297, SCR462). The concentrations of polyphenols and anthocyanins, as well as their antioxidant activity, were monitored, resulting in significant values, mainly using autochthonous strains isolated from local plantations. A total of 30 aroma compounds were identified, maximum amounts being noted in the assortments where SCR297/SCR462 yeasts were used within the fermentation process. From a sensory point of view, a lower floral modulation was found when using commercial Enartis Ferm SC Saccharomyces cerevisiae yeasts. In conclusion, it the importance was demonstrated of isolated strains from the region used in fermentation processes, resulting in more aromatic and locally specific red wines. [ABSTRACT FROM AUTHOR]

Background: Psychological anxiety and depression, as well as memory impairment, are frequently linked to inflammation. Clove essential oil (CEO) administration and hydrogen (H2) inhalation have been proven to have anti-inflammatory and alleviating effects on related psychological disorders in the past. The current study investigated the potential to improve anxiety-like behaviors and cognitive function by a combination of CEO and H2 treatment. Methods: The mice were administered lipopolysaccharide (LPS) to induce inflammation and oxidative stress response and cause psychological disorders. Using this animal model, we conducted experiments to test whether essential oil and H2 inhalation could improve the psychological damage in behavior caused by LPS. Subsequently, elevated plus maze (EPM), forced swimming test (FST), and passive avoidance (PA) test were performed for evaluation of mice anxiety, depression, and response to electric shock, respectively. Furthermore, the biochemical analysis was used to examine the expression levels of inflammatory and oxidative stress markers. Results: Our results showed that CEO administration and H2 inhalation alone or in combination positively improved inflammation-induced anxiety, depression, and cognitive memory deficits in the mice. In the single treatment groups, CEO demonstrated better results than H2 inhalation in the elevated plus maze, forced swimming, and passive avoidance tests, while combined treatment with both provided a further improved enhancement effect. Biochemical analysis of the cerebral cortex revealed that CEO and H2 therapy reversed the LPS-induced inflammation and oxidative stress response. Conclusions: Our results suggest that a combination of CEO and H2 has the potential to treat psychological disorders or neuropsychiatric disorders. [ABSTRACT FROM AUTHOR]

Background: Melaleuca species (family Myrtaceae) are characterized by their wide-ranging applications as antimicrobials and in skin-related conditions. Herein, we estimated the volatile profile and biological significance of M. rugulosa (Link) leaves for the first time supported by a dereplication protocol. Materials and methods: Volatile components were extracted using hydrodistillation (HD), supercritical fluid (SF), and headspace (HS) techniques and identified using GC/MS. The variations among the three extracts were assessed using principal component analysis and orthogonal partial least square discriminant analysis (OPLS-DA). The extracted volatiles were tested for radical scavenging activity, anti-aging, and anti-hyperpigmentation potential. Finally, disc diffusion and broth microdilution assays were implemented to explore the antibacterial capacity against Streptococcus pyogenes, Staphylococcus aureus, Clostridium perfringens, and Pseudomonas aeruginosa. Results: The yield of the SF technique (0.8%) was three times higher than HD. GC/MS analysis revealed that the oxygenated compounds are the most proponents in the three extracts being 95.93% (HD), 80.94% (HS), and 48.4% (SF). Moreover, eucalyptol (1,8-cineol) represents the major component in the HD-EO (89.60%) and HS (73.13%) volatiles, while dl-α-tocopherol (16.27%) and α-terpineol (11.89%) represent the highest percentage in SF extract. Regarding the bioactivity profile, the HD-EO and SF-extract showed antioxidant potential in terms of oxygen radical absorbance capacity, and β- carotene assays, while exerting weak activity towards DPPH. In addition, they displayed potent anti-elastase and moderate anti-collagenase activities. The HD-EO exhibited potent anti-tyrosinase activity, while the SF extract showed a moderate level compared to tested controls. OPLS-DA and dereplication studies predicted that the selective antibacterial activity of HD-EO to S. aureus was related to eucalyptol, while SF extract to C. perfringens was related to α-tocopherol. Conclusions: M. rugulosa leaves are considered a vital source of bioactive volatile components that are promoted for controlling skin aging and infection. However, further safety and clinical studies are recommended. [ABSTRACT FROM AUTHOR]

