Time-of-flight Mass Spectrometry Research Articles

Determination of twelve neonicotinoid pesticides in chili using an improved QuEChERS method with UPLC-Q-TOF/MS

In this study, a QuEChERS method based on citrate was developed and utilized for the analysis of twelve neonicotinoid pesticides in fresh red chilies, fresh green chilies, and dried chilies, coupled with ultra-high performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-Q-TOF/MS). In the sample preparation, acetonitrile containing 1% formic acid was used as the extraction solvent. Anhydrous sodium sulfate replaced the traditional anhydrous magnesium sulfate for water removal, effectively eliminating the issues of salt caking. Graphitized carbon black, octadecyl silica, and primary secondary amine were used as cleaning agents. The method showed good sensitivity, with the limits of quantification below 0.03 mg/kg for fresh chilies and below 0.15 mg/kg for dried chilies. Values of matrix effects ranged from −19.5% to 8.4%, and the recovery was 86.9% - 105.2%. The analytical method provided an effective tool for the high throughput detection of neonicotinoid pesticide residues in multiple chili matrices.

Characterization of banned colorants in cosmetics: A tandem mass-based molecular networking approach

Colorants have been a staple in the cosmetics industry for a considerable time, although certain varieties have been banned owing to health risks. Detecting and confirming these banned colorants simultaneously poses several challenges when employing LC–MS/MS. Molecular networking is a promising analytical technology that can be used to predict the structure of components and the correlation between them using structural and MS/MS spectral similarities. Molecular networking entails assessing the number of fragmented ions and the cosine score (the closer it is to one, the higher the similarity). In this study, we developed and verified a method for the simultaneous quantitative analysis of the 26 banned colorants in cosmetics using LC–MS/MS. Additionally, we propose a novel approach that combines LC–Q–TOF–MS and molecular networking technology to detect banned colorants in cosmetics. For successful molecular networking, a minimum of six fragment ions with cosine scores exceeding 0.5 is required. We developed a screening method for characterizing banned colorants using molecular networking based on LC–TOF–MS results for 26 banned colorants. Furthermore, we demonstrated that our established method can be used for screening by analyzing actual cosmetics (eyebrow tattoo, lipstick tattoo, and hair tint) spiked with three non-targeted banned colorants with similar structures (m/z 267.116, 315.149, and 345.157) in cosmetics. The combination of molecular networking techniques and LC–MS/MS proves highly advantageous for the swift characterization and screening of non-targeted colorants in cosmetics.

In vivo profiling of phytocannabinoids in Cannabis spp. varieties via SPME-LC-MS analysis

BackgroundIn vivo solid-phase microextraction (SPME) is a minimally invasive, non-exhaustive sample-preparation technique that facilitates the direct isolation of low molecular weight compounds from biological matrices in living systems. This technique is especially useful for the analysis of phytocannabinoids (PCs) in plant material, both for forensic purposes and for monitoring the PC content in growing Cannabis spp. plants. In contrast to traditional extraction techniques, in vivo SPME enables continuous tracking of the changes in the level of PCs during plant growth without the need for plant material collection. In this study, in vivo SPME utilizing biocompatible C18 probes and liquid-chromatography coupled to quadrupole time-of flight mass spectrometry (LC-Q-TOF-MS) is proposed as a novel strategy for the extraction and analysis of the acidic forms of five PCs in growing medicinal cannabis plants. ResultsThe SPME method was optimized by testing various parameters, including the extraction phase (coating), extraction and desorption times, and the extraction temperature. The proposed method was validated with satisfactory analytical performance regarding linearity (10–3000 ng/mL), limits of quantification, and precision (relative standard deviations below 5.5 %). The proposed method was then successfully applied for the isolation of five acidic forms of PCs, which are main components of growing medicinal cannabis plants. As a proof-of-concept, SPME probes were statically inserted into the inflorescences of two varieties of Cannabis spp. plants (i.e., CBD-dominant and Δ9-THC-dominant) cultivated under controlled conditions for 30 min extraction of tetrahydrocannabinolic acid (Δ9-THCA), cannabidiolic acid (CBDA), cannabigerolic acid (CBGA), cannabiviarinic acid (CBVA), and tetrahydrocannabivarinic acid (THCVA). Significance and noveltyThe results confirmed that the developed SPME-LC-Q-TOF-MS method is a precise and efficient tool that enables direct and rapid isolation and analysis of PCs under in vivo conditions. The proposed methodology is highly appealing option for monitoring the metabolic pathways and compositions of multiple PCs in medicinal cannabis at different stages of plant growth.

