Ultrahigh Resolution Mass Spectrometry Research Articles

Molecular and physical composition of tar balls in wildfire smoke: an investigation with complementary ionisation methods and 15-Tesla FT-ICR mass spectrometry

Laser desorption ionisation, coupled with ultrahigh-resolution mass spectrometry, provides an apt reflection of the physical properties of tar balls in wildfire smoke.

An Integrative Pharmacology-Based Strategy to Uncover the Mechanism of Zuogui Jiangtang Shuxin Formula in Diabetic Cardiomyopathy.

This study aimed to explore the mechanism of Zuogui Jiangtang Shuxin formula (ZGJTSXF) in the treatment of diabetic cardiomyopathy (DCM) by an integrative strategy combining serum pharmacochemistry, network pharmacology analysis, and experimental validation. An Ultra high performance liquid chromatography-high resolution mass spectrometry (UPLC-Q-Exactive-Orbitrap-MS) method was constructed to identify compounds in rat serum after oral administration of ZGJTSXF. A component-target network between the targets of ZGJTSXF ingredients and DCM was established using Cytoscape. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed to deduce ZGJTSXF-associated targets and pathways. The DCM model mice were treated with ZGJTSXF, and the predicted important signaling pathways were verified using quantitative PCR and Western blot. We identified 78 compounds in serum of medicated rats, which mainly included flavonoids, small peptides, nucleosides, organic acids, phenylpropanoids, alkaloids, phenanthrenequinones, iridoids, phenols, and saponins. Network pharmacology analysis revealed that ZGJTSXF may regulate targets including ALB, TNF, AKT1, GAPDH, VEGFA, EGFR, SRC, CASP3, MAPK3, JUN, and PI3K/AKT signaling pathway in the treatment of DCM. ZGJTSXF administration improved blood sugar levels, heart function, and cardiac morphological changes in DCM mice. Notably, ZGJTSXF inhibited cardiomyocytes apoptosis, which was associated with restored PI3K/Akt signaling and upregulated Bcl-2 and Bcl-xL proteins expression. Our preliminary results proposed the material basis and possible mechanisms of ZGJTSXF in treating DCM, which is related to the activation of the PI3K/AKT signaling pathway and apoptosis inhibition. These findings shed new light in developing ZGJTSXF-based therapeutics in treating DCM.

Quantification and isotope abundance determination of 13C labeled intracellular sugar metabolites with hydrophilic interaction liquid chromatography.

Metabolic flux analysis (MFA) using stable isotope labeled tracers is a powerful tool to estimate fluxes through metabolic pathways. It finds applications in studying metabolic changes in diseases, regulation of cellular energetics, and novel strategies for metabolic engineering. Accurate and precise quantification of the concentration of metabolites and their labeling states is critical for correct MFA results. Utilizing an ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS) system, an analytical method for simultaneously quantifying the concentration of sugar metabolites and their mass isotopologue distribution (MID) was developed. The method performs with good linearity and coefficient of determination (R2) > 0.99, while the detection limit ranged from 0.1 to 50 mg L-1. Seven sugar metabolites were detected in a labeled Brevibacterium flavum sample using the method. The detected quantities ranged from 6.15 to 3704.21 mg L-1, and 13C abundance was between 12.77% and 66.67% in the fermentation fluid and 16.28% and 91.93% in the bacterial body. Overall, the method is efficient, accurate, and suitable for analysis of labeled sugar metabolites in 13C MFA studies.

Molecular compositions and optical properties of water-soluble brown carbon during the autumn and winter in Guangzhou, China

