Humans interact with thousands of chemicals. This study aims to identify substances of emerging concern and in need of human health risk evaluations. Sixteen pooled human serum samples were ...constructed from 25 individual samples each from the National Institute of Environmental Health Sciences’ Clinical Research Unit. Samples were analyzed using gas chromatography (GC) × GC/time-of-flight (TOF)-mass spectrometry (MS) in a suspect screening analysis, with follow-up confirmation analysis of 19 substances. A standard reference material blood sample was also analyzed through the confirmation process for comparison. The pools were stratified by sex (female and male) and by age (≤45 and >45). Publicly available information on potential exposure sources was aggregated to annotate presence in serum as either endogenous, food/nutrient, drug, commerce, or contaminant. Of the 544 unique substances tentatively identified by spectral matching, 472 were identified in females, while only 271 were identified in males. Surprisingly, 273 of the identified substances were found only in females. It is known that behavior and near-field environments can drive exposures, and this work demonstrates the existence of exposure sources uniquely relevant to females.
Microplastics are of major concerns for society and is currently in the focus of legislators and administrations. A small number of measures to reduce or remove primary sources of microplastics to ...the environment are currently coming into effect. At the moment, they have not yet tackled important topics such as food safety. However, recent developments such as the 2018 bill in California are requesting the analysis of microplastics in drinking water by standardized operational protocols. Administrations and analytical labs are facing an emerging field of methods for sampling, extraction, and analysis of microplastics, which complicate the establishment of standardized operational protocols. In this review, the state of the currently applied identification and quantification tools for microplastics are evaluated providing a harmonized guideline for future standardized operational protocols to cover these types of bills. The main focus is on the naked eye detection, general optical microscopy, the application of dye staining, flow cytometry, Fourier transform infrared spectroscopy (FT-Ir) and microscopy, Raman spectroscopy and microscopy, thermal degradation by pyrolysis–gas chromatography–mass spectrometry (py-GC-MS) as well as thermo-extraction and desorption gas chromatography–mass spectrometry (TED-GC-MS). Additional techniques are highlighted as well as the combined application of the analytical techniques suggested. An outlook is given on the emerging aspect of nanoplastic analysis. In all cases, the methods were screened for limitations, field work abilities and, if possible, estimated costs and summarized into a recommendation for a workflow covering the demands of society, legislation, and administration in cost efficient but still detailed manner.
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•Aromas in CWO and HWO was compared by GC × GC-O-MS and HS-GC-IMS.•Allyl isothiocyanate and 6-methyl-5-hepten-2-one were identified firstly in WO.•76 and 123 compounds were sniffed in ...CWO and HWO by GC × GC-O-MS.•The flavor of CWO and HWO was reconstructed and restored.
Aroma composition of cold-pressed walnut oil (CWO) and hot-pressed walnut oil (HWO) was analyzed by comprehensive two-dimensional gas chromatography-olfactory-mass spectrometry (GC × GC-O-MS) and headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS). A total of 83 and 197 compounds were identified in the CWO and HWO, respectively; among these, 76 and 123 compounds were sniffed exclusively by GC × GC-O-MS, respectively. A total of 36 volatile compounds were detected by HS-GC-IMS, of which 10 in CWO and 32 in HWO. Based on of flavor dilution (FD) factors, odor-activity values (OAVs), and recombination and omission experiments, 1-octen-3-ol, cyclohexanol, and benzaldehyde were found to be the key aroma-active compounds in CWO, while 3-methylbutanal, (E,E)-2,4-nonadienal, nonanal, 1-octen-3-ol, 3-pentanol, 1-octanol, and furfural were the key aroma-active compounds in HWO. Moreover, Maillard reaction and lipid oxidation were found to play an important role in flavor formation in HWO. This study provides a guide to improve the quality of walnut oil based on aroma characteristics.
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•Hardwood and softwood were submitted to intermediate, fast and catalytic pyrolysis.•Major compounds were phenols & ketones for IP & FP and hydrocarbons for the CFP.•GC×GC/TOFMS as a ...technique of choice to avoid co-elutions of wood biomarkers and PAH.•Especial attention was given to observe toxic compounds formed during the CFP.•Possible biomarkers (dimethoxy-phenols) for the wood bio-oils are proposed.