Trends in viable microbial bioburden on surfaces within a paediatric bone marrow transplant unit

Despite their role being historically overlooked, environmental surfaces have been shown to play a key role in the transmission of pathogens causative of healthcare-associated infection. To guide infection prevention and control (IPC) interventions and inform clinical risk assessments, more needs to be known about microbial surface bioburdens. To identify the trends in culturable bacterial contamination across communal touch sites over time in a hospital setting. Swab samples were collected over nine weeks from 22 communal touch sites in a paediatric bone marrow transplant unit. Samples were cultured on Columbia blood agar and aerobic colony counts (ACC) per 100cm2 were established for each site. Individual colony morphologies were grouped and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry or 16s rDNA sequencing. Highest mean counts were observed for sites associated with ward management activity and computer devices (3.29 and 2.97 ACC/100cm2 respectively). A nurses' station keyboard had high mean ACC/100cm2 counts (10.67) and diversity, while laundry controls had high mean ACC/100cm2 counts (4.70) and low diversity. Micrococcus luteus was identified in all sampling groups. Clinical staff usage sites were contaminated with similar proportions of skin and environmental flora (52.19-46.59% respectively), but sites associated with parental activities were predominantly contaminated by environmental microflora (86.53%). The trends observed suggest patterns in microbial loading based on site activities, surface types and user groups. Improved understanding of environmental surface contamination could help support results interpretation and IPC interventions, improving patient safety.

Burkholderia cepacia: Understanding Pathogenicity, Virulence Factors, and Therapeutic Strategies

Burkholderia cepacia, formerly described as Pseudomonas cepacia, belongs to the Burkholderia cepacia complex (Bcc), a collection of closely related gram-negative bacteria that is considered a leading organism in causing pulmonary infections in humans. In healthcare settings, Burkholderia species have the ability to colonise medical equipment and surfaces, posing a threat of nosocomial infections. Moreover, they exhibit inherently resistance to various classes of antibiotics, thus being nominated as multi-drug resistant pathogens (MDR), that is why treatment of infections caused by these organisms is challenging. Enzymes such as metalloproteases, serine proteases, metalloproteases, and other extracellular lipases play a major role in its pathogenesis. In addition to this, different components, such as pili, flagella, and lipopolysaccharide (LPS), have a role in both the motility of the bacterial cell as well as its adherence to host cells. Identification is usually done with different biochemical reactions such as late oxidase activity, oxidation of glucose, variable lysine decarboxylation, maltose, mannitol, and lactose, and hydrogen sulphide gas production. Advanced techniques like semi-nested PCR, real-time PCR, or MALDI-TOF mass spectrometry enable quick and precise identification.
 Key words: Multi-drug resistant, Polymerase chain reaction, Burkholderia cepacia complex, matrix assisted laser desorption ionisation, time of flight mass spectrometry

A high resolution reaction microscope with universal two-region time-focusing method.

This paper presents a novel reaction microscope designed for ion-atom collision investigations, established at the Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China. Its time-of-flight (TOF) spectrometer employs an innovative flight-time focusing method consisting of two acceleration regions, providing optimal time focusing conditions for charged fragments with diverse initial velocities. The TOF spectrometer's axis intentionally tilts by 12° relative to the ion beam direction, preventing potential obstructions from the TOF grid electrodes. The introduced focusing method allows for a flexible time-focusing TOF spectrometer design without restricting the length ratio of the two regions. In addition, this configuration in our case significantly suppresses noise on the recoil ion detector produced by residual gas in the ion beam trajectory, which is a considerable challenge in longitudinal spectrometers. In a test experiment on the single electron capture reaction involving 62.5 keV/u He2+ ions and a helium atomic beam, the recoil longitudinal momentum resolution achieved 0.068 atomic units. This novel configuration and successful test run show excellent precision for ion-atom collision studies.

An LC-MS/MS method for the determination of W18 in urine samples

IntroductionSynthetic drugs pose one of the most significant drug problems worldwide. In this category, W18 emerges as a potent drug of abuse chemically related to fentanyl. W18 has an analgesic potency 10,000 times greater than morphine. Recent in-vitro studies reported no activity of W18 towards opioid receptors. However, its presence in seized drug samples indicates its use as a precursor in fentanyl synthesis. This emphasizes the need to develop methods for its detection in developing countries dealing with emerging new drugs.ObjectivesTo develop an analytical method for the determination of W18 in urine samples.MethodsStandards with W18 concentrations ranging from 5-500 ng/ml were prepared in negative urine along with deuterated internal standard. The samples were diluted with methanol, centrifuged and the supernatant was subjected to Liquid chromatography-tandem mass spectrometry (LC-MS-MS) with time of flight (QTOF) analysis. For chromatographic separation, a C18 column with 50 degrees oven temperature was used. The mobile phase consists of formic acid, water, and acetonitrile. The TOF MS was operated in positive ion mode and multiple reaction monitoring was used for quantification.ResultsThe retention time of W18 was obtained at 9.57 minutes. The parent ion with molecular weight 422.1 along with precursor ions Q1-273, Q2-111.0, Q3-150.0 g/mol were measured. The area of the standards ranges from 1 to 9.0 log 5 with R square of 0.99. The limit of detection (LOD) and quantitation were 5 and 20 ng/ml respectively. The recovery of W18 was estimated to be 96% from the from spiked urine standards.ConclusionsThe developed method is able to detect W18 presence in urine samples. This method has the potential to be used in clinical and research studies.Disclosure of InterestNone Declared

Ultrafast and nanomolar detection of Al3+: Furazan based fluorescent chemosensor and its practices in Smartphone, test kit, water samples and living–cell