This study is an investigation of the impact of volatile phenols (VPs) released from burning wood during wildfires on grape composition and the resulting wines. Baseline levels of VPs in grapes and sensory differences between smoke-impacted wines and non-smoke-impacted wines were determined. The differences were related to different levels of smoke taint marker compounds in different wine matrices, using modified descriptive analysis (DA), multivariate statistics, gas chromatography mass spectrometry (GC-MS) and liquid chromatography-triple quadrupole tandem mass spectrometry (LC-QqQ-MS) of the free and total VPs, and individual bound glycosides, respectively. Across two DA panels, Cabernet Sauvignon, Cabernet Franc, Petite Verdot, Merlot, Syrah, Malbec, and Zinfandel wines made from grape originating from different areas in California were evaluated. The results show sensory differences between highly smoke-impacted and non-impacted wines with wines made from highly smoke-impacted grapes characterized as smoky, barbeque, medicinal, and having a retro-nasal ashtray character. Low smoke-impact wines based on free and total VP concentrations were not significantly different from the non-impacted wines when rated through descriptive analysis. The amount of smoke exposure was the largest contributor to smoke impact determined by sensory evaluation, but the different wine matrices from different locations and varietals also played an important role in determining the level of perceived smoke impact. The results of this study will contribute to our understanding of smoke impact and how it influences wine characteristics by relating smoke marker indicator compounds to wine sensory attributes. [ABSTRACT FROM AUTHOR]

Background: Achillea fragrantissima (F. Asteraceae) is traditionally used to treat skin infections and inflammation. The present work intended to prepare essential oils (EOs) from A. fragrantissima aerial parts growing widely in Egypt and investigate its antibacterial activity against skin-related pathogens and in vitro cell-based anti-inflammatory activity. Methods: EOs of the fresh aerial parts were extracted by hydrodistillation (HD), microwave-assisted hydrodistillation (MAHD), and head-space (HS), while those of the dried ones were prepared by supercritical fluid (SF). The result EOs were analyzed using GC/MS. The antibacterial activity was evaluated alongside Pseudomonas aeruginosa ATCC 9027, Escherichia coli ATCC 8739, Staphylococcus aureus ATCC 25923, Streptococcus pyogenes ATCC 12344, Clostridium perfringens ATCC 13124 by agar diffusion, microwell dilution, and biofilm formation tests. The anti-inflammatory activity was evaluated by measuring tumor necrosis factor-alpha (TNF-α), interleukin 2 (IL-2), and 6 (IL-6) in lipopolysaccharides (LPS)- stimulated RAW 264.7 cells using ELISA assays in addition, expression of nitric oxide synthase (iNOS) was measured via western blot. Results: The SF method gave the highest EO yield (1.50 mL v/w). Oxygenated components constituted the highest percentage in the four methods, 84.14, 79.21, 73.29 and 33.57% in the HS, HD, MAHD, and SF, respectively. Moreover, variation in the amount of identified compounds was apparent; in HS EO α-thujone (29.37%), artemisia ketone (19.59%), and santolina alcohol (14.66%) are major components, while α-thujone (20.38%) and piperatone (12.09%) were significant in HD. Moreover, (+)-spathulenol (12.22%) and piperatone (10.48%) were significant in MAHD, while piperatone (14.83%) and β-sitosterol (11.07%) were significant in SF EO. HD, MAHD, and SF EOs exhibited susceptibility against P. aeruginosa (IZ = 9–14 mm), E. coli (11–13 mm), and C. perfringens (IZ = 10–14 mm) in agar diffusion assay. MAHD EOs demonstrated potent growth inhibition (MICs = 0.25–2 mg/mL), followed by HD EOs (MICs = 13–52 mg/mL) to all tested microorganisms in well microdilution assay. Also, they exert MBC values equal to or higher than the MICs. Furthermore, SF EOs inhibited the biofilm formation of all tested microorganisms by 65.12—80.84%. Specifically, MAHD and HD EOs efficiently suppress the biofilm of S. pyogenes (77.87%) and P. aeruginosa (60. 29%), respectively. Ultimately, HD and SF EOs showed anti-inflammatory activity by suppressing the TNF-α, IL-2, and IL-6 release and iNOS expression in LPS-stimulated RAW 264.7 macrophages. Conclusion: A. fragrantissima EO is rich in oxygenated volatile compounds with antibacterial and anti-inflammatory activities. It is encouraged as a bioactive agent for adjusting skin infections, though additional studies are essential for their safety in clinical settings. [ABSTRACT FROM AUTHOR]