Brown carbon (BrC) has attracted increasing attention due to its significant effects on the atmospheric environment and climate. In this study, we investigated the seasonal variations of the optical and molecular properties of water-soluble BrC in Guangzhou and the key factors affecting its light absorption and fluorescence properties. The mass absorption efficiency at 365 nm (MAE365) indicated that water-soluble BrC had a stronger light absorption capacity in winter than in autumn. An excitation emission matrix-parallel factor analysis (EEM-PARAFAC) identified four fluorescent components (C1–C4) in the water-soluble organic compound (WSOC) fraction, of which the humic-like components (C1, C2, and C4) were the dominant fluorophores. More C1 and C4 components were detected in autumn WSOC, whereas more C3 component in winter WSOC, which was mainly due to the differences in the sources and oxidation processes of WSOC in different seasons. The molecular composition of WSOC also indicated significant seasonal variations as revealed by an electrospray ionization ultrahigh-resolution mass spectrometry (ESI-UHRMS) analysis. The autumn WSOC had a higher degree of oxidation, whereas the winter WSOC had a higher aromaticity. Furthermore, a principal component analysis (PCA) and the Pearson correlation coefficients indicated that the light absorption of water-soluble BrC over Guangzhou was mainly affected by their aromaticity and N-containing species, with aromatic CHO and CHON compounds being the most important chromophores. The fluorescent components C1 and C4 were characterized by a relatively high oxidation level, which may be more relevant to aged organic aerosols with a high aromaticity and oxidation. The fluorescent component C3 may be more relevant to the primary emission of organic aerosols or fresh organic aerosols with low oxidation, and some non-nitrogen-containing species also had associations with previously assigned protein-like components (C3).

Pharmacokinetics of a long-acting subcutaneous eprinomectin injection in semi-domesticated reindeer (Rangifer tarandus tarandus) – A pilot study

Reindeer (Rangifer tarandus tarandus) are exposed to the pathogenic parasitic nematode Elaphostrongylus rangiferi during grazing. The severity of disease is dose-dependent. Prophylactic anthelmintic treatment is needed to improve animal health and reindeer herding sustainability. Herds are traditionally only gathered once during the summer, requiring a drug with a persistent effect. In this study we investigated the suitability of long-acting eprinomectin, given as a single subcutaneous injection at 1 mg/kg bodyweight in adult reindeer and calves. Plasma and faeces concentrations were determined using ultra-high performance liquid chromatography high resolution mass spectrometry (UHPLC-HRMS). Plasma concentrations remained above the presumed effect level of 2 ng/mL for 80 days, demonstrating the drug’s potential. Pharmacokinetic parameters were compared to other species using allometric scaling. Calves and adults had slightly different profiles. No viable faecal nematode eggs were detected during treatment. Eprinomectin was measurable in the reindeer faeces up to 100 days, which is of environmental concern.

Rainstorms drive export of aromatic and concurrent bio-labile organic matter to a large eutrophic lake and its major tributaries

Lakes are hotspots for global carbon cycling, yet few studies have explored how rainstorms alter the flux, composition, and bio-lability of dissolved organic matter (DOM) in inflowing rivers using high-frequency monitoring. We conducted extensive campaigns in the watershed of Lake Taihu and made daily observations for three years in its two largest inflowing tributaries, River Dapu and River Yincun. We found higher DOC, bio-labile DOC (BDOC), and specific UV absorbance (SUVA254) levels in the northwestern inflowing regions compared with the remaining lake regions. DOC and BDOC increased during rainstorms in River Dapu, and DOC declined due to local dilution and BDOC increased during rainstorms in River Yincun. We found that rainstorms resulted in increased DOM absorbance a350, SUVA254, and humification index (HIX) and enhanced percentages of humic-like fluorescent components, %polycyclic condensed aromatic and %polyphenolic compounds as revealed from ultrahigh-resolution mass spectrometry (FT-ICR MS), while spectral slope (S275-295) and the percentages of protein-like C1 and C3 declined during rainstorms compared with other seasons. This can be explained by a combined flushing of catchment soil organic matter and household effluents. The annual inflows of DOC and BDOC to Lake Taihu were 1.15 ± 0.18 × 104 t C yr−1 and 0.23 ± 0.06 × 104 t C yr−1 from River Dapu and 2.92 ± 0.42 × 103 t C yr−1 and 0.53 ± 0.07 × 103 t C yr−1 from River Yincun, respectively, and the fluxes of DOC and BDOC from both rivers increased during rainstorms. We found an elevated frequency of heavy rainfall and rainstorms in the lake watershed during the past six decades. We conclude that an elevated input of terrestrial organic-rich DOM with concurrent high aromaticity and high bio-lability from inflowing rivers is likely to occur in a future wetter climate.

Exploratory Metabolomics Underscores the Folate Enzyme ALDH1L1 as a Regulator of Glycine and Methylation Reactions.