Bio-oils were produced through intermediate (IP) and fast pyrolysis (FP), using Eucalyptus sp. (hardwood) and Picea abies (softwood), wood wastes produced in large scale in Pulp and Paper industries. Characterization of these bio-oils was made using GC/qMS and GC×GC/TOFMS. The use of GC×GC provided a broader characterization of bio-oils and it allowed tracing potential markers of hardwood bio-oil, such as dimethoxy-phenols, which might co-elute in 1D-GC. Catalytic FP increased the percentage of aromatic hydrocarbons in P. abies bio-oil, indicating its potential for fuel production. However, the presence of polyaromatic hydrocarbons (PAH) draws attention to the need of a proper management of pyrolysis process in order to avoid the production of toxic compounds and also to the importance of GC×GC/TOFMS use to avoid co-elutions and consequent inaccuracies related to identification and quantification associated with GC/qMS. Ketones and phenols were the major bio-oil compounds and they might be applied to polymer production.
Pesticides can be found in beehives for several reasons, including contamination from surrounding crops or for their use by beekeepers, which poses a risk to bee ecosystems and consumers. Therefore, ...efficient and sensitive methods are needed for determining pesticide residues in bee products. In this study, a new analytical method has been developed and validated to determine seven acaricides (atrazine, chlorpyrifos, chlorfenvinphos, α-endosulfan, bromopropylate, coumaphos, and τ-fluvalinate) in bee pollen using gas chromatography coupled to mass spectrometry. After an optimization study, the best sample treatment was obtained when using a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method employing an ethyl acetate and cyclohexane as the extractant mixture, and a mixture of salts for the clean-up step. A chromatographic analysis (<21 min) was performed in an Agilent DB-5MS column, and it was operated under programmed temperature conditions. The method was fully validated in terms of selectivity, limits of detection (0.2-3.1 µg kg
) and quantification (0.6-9.7 µg kg
), linearity, matrix effect (<20% in all cases), trueness (recoveries between 80% and 108%), and precision. Finally, the proposed method was applied to analyze commercial bee pollen samples, and some of the target pesticides (chlorfenvinphos, α-endosulfan, coumaphos, and τ-fluvalinate) were detected.
Aims
This study sought to assess the volatile organic compound (VOC) profiles of ampicillin‐resistant and ‐susceptible Escherichia coli to evaluate whether VOC analysis may be utilized to identify ...resistant phenotypes.
Methods and Results
An E. coli BL21 (DE3) strain and its pET16b plasmid transformed ampicillin‐resistant counterpart were cultured for 6 h in drug‐free, low‐ and high‐concentrations of ampicillin. Headspace analysis was undertaken using thermal desorption‐gas chromatography‐mass spectrometry. Results revealed distinct VOC profiles with ampicillin‐resistant bacteria distinguishable from their susceptible counterparts using as few as six compounds. A minimum of 30 compounds (fold change >2, p ≤ 0.05) were differentially expressed between the strains across all set‐ups. Furthermore, three compounds (indole, acetoin and 3‐methyl‐1‐butanol) were observed to be significantly more abundant (fold change >2, p ≤ 0.05) in the resistant strain compared to the susceptible strain both in the presence and in the absence of drug stress.
Conclusions
Results indicate that E. coli with acquired ampicillin resistance exhibit an altered VOC profile compared to their susceptible counterpart both in the presence and in the absence of antibiotic stress. This suggests that there are fundamental differences between the metabolisms of ampicillin‐resistant and ‐susceptible E. coli which may be detected by means of VOC analysis.
Significance and Impact of the Study
Our findings suggest that VOC profiles may be utilized to differentiate between resistant and susceptible bacteria using just six compounds. Consequently, the development of machine‐learning models using VOC signatures shows considerable diagnostic applicability for the rapid and accurate detection of antimicrobial resistance.
A low solvent consumption method was developed to determine 27 different classes of pesticides (including organochlorine pesticide, organophosphorus pesticide, pyrethroid pesticide, fungicide, ...herbicide and acaricide) in wine using dispersive liquid–liquid microextraction (DLLME). Extraction parameters including type and volume of extraction solvent, type and volume of disperser solvent, salinity, pH, centrifugation time, vortex extraction time and wine volumes were optimized. A mixture of 60μL chloroform (extraction solvent) and 940μL acetonitrile (disperser solvent) was injected into 5mL wine diluent. After shaking and centrifugation, the sedimented phase was transferred into a 200μL glass insert and determined by gas chromatography–mass spectrometry method (GC–MS). The results demonstrated that the recoveries for all the pesticides spiked at three different levels ranged from 66.7 to 126.1%. The intra-day repeatabilities (RSDs) ranged from 2.0 to 27.2%. The limits of detection ranged from 0.025 to 0.88μg/L, and the limits of quantification ranged from 0.082 to 2.94μg/L. The proposed method is very low cost, rapid and convenient, and could be an effective method for monitoring of multi-pesticide in wine.