Malathion is one of the commonly used pesticides in India which is toxic as per the World Health Organization. Its residue has been found in industrial effluent, water streams, and agricultural products. Various analytical methods such as gas chromatography, infrared spectroscopy, and thin‐layer chromatography were used for identifying the concentration of pesticides in aqueous phase. Though gas chromatography is one of the best available techniques in pesticide analysis, it involves higher cost. In this study, simple spectrophotometric methods for identifying the malathion in aqueous phase are experimented and compared using UV visible double beam spectrophotometer. Comparing these two methods will help us to select the most suitable method for specific analytical needs, considering factors such as accuracy, sensitivity, ease of use, and safety. This comparative analysis aids in choosing the best method for reliable and efficient determination of malathion. A regression analysis of Beers–Lambert plots showed a good correlation in the concentration range of 0.5–15 mg/L for the abovementioned two spectrophotometrical methods. The results showed that potassium bromate exhibits rapid, stable color complex and linearity in absorbance versus concentration study when compared with ammonium meta vanadate. [ABSTRACT FROM AUTHOR]

This study assessed the stability of commonly used frying oils submitted to a specific heat treatment. Gas chromatographic analysis (GC-FID) revealed a decrease in the content of polyunsaturated fatty acids (PUFAs) and production of linolelaidic acid (18: 2n-6t). Furthermore, electrospray ionization mass spectrometry (ESI-MS) analysis demonstrated that the triacylglycerol (TAG) content of molecules composed of linoleic acid (L), oleic acid (O), and linolenic acid (Ln) exhibited the greatest decrease during heating. Among the evaluated vegetable oils, soybean oil exhibited the lowest temperature of stability. Conversely, the lowest concentration of trans-fatty acids (TFA) was observed for canola oil. [ABSTRACT FROM AUTHOR]

Hypercrosslinked polymers (HCPs) constructed by the Friedel–Crafts alkylation reaction of aromatic compounds have emerged as a new class of porous materials with unique merit. Herein, a HCP named HCP-TPB was coated onto a capillary column through in situ synthesis. The prepared column exhibited a nonpolar nature, and the column efficiency for n-dodecane was 3003 plates m−1. Moreover, the relative standard deviations of retention time and peak area for six replicate injections of the C3–C6 were lower than 0.1% and 1.5%, respectively. The results of this study showed that it is very promising to utilize HCPs as stationary phases for the separation of C3–C6. [ABSTRACT FROM AUTHOR]

Retention index prediction based on the molecule structure is not often used in practice due to low accuracy, the need to use paid software to calculate molecular descriptors (MD), and the narrow applicability domain of many models. In recent years, relatively accurate and versatile deep learning (DL)‐based models have emerged. These models are now used in practice as an additional criterion in gas chromatography‐mass spectrometry identification. The DB‐225ms stationary phase (usually described as 50%‐cyanopropylphenyl‐50%‐dimethylpolysiloxane in available sources) is widely used, but ready‐to‐use retention index estimation models are not available for it. This study presents such models. The models are linear and use simple constitutional MD and retention indices predicted by DL for the DB‐WAX and DB‐624 stationary phases as MD (we show that it is their use that allows us to achieve satisfactory accuracy). The accuracy obtained for a completely unseen hold‐out test set: root mean square error 73.2; mean absolute error 45.7; median absolute error 22.0. The models were trained using a retention data set of 266 volatile compounds. All calculations can be performed using the convenient open‐source software CHERESHNYA. The final equations are implemented as a spreadsheet and a code snippet and are available online: https://doi.org/10.6084/m9.figshare.26800789. [ABSTRACT FROM AUTHOR]

The persistence of bacterial infections and antibiotic resistance in secondary root canal infections necessitate effective antimicrobial approaches utilizing natural compounds. This study aimed to evaluate the extraction efficiency, phytochemical composition, and antibacterial activity of the ethanol extract of Aceh patchouli leaves (Pogostemon cablin Benth.) against Enterococcus faecalis. The maceration method was employed for extraction and phytochemical analysis was conducted using gas chromatography-mass spectrometry (GC-MS). Antibacterial activity was assessed using the Kirby-Bauer method, and the minimum inhibitory concentration (MIC) was determined using UV-vis spectrophotometry. The results indicated a total extract yield of 17.25% and significant antibacterial activity against E. faecalis. The active compounds in the extract were primarily sesquiterpenes and fatty acids, with patchouli alcohol as the most prominent. The MIC value was 12.5%, suggesting the potential of Aceh patchouli extract as an alternative or adjunctive treatment for root canal infections. This study has the potential to make Aceh's indigenous Pogostemon cablin Benth. plant as an alternative or adjunctive treatment for root canal infections leading to safe and effective treatments that minimize the risk of antibiotic resistance. [ABSTRACT FROM AUTHOR]