Folate (vitamin B9) is involved in one-carbon transfer reactions and plays a significant role in nucleic acid synthesis and control of cellular proliferation, among other key cellular processes. It is now recognized that the role of folates in different stages of carcinogenesis is complex, and more research is needed to understand how folate reactions become dysregulated in cancers and the metabolic consequences that occur as a result. ALDH1L1 (cytosolic 10-formyltetrahydrofolate dehydrogenase), an enzyme of folate metabolism expressed in many tissues, is ubiquitously downregulated in cancers and is not expressed in cancer cell lines. The RT4 cell line (derived from papillary bladder cancer) which expresses high levels of ALDH1L1 represents an exception, providing an opportunity to explore the metabolic consequences of the loss of this enzyme. We have downregulated this protein in RT4 cells (shRNA driven knockdown or CRISPR driven knockout) and compared metabolomes of ALDH1L1-expressing and -deficient cells to determine if metabolic changes linked to the loss of this enzyme might provide proliferative and/or survival advantages for cancer cells. In this study, cell extracts were analyzed using Ultra High Performance Liquid Chromatography High Resolution Mass Spectrometry (UHPLC-HR-MS). A total of 13,339 signals were identified or annotated using an in-house library and public databases. Supervised and unsupervised multivariate analysis revealed metabolic differences between RT4 cells and ALDH1L1-deficient clones. Glycine (8-fold decrease) and metabolites derived from S-adenosylmethionine utilizing pathways were significantly decreased in the ALDH1L1-deficient clones, compared with RT4 cells. Other changes linked to ALDH1L1 downregulation include decreased levels of amino acids, Krebs cycle intermediates, and ribose-5-phosphate, and increased nicotinic acid. While the ALDH1L1-catalyzed reaction is directly linked to glycine biosynthesis and methyl group flux, its overall effect on cellular metabolism extends beyond immediate metabolic pathways controlled by this enzyme.

Identification and analysis of the degradation products of chlorothalonil in vegetables

In this study, the untargeted screening of the degradation products of chlorothalonil (CHT) in vegetables was performed using ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS). Sulfhydryl-CHT (SH-CHT) and hydroxyl CHT (OH-CHT) were screened as the key degradation products of CHT in vegetables. SH-CHT is a new degradation product of CHT in the vegetables. This study was the first discover the SH-substituted degradation product of pesticide in vegetables. The chemical structure of SH-CHT was deduced and confirmed through synthetic reference. An efficient method for the simultaneous monitoring of SH-CHT and hydroxyl CHT (OH-CHT) in vegetables has been proposed based on QuEChERS in combination with HPLC-MS/MS analysis. The recoveries of SH-CHT and OH-CHT were in range of 85.8%–105.1% with intra- and inter–relative standard deviation (RSD) of less than 10.0%. The limits of detection were 2.0 μg/kg for SH-CHT and 0.2 μg/kg for OHCHT. Seven kinds of vegetables covering various plant families were processed with CHT. As a result, SH-CHT was detected in five kinds of sulfur-rich vegetables with transformation rates of 7.6%–26.6%. OH-CHT was detected in all the vegetables with transformation rates of 1.7%–14.0%. Toxicity evaluation based on ECOSAR program indicated that SH-CHT had potentially high toxicity to aquatic organisms. This study provides a powerful approach for the monitoring and risk assessment of SH-CHT and OH-CHT in food safety control. Furthermore, the study inspires comprehensive research on the overlooked degradation pathways of pesticides in sulfur-rich vegetables.

Large-Scale Interlaboratory DI-FT-ICR MS Comparability Study Employing Various Systems.

Ultrahigh resolution mass spectrometry (UHR-MS) coupled with direct infusion (DI) electrospray ionization offers a fast solution for accurate untargeted profiling. Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometers have been shown to produce a wealth of insights into complex chemical systems because they enable unambiguous molecular formula assignment even if the vast majority of signals is of unknown identity. Interlaboratory comparisons are required to apply this type of instrumentation in quality control (for food industry or pharmaceuticals), large-scale environmental studies, or clinical diagnostics. Extended comparisons employing different FT-ICR MS instruments with qualitative direct infusion analysis are scarce since the majority of detected compounds cannot be quantified. The extent to which observations can be reproduced by different laboratories remains unknown. We set up a preliminary study which encompassed a set of 17 laboratories around the globe, diverse in instrumental characteristics and applications, to analyze the same sets of extracts from commercially available standard human blood plasma and Standard Reference Material (SRM) for blood plasma (SRM1950), which were delivered at different dilutions or spiked with different concentrations of pesticides. The aim of this study was to assess the extent to which the outputs of differently tuned FT-ICR mass spectrometers, with different technical specifications, are comparable for setting the frames of a future DI-FT-ICR MS ring trial. We concluded that a cluster of five laboratories, with diverse instrumental characteristics, showed comparable and representative performance across all experiments, setting a reference to be used in a future ring trial on blood plasma.