•A sensitive DLLME method was developed to determine 27 pesticides in wine.•The method covered different classes of pesticides in one analysis.•The method was low cost, rapid and convenient.
Persistent organic pollutants (POPs) are harmful to the environment and human health. A simple method was developed for the determination of 58 POPs, including 16 polycyclic aromatic hydrocarbons ...(PAHs), 18 polychlorinated biphenyls (PCBs), and 24 organochlorine pesticides (OCPs), in atmospheric gaseous and particle-phase samples. Different extraction solvents, solid-phase extraction (SPE) cartridges and elution steps were used and compared to optimize the extraction efficiency. The POPs were isolated from the atmospheric samples by Soxhlet extraction using 1:1 acetone:n-hexane and separated using SPE cartridges. The fractions were collected by two-step elution with10 mL of n-hexane and 10 mL of 1:1 n-hexane:dichloromethane. The method validation showed that PAHs, PCBs and OCPs had good linearity, with the coefficients of determination higher than 0.995, from 2.5 to 800, 2.5 to 800, and 2.5 to 600 ng/mL, respectively. The average recoveries were 67-117%, 67-113%, and 73-114% for the PAHs, PCBs, and OCPs. The limits of detection for PAHs, PCBs, and OCPs were from 0.55 to 3.29, 0.09 to 2.00, and 0.57 to 4.86 pg/m
3
. The limits of quantification (LOQs) for PAHs, PCBs and OCPs were 1.80 to 10.48, 0.29 to 6.37, and 1.82 to 15.48 pg/m
3
. The applicability of the method was confirmed using an urban dust standard reference material. The method was employed for the analysis of atmospheric samples collected weekly for one-half year on the rooftop of a 14 m tall building in the downtown Mianyang, Sichuan, China. The developed method is demonstrated to accurately monitor persistent organic pollutants in the atmosphere.
Effect of storage on metabolites of brown rice Wang, Changyuan; Feng, Yuchao; Fu, Tianxin ...
Journal of the science of food and agriculture,
September 2020, 2020-Sep, 2020-09-00, 20200901, Volume:
100, Issue:
12
Journal Article
Peer reviewed
Background
Storage is an essential part of brown rice circulation. During the storage process, the metabolic activity of brown rice is still ongoing, and long‐term storage leads to the deterioration ...of brown rice. Metabolomics analysis was performed using gas chromatography–mass spectrometry to investigate the changes in metabolites of brown rice after storage at 18 °C for 12 months.
Results
In terms of quantity, sugar, fatty acids, and other metabolites in brown rice decreased after storage, and alcohols, aldehydes, phenols, and amines increased. A total of 34 differential metabolites were screened. In terms of contents, carbohydrates, amino acids, and fatty acids of brown rice decreased after storage, while those of sugar alcohol, amines, and aldehydes increased after storage. Cluster analysis of the samples at zero storage time revealed that the metabolites expressed least became highly expressed after storage and those expressed highly became low after storage. Metabolic pathway analysis showed that storage significantly influenced the lipid metabolism in brown rice. Palmitoleic acid, cholesterol, linoleic acid, and lauric acid are four key metabolites in lipid metabolism during storage of brown rice.
Conclusion
Significant changes occurred in quantity and type of brown rice metabolites after storage. Storage has the greatest effect on lipids. Storage caused a ‘reverse change’ in the metabolites content of brown rice. The results obtained may help in understanding the changes in metabolites profile and delaying of the quality deterioration of brown rice during storage.
In this study, the flavor compounds of Camellia seed oils obtained by four processes were characterized by headspace solid phase microextraction/gas chromatography/mass spectrometry (HS-SPME/GC/MS). ...A variety of about 76 volatile flavor compounds were identified from all the oil samples. Of the four processing processes, the pressing process can retain a lot of volatile components. Among these, compounds nonanal and 2-undecenal were predominantly in the majority of the samples. Meanwhile, other compounds such as octyl ester formic acid, octanal and 2-nonenal (E), 3-acetyldihydro 2(3H)-furanone, (E)-2-decenal, dihydro-5-penty 2(3H)-furanone, nonanoic acid, and dodecane were also among the most consistently found compounds among the oil samples analyzed. The principal component analysis carried out to categorize the data produced seven clusters of the total oil samples based on the number of flavor compounds obtained in each sample. This categorization would lead to understanding the components which highly contributed to the characteristic volatile flavor and build up the flavor profile of Camellia seed oil.
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