The coupling of Solid-Phase Microextraction (SPME) technology with gas chromatography (GC) has a well-established and successful history. Traditionally, SPME fibers have been the most popular form thanks to their versatility and the ease with which they can be fully automated. However, alternative geometries for SPME have been developed over the years, beginning with Stir Bar Sorptive Extraction (SBSE) and later evolving into Thin-Film SPME (TF-SPME) devices. Each of these formats offers distinct advantages and disadvantages, which are explored in this study. The primary objective of this study was to comprehensively compare available forms of SPME devices, with a special focus on the advantages of TF-SPME, a novel microextraction method particularly suited for the analysis of odorants in food. The study involved analyzing a standard mixture of 11 key food odorants, representing a range of polarities, to evaluate the efficiency of TF-SPME devices in terms of the number of analytes extracted. Furthermore, four types of TF-SPME devices were compared against each other in both standard mixtures and actual food samples. The final stage of the study employed GCxGC-ToFMS analysis to showcase the potential of the most efficient HLB-TF-SPME device in the non-targeted analysis of complex samples, exemplified by unfiltered wheat beer. This analysis demonstrated the significant capability of HLB-TF-SPME in capturing and identifying a wide range of volatile compounds in complex matrices. [ABSTRACT FROM AUTHOR]

The study aims to synthesize a selective matrix imprinted sorbent for the extraction of parathion and malathion. The structural unit of the polymeric framework was 2-methylpropanoic acid, the intermolecular crosslinker was ethylene glycol dimethacrylate, the polymerization initiator was azobisisobutyronitrile, the porogen was xylene, and the analyte was parathion. The synthesis was carried out under conditions of heating the reaction mixture to 65 °C, after which the matrix was washed with methanol to remove the analyte. For comparison purposes, non-imprinted control polymer was used as a negative control, which was prepared similarly, but without the addition of the analyte. The identification and quantification of organophosphates were performed by gas chromatography, and the morphological characteristics of the sorbents were evaluated by scanning electron microscopy. The optimal buffer for the purification of organophosphates was acetate buffer with a pH of 4; the optimal organic eluent was methanol. The limit of detection for para- and malathion was 0.1 μg/ml; the limit of quantification was 0.3 μg/ml. Linearity in the extraction conditions was observed in the range of 0.1–1 μg/ml for parathion and 0.1–2 μg/ml for malathion. The developed method will enable quick, selective, and cost-effective extraction of organophosphates from various substrates. [ABSTRACT FROM AUTHOR]

To eliminate the problem of the aging of cellulose insulation in the manufacturing stage, a new drying method is being developed based on the use of methanol vapors. Previous studies have shown that the complete removal of methanol from the cellulose insulation after the drying process is very difficult. Therefore, it is necessary to check how the remaining methanol after drying affects the properties of both the cellulose materials and mineral oil. To conduct such studies, it is necessary to know the methanol content in oil that can be expected depending on its initial content in the cellulose materials and the temperature of the insulation system. Therefore, the main goal of this work is to develop methanol equilibrium curves for oil–paper insulation. To achieve the assumed goal, three-stage studies were conducted. A gas chromatograph equipped with a flame ionization detector was used in all stages of these studies. The gas partition coefficient between oil and air was determined for a temperature of 70 °C. The key experimental finding was the development of methanol equilibrium curves for oil–paper insulation. Thanks to this achievement, it is possible to estimate the methanol content in cellulose materials and mineral oil depending on the insulation temperature. Such data are necessary, among others, to plan appropriate studies aimed at assessing the impact of methanol content on the dielectric and physicochemical properties of these materials, important from the point of view of the operation of power transformers. [ABSTRACT FROM AUTHOR]