Experimental Insight into the Enigmatic Persistence of Marine Refractory Dissolved Organic Matter.

More than 90% of marine dissolved organic matter (DOM) is biologically recalcitrant. This recalcitrance has been attributed to intrinsically refractory molecules or to low concentrations of molecules, but their relative contributions are a long-standing debate. Characterizing the molecular composition of marine DOM and its bioavailability is critical for understanding this uncertainty. Here, using different sorbents, DOM was solid-phase extracted from coastal, epipelagic, and deep-sea water samples for molecular characterization and was subjected to a 180-day incubation. 1H nuclear magnetic resonance spectroscopy and ultra-high-resolution mass spectrometry (UHRMS) analyses revealed that all of the DOM extracts contained refractory carboxyl-rich alicyclic molecules, accompanied with minor bio-labile components, for example, carbohydrates. Furthermore, dissolved organic carbon concentration analysis showed that a considerable fraction of the extracted DOM (86-95%) amended in the three seawater samples resisted microbial decomposition throughout the 180-day heterotrophic incubation, even when concentrated threefold. UHRMS analysis revealed that DOM composition remained mostly invariant in the 180-day deep-sea incubations. These results underlined that the dilution and intrinsic recalcitrance hypotheses are not mutually exclusive in explaining the recalcitrance of oceanic DOM, and that the intrinsically refractory DOM likely has a relatively high contribution to the solid-phase extractable DOM in the ocean.

Production and Characterization of a Novel Exopolysaccharide from Ramlibacter tataouinensis.

The current study examines the desiccation-resistant Ramlibacter tataouinensis TTB310T as a model organism for the production of novel exopolysaccharides and their structural features. This bacterium is able to produce dividing forms of cysts which synthesize cell-bound exopolysaccharide. Initial experiments were conducted on the enrichment of cyst biomass for exopolysaccharide production under batch-fed conditions in a pilot-scale bioreactor, with lactate as the source of carbon and energy. The optimized medium produced significant quantities of exopolysaccharide in a single growth phase, since the production of exopolysaccharide took place during the division of the cysts. The exopolysaccharide layer was extracted from the cysts using a modified trichloroacetic acid method. The biochemical characterization of purified exopolysaccharide was performed by gas chromatography, ultrahigh-resolution mass spectrometry, nuclear magnetic resonance, and Fourier-transform infrared spectrometry. The repeating unit of exopolysaccharide was a decasaccharide consisting of ribose, glucose, rhamnose, galactose, mannose, and glucuronic acid with the ratio 3:2:2:1:1:1, and additional substituents such as acetyl, succinyl, and methyl moieties were also observed as a part of the exopolysaccharide structure. This study contributes to a fundamental understanding of the novel structural features of exopolysaccharide from a dividing form of cysts, and, further, results can be used to study its rheological properties for various industrial applications.

Quantitating α-amidated peptide degradation by separative technologies and ultra-high resolution mass spectrometry

α-amidation of peptides is a C-terminal modification allowing to improve half-life of therapeutic peptides. However, due to storage conditions, this C-terminal amide function can be partially hydrolyzed into a carboxylic acid moiety, resulting in a decrease of the molecule bioactivity. It is therefore necessary to be able to detect and quantify any trace of this degradation product when dealing with such class of peptides. For this purpose, LC-UV, CE-UV, LC/MS and LC/MS/MS are conventional analytical technologies used in pharmaceutical laboratories to monitor peptide integrity. Since the production of the carboxylated peptide issued from the amidated starting compound is scrutinized, ultra-high-resolution mass spectrometry was investigated without the recourse to any separative method (direct infusion mode) to achieve rapid straightforward relative quantitative analyses from the detected isotopic clusters of both peptides. Indeed, low or high-resolution MS instruments present in pharmaceutical laboratories (fitted with Q, IT or ToF mass analyzers) allow to distinguish both molecular ions that differ from 0.984 Da (NH2 formally substituted by OH). However, the analytical difficulty comes from the fact that the A+1 ion (13C contribution) of the amidated peptide and the A ion (12C contribution) of any produced carboxylated sequence are overlapping hampering the detection of minute amount of the hydrolyzed product. Actually, to differentiate these two isobaric ions, mass analyzers should possess at least a resolution of 90 000 for 7 residues peptides (molecular ions around 700–800 Da) which is presumably attainable with any FT-MS instrument. With an ultra-high-resolution mass spectrometer (FT-ICR MS) the observed fine isotopic structure displaying all expected isotopologues permitted in a single fast analysis to unambiguously detect both compounds (non-hydrolyzed and hydrolyzed one) and subsequently define the relative amount of the carboxylated peptide contaminant. Finally, these results were confronted with conventional measurements recorded with orthogonal methodologies such as LC-UV and CE-UV. The pro and cons of all quantitative strategies are discussed.