A new fluorescent chemoprobe (SDAF) was successfully synthesized and utilized as a sensor for the recognition of Al3+ in EtOH:HEPES (3:2, v:v, pH: 7.0) media. The SDAF depicted a selective “turn–on” response at λem = 467 nm to Al3+ over competitive cations, and the SDAF–Al3+ complex had a reversible response with F−. The limit of detection (LOD) was found about at nano–molar level (28.0 nM), demonstrating the sensitivity of the chemoprobe toward Al3+. The binding stoichiometry of SDAF–Al3+ was investigated by TOF–MS, Job's plot, 1H NMR and 13C NMR methods and found as 1:1. The recognition mechanisms of SDAF for the detection of Al3+ were the –C = N isomerization and photoinduced electron transfer (PET) mechanisms, and they were confirmed by density functional theory (DFT) computation. Furthermore, the SDAF was successfully employed in living–cell bioimaging and cytotoxicity, it was also utilized in Smartphone, test–kit and natural spring water (recovery values; 89.01 %– 96.33 %)applications.

Discriminatory power of MALDI-TOF MS protein profiling analysis of pork meat and meat products

Forty different sample preparation methods were tested to obtain the most informative MALDI-TOF MS protein profiles of pork meat. Extraction by 25% formic acid with the assistance of zirconia-silica beads followed by defatting by methanol:chloroform mixture (1:1, v/v) and deposition by using the layer-by-layer method was determined as the optimum sample preparation protocol. The discriminatory power of the method was then examined on samples of pork meat and meat products. The method was able to discriminate between selected salami based on the production method and brand and was able to monitor the ripening process in salami. However, it was not able to differentiate between different brands of pork ham or closely located parts of pork meat. In the latter case, a more comprehensive analysis using LC-MS/MS was used to assess the differences in protein abundance and their relation to the outputs of MALDI – TOF MS profiling.

Multidrug-Resistant Staphylococcus sp. and Enterococcus sp. in Municipal and Hospital Wastewater: A Longitudinal Study.

The objective of the study was to detect multidrug-resistant Staphylococcus sp. and Enterococcus sp. isolates in municipal and hospital wastewater and to determine their elimination or persistence after wastewater treatment. Between August 2021 and September 2022, raw and treated wastewater samples were collected at two hospital and two community wastewater treatment plants (WWTPs). In each season of the year, two treated and two raw wastewater samples were collected in duplicate at each of the WWTPs studied. Screening and presumptive identification of staphylococci and enterococci was performed using chromoagars, and identification was performed with the Matrix Assisted Laser Desorption Ionization Time of Flight mass spectrometry (MALDI-TOF MS®). Antimicrobial susceptibility was performed using VITEK 2® automated system. There were 56 wastewater samples obtained during the study period. A total of 182 Staphylococcus sp. and 248 Enterococcus sp. were identified. The highest frequency of Staphylococcus sp. isolation was in spring and summer (n = 129, 70.8%), and for Enterococcus sp. it was in autumn and winter (n = 143, 57.7%). Sixteen isolates of Staphylococcus sp. and sixty-three of Enterococcus sp. persisted during WWTP treatments. Thirteen species of staphylococci and seven species of enterococci were identified. Thirty-one isolates of Staphylococcus sp. and ninety-four of Enterococcus sp. were multidrug-resistant. Resistance to vancomycin (1.1%), linezolid (2.7%), and daptomycin (8.2%/10.9%%), and a lower susceptibility to tigecycline (2.7%), was observed. This study evidences the presence of Staphylococcus sp. and Enterococcus sp. resistant to antibiotics of last choice of clinical treatment, in community and hospital wastewater and their ability to survive WWTP treatment systems.

Identification and characterization of the in-vivo metabolites of the novel soluble epoxide hydrolase inhibitor EC5026 using liquid chromatography quadrupole time of flight mass spectrometry

EC5026 is a novel soluble epoxide hydrolase inhibitor being developed clinically to treat neuropathic pain and inflammation. In the current study, we employed the LC-ESI-Q-TOF-MS/MS technique to identify four in-vivo phase-I metabolites of EC5026 in rat model, out of which three were found to be novel. The identified metabolites include aliphatic hydroxylation, di-hydroxylation, terminal desaturation, and carboxylation. No phase-II metabolites were found. The pharmacokinetic profile of identified metabolites was established after a single oral dose of EC5026 to Wistar rats. The Tmax of the drug and metabolites were found to be in the range of 1–2 hours and 4–12 hours, respectively. The major metabolites M1 and M2 were found to have more than 2-fold (263.87% AUC) and equivalent exposure (96.33% AUC) compared to the parent drug, respectively. Further, the docking study revealed that the mono-hydroxylated and terminally desaturated metabolites possess better binding affinity than the parent drug. Therefore, these metabolites may hold sEH inhibition potential and can be followed through future research.

Chemical characterization of different parts of Forsythia suspensa and α-glucosidase and pancreatic lipase inhibitors screening based on UPLC-QTOF-MS/MS and plant metabolomics analysis

Forsythia suspensa (Thunb.) Vahl (FS) is an important plant with high edible and medicinal values. The edible fruit of FS is a common traditional medicine in