Understanding consumers' sensory preferences for dairy products is essential. This study employed sensory analysis and instrumental techniques to analyze the flavor of pasteurized milk and UHT milk. There were 6 milk samples with similar fat content (4.0–4.6 g/100 mL) and protein content (3.2–3.8 g/100 mL). Sensory data from consumer tests was collected using check-all-that-apply (n = 100) and 9-point hedonic preferences. Research showed that Chinese consumers could distinguish the flavor of the 2 types of milk, and UHT milk showed a higher preference score, which may be due to the more pronounced milky flavor and sweet taste of UHT milk. A total of 48 aroma-active compounds were sniffed through 2-dimensional gas chromatography olfactometry time-of-flight MS, among which 11 were determined as key aroma-active compounds. Correlation analysis showed that milky odor, sweetness, and aftertaste-milky were positively correlated with γ-dodecalactone and γ-nonanolactone. Cooked and oxidized taste were positively correlated with 1-octen-3-ol and E-2-octenal. This study is important for developing Chinese dairy products and exporting dairy products to China by multinational companies. The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, two alternative ways of analyzing three‐way data with multivariate curve resolution alternating least squares (MCR‐ALS) using the trilinearity constraint are described and compared. Different synthetic datasets and experimental three‐way datasets covering different scenarios are analyzed, and the results obtained are compared. The two new different ways of applying the trilinearity constraint are named flexible trilinearity alignment (FTA) and shift invariant transformation (SIT). The effects of noise in the application of both types of constraints are investigated in detail. Results show that both approaches are particularly adequate for those cases like in gas chromatography and especially in liquid chromatography where the elution profiles of the same chemical component in different chromatographic runs are not totally reproducible because they are time shifted, although they preserve their shape. When strong time shifts and co‐elution occur, then the "standard" trilinear model does not work, and alternative approaches should be used, such as the MCR extended bilinear model to multiset (multirun) data, or the proposed relaxation of the trilinearity constraint in the FTA and SIT methods to capture the time drift changes produced in the elution profiles of the resolved components. [ABSTRACT FROM AUTHOR]

Cholelithiasis (gallstone disease) is a multifactorial condition characterized by the formation of gallstones. Investigation of the composition of gallstones is essential for understanding the mechanisms of their formation and addressing various practical issues. Currently, it remains unclear which protein components are involved in gallstone formation and how they are related to other components of the stones. This study demonstrates a potential for the qualitative and quantitative determination of amino acids in gallstones of men and women of different ages using gas chromatography (GC-17A chromatograph, Shimadzu, Japan). The analysis of the amino acid composition of gallstones involves the acid hydrolysis of the samples in 6 M HCl at 105°C for 12 h, followed by purification, derivatization of the isolated amino acids, and their determination by gas chromatography. This method allows for the identification of both D- and L-forms of amino acids. A statistical analysis of the obtained data was performed using the STATISTICA 6.0. The study found that cholesterol gallstones in women under the age 50 have the lowest amino acid content. In the amino acid composition of cholesterol gallstones, glycine, along with the L-forms of serine, alanine, and glutamic acid, predominates. Cholesterol gallstones with a mineral component are typical in elderly women (over 60 years old) and middle-aged men (from 37 years old) and exhibit higher amino acid contents than pure cholesterol gallstones. In this type of stones, glycine and the L-forms of leucine, glutamic acid, and aspartic acid predominate. The highest amino acid content was found in pigment stones, both in men and women over the age 55. The amino acid composition of pigment-type stones is dominated by glycine and the L-forms of glutamic acid, aspartic acid, leucine, and alanine. D-amino acids were not detected in cholesterol gallstones. However, D-aspartic acid was found in cholesterol stones with a mineral component and in pigment gallstones. These findings suggest that gas chromatography is a suitable method for studying the amino acid composition of gallstones. [ABSTRACT FROM AUTHOR]

Abraham's solvation parameter model was employed as a Quantitative-Structure Property Relationship in the present study to define safrole descriptor values. Safrole has applications in a wide range of fields, including pharmaceuticals and fragrances, as a flavouring ingredient, a fragrant agent, and a raw material. Safrole, on the other hand, can behave as a toxic organic substance. Safrole descriptor values were calculated using gas-liquid chromatographic retention factors in combination with liquid-liquid partition coefficients. Experimentally determined descriptor values for safrole using gas chromatography and liquid-liquid partition systems are E = 1.108, S = 1.123, A = 0.000, L = 5.340, B = 0.174, and V = 1.246. Proposed descriptor values will be useful in determining and estimating physicochemical properties of Safrole. [ABSTRACT FROM AUTHOR]

In this study, methyl 3-nitrobenzoate, a popular compound used to protect crops and in the textile industry, was studied using liquid–liquid partitioning and gas chromatography and the Abraham solvation parameter descriptor values were determined for potential applications in QSPR. The solver algorithm in Excel was used to determine the descriptor values for methyl 3-nitrobenzoate, resulting in E = 1.0616, S = 1.4170, A = 0.00, L = 6.1354, B = 0.6198, and V = 1.2468 with a standard deviation of 0.076. In the situations when toxicity and exposure assessment data are scarce, the application of QSPR models, such as the Abraham solvation parameter model, can aid in the estimation of the environmental impact of chemicals. With the objective to facilitate physicochemical property estimations of methyl 3-nitrobenzoate widely used in the textile and agricultural industries, this study offers experimental solute descriptor values of the Abrham's solvation parameter model. [ABSTRACT FROM AUTHOR]