Proteomics-Compatible Fourier Transform Isotopic Ratio Mass Spectrometry of Polypeptides

Measuring the relative abundances of heavy stable isotopes of the elements C, H, N, and O in proteins is of interest in environmental science, archeology, zoology, medicine, and other fields. The isotopic abundance measurements of the fine structure of immonium ions with ultrahigh resolution mass spectrometry obtained in gas-phase fragmentation of polypeptides have previously uncovered anomalous deuterium enrichment in (hydroxy)proline of bone collagen in marine mammals. Here, we provide a detailed description and validation of this approach and demonstrate per mil-range precision of isotopic ratio measurements in aliphatic residues from proteins and cell lysates. The analysis consists of proteomics-type experiment demanding sub-microgram amounts of a protein sample and providing concomitantly protein sequence data allowing one to verify sample purity and establish its identity. A novel software tool protein amino acid-resolved isotopic ratio mass spectrometry (PAIR-MS) is presented for extracting isotopic ratio data from the raw data files acquired on an Orbitrap mass spectrometer.

Double-bond equivalence linear equations for structural interpretation of fossil hydrocarbons

The structural elucidation of hydrocarbons still remains a challenge for petroleomics characterization using ultrahigh-resolution mass spectrometry (UHRMS). Double-bond equivalence (DBE) linear equations were proposed for better predicting and understanding the molecular structure of hydrocarbons in crude oils. They were defined as the linear equation in the Cartesian coordinate system with carbon number as the abscissa and DBE as the ordinate, where y-intercepts represented the starting core structures and slopes described the structural increments. According to the magnitude of the slope determined by ΔDBE/ΔC (carbon number), DBE linear equations were divided into three types: alkyl homologous equation, naphthenic homologous equation, and aromatic homologous equation. Any structure of fossil hydrocarbons can be represented by the combination of these three types of equations, as all typical types of structural increments and their adding modes were considered. Furthermore, a distribution map of aromatic hydrocarbons was constructed based on DBE linear equations, which could provide an intuitionistic illustration of the ring structures, especially the aromatic structures of fossil hydrocarbons. The feasibilities of the distribution map to distinguish naphthenic and aromatic rings and to classify the numbers of aromatic rings were verified by experimental results obtained by on-line coupling of normal phase liquid chromatography and ultrahigh-resolution mass spectrometry. In real sample analysis, combination of DBE linear equations and tandem MS was demonstrated to be a superior way for structural elucidation, because DBE linear equations could provide a confined database for effective structural search.

Genome-wide association mapping reveals genes underlying population-level metabolome diversity in a fungal crop pathogen

BackgroundFungi produce a wide range of specialized metabolites (SMs) involved in biotic interactions. Pathways for the production of SMs are often encoded in clusters of tightly arranged genes identified as biosynthetic gene clusters. Such gene clusters can undergo horizontal gene transfers between species and rapid evolutionary change within species. The acquisition, rearrangement, and deletion of gene clusters can generate significant metabolome diversity. However, the genetic basis underlying variation in SM production remains poorly understood.ResultsHere, we analyzed the metabolite production of a large population of the fungal pathogen of wheat, Zymoseptoria tritici. The pathogen causes major yield losses and shows variation in gene clusters. We performed untargeted ultra-high performance liquid chromatography-high resolution mass spectrometry to profile the metabolite diversity among 102 isolates of the same species. We found substantial variation in the abundance of the detected metabolites among isolates. Integrating whole-genome sequencing data, we performed metabolite genome-wide association mapping to identify loci underlying variation in metabolite production (i.e., metabolite-GWAS). We found that significantly associated SNPs reside mostly in coding and gene regulatory regions. Associated genes encode mainly transport and catalytic activities. The metabolite-GWAS identified also a polymorphism in the 3′UTR region of a virulence gene related to metabolite production and showing expression variation.ConclusionsTaken together, our study provides a significant resource to unravel polymorphism underlying metabolome diversity within a species. Integrating metabolome screens should be feasible for a range of different plant pathogens and help prioritize molecular studies.

Detection of Polycyclic Aromatic Hydrocarbons in High Organic Carbon Ultrafine Particle Extracts by Electrospray Ionization Ultrahigh-Resolution Mass Spectrometry.

The detection of polycyclic aromatic hydrocarbons (PAHs) by electrospray ionization (ESI) without additional reagents or targeted setup changes to the ionization source was observed in ultrafine particle (UFP) extracts, with high organic carbon (OC) concentrations, generated by a combustion aerosol standard (CAST) soot generator. Particulate matter (PM) was collected on filters, extracted with methanol, and analyzed by ESI Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Next to oxygen-containing species, pure hydrocarbons were found to be one of the most abundant compound classes, detected as [M + Na]+ or [M + H]+ in ESI+ and mostly as [M - H]- in ESI-. The assigned hydrocarbon elemental compositions are identified as PAHs due to their high aromaticity index (AI > 0.67) and were additionally confirmed by MS/MS experiments as well as laser desorption ionization (LDI). Thus, despite the relatively low polarity, PAHs have to be considered in the molecular attribution of these model aerosols and/or fresh emissions with low salt content investigated by ESI.

Molecular characterization by ultrahigh resolution mass spectrometry of dissolved black carbon-like molecules in summer along the Pearl River Estuary, China

• Dissolved black carbon molecules in the estuarine DOM are identified. • Numbers and intensity-weighted DBCs decrease gradually with the salinity gradient. • Intensity-weighted molecular weights of DBCs vary from m/z 301.8 to 320.2. • Compounds with O 2-3 and O 10-12 are preferentially eliminated along the PRE. • Condensed aromatic 3 or 4 rings substituted with OH and COOH are proposed. Significant amounts of organic carbon derived from black carbon (BC) are transported annually through the Pearl River Estuary (PRE) in Southern China, into the continental shelf of the South China Sea. However, molecular composition and distribution of dissolved black carbon (DBC) compounds along the PRE are still rarely studied. In this work, dissolved organic matter isolated and extracted by solid phase extraction from water samples collected in summer along the PRE are studied and characterized by negative electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), and with special attention paid to DBC molecules. The numbers and relative intensities of identified DBC molecules (CHO x class) decrease gradually with the salinity gradient from the upper reach to the open water. The DBC molecules accumulated with relatively high intensities in O 7 and O 9 classes in Site A and slightly shifted to O 5 , O 7-8 classes in Site E along the PRE. Possible three or four rings of aromatic ring structure of DBCs, with hydroxyl and carboxy substituent groups are proposed. The relatively smaller sizes of DBCs are likely to have originated from relatively larger oxidized condensed aromatic structures of black carbon. The trend of DBC distribution along the estuary could be explained by DOM degradation in the mixing zone.

Monthly variations of unregulated brominated disinfection by-products in chlorinated water are correlated with total bromine

Brominated disinfection by-products (Br-DBPs) can form during chlorination of drinking water in treatment plants (DWTP). Regulations exist for a small subset of Br-DBPs; However, hundreds of unregulated Br-DBPs have been detected and limited information exists on their occurrence, concentrations, and seasonal trends. Here, a data-independent precursor isolation and characteristic fragment (DIPIC-Frag) method was optimized to screen chlorinated waters for Br-DBPs. There were 553 Br-DBPs detected with m/z values ranging from 170.884 to 497.0278 and chromatographic retention times from 2.4 to 26.2 min. With MS 2 information, structures for 40 of the 54 most abundant Br-DBPs were predicted. The method was then applied to a year-long study in which raw, clear well, and finished water were analyzed monthly. The 54 most abundant unregulated Br-DBPs were subjected to trend analysis. Br-DBPs with higher oxygen-to-carbon (O/C) and bromine-to-carbon (Br/C) ratios increased as water moved from the clear well to the finished stage, which indicated the dynamic formation of Br-DBPs. Monthly trends of unregulated Br-DBPs were compared to raw water parameters such as natural organic matter, temperature, and total bromine, but no correlations were observed. It was found that total concentrations of bromine (TBr) in finished water (0.04–0.12 mg/L) were consistently and significantly greater than in raw water (0.013–0.038 mg/L, P < 0.001), suggesting the introduction of bromine during the disinfection process. Concentrations of TBr in treatment units, rather than raw water, were significantly correlated to 34 of the Br-DBPs at α = 0.05. This study provides the first evidence that monthly trends of unregulated Br-DBPs can be associated with the concentration of TBr in treated waters. - Ultrahigh resolution mass spectrometry was used to identify novel brominated disinfection byproducts in a Canadian water treatment facility. - Several hundred novel brominated compounds were identified of which 54 were assigned chemical structures. - Seasonal variation in the generated DBPs were assessed over 11 months of sampling. - Increases in total bromine in drinking water was noted with progress thru the treatment process.

[Determination of free amino acids in Eriocheir sinensis by ultra-high performance liquid chromatography-high resolution mass spectrometry].

游离氨基酸不仅是一类重要的营养物质,更与中华绒螯蟹独特的滋味和香味密切相关。对游离氨基酸含量进行测定,能为中华绒螯蟹产品的品质评价和风味研究提供有价值的信息。该工作通过优选提取溶剂、优化仪器测定参数,最终使用5%(v/v)高氯酸水溶液提取目标物,采用XDB-C18色谱柱(100 mm×4.6 mm, 1.7 μm),以0.1%(v/v)甲酸水溶液-乙腈为流动相进行梯度洗脱,在电喷雾正离子电离、选择离子扫描模式下进行检测,外标法定量,建立了超高效液相色谱-高分辨质谱(UHPLC-HRMS)测定中华绒螯蟹中17种游离氨基酸含量的方法。结果表明,17种氨基酸在10.0~200.0 mg/L范围内线性关系良好,相关系数(R2)≥0.9990,仪器检出限为0.3 mg/L,仪器定量限为1.0 mg/L。在中华绒螯蟹可食部分中按三水平进行加标回收试验,各目标物的回收率在78.4%~105.3%之间。通过对仪器和方法精密度进行评估,发现17种氨基酸测定仪器重复性的RSD≤4.2%,方法重复性试验的RSD≤5.2%,再现性试验的RSD≤11.4%,精密度数据均在合理范围内。利用该研究建立的检测方法对20个中华绒螯蟹样本进行了实际样品检测,总结了17种游离氨基酸在蟹肉、蟹膏、蟹黄中的分布特点,验证了该方法是一种前处理简便、选择性好、准确度高的检测技术。

Molecular characteristics, sources and environmental risk of aromatic compounds in particulate matter during COVID-2019: Nontarget screening by ultra-high resolution mass spectrometry and comprehensive two-dimensional gas chromatography.

Aromatic compounds, including many polycyclic aromatic hydrocarbons (PAHs), are suspected carcinogens and may originate from different sources. To investigate the impact of anthropogenic emission reductions on unknown aromatic compounds in particulate matter, we collected samples during the pre-COVID period in 2020, the COVID-19 lockdown period in 2020, and the same period as the lockdown in 2019. Besides the 16 PAHs, other aromatic compounds were analyzed by Fourier transform ion cyclotron resonance mass spectrometry and comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry. Four main compound classes were identified: CH, CHO, CHNO, and CHOS. Hierarchical cluster analysis showed the aromatic compounds varied during the different periods. Compared with before the pandemic, the relative abundances of aromatic compounds with low degrees of unsaturation and long alkyl chains (e.g., alkylbenzenes) increased. These compounds probably mainly arose from fossil fuel combustion and petrochemical industry emissions. The CHO compounds, which were dominated by those with high degrees of oxidation, might originate from secondary organic aerosols. Aromatic aldehydes (e.g., cyclamen aldehyde) and benzoates (e.g., 2-ethylhexyl benzoate) probably with high toxicity deserve more attention. During lockdown, nitro derivatives of condensed PAHs were the main CHNO compounds, and the numbers of homologs decreased perhaps because of significant reductions in NOx and PAHs. CHOS compounds with long carbon chains and low degrees of unsaturation were predominant and the numbers of homologs increased. Five compounds (e.g. 1,3-dimethyl pyrene) were predicted to possibly exhibit persistent and bio-accumulated by EPI Suite model, which need further research. The results provide insight on aromatic compounds and their source appointment in atmospheric particulate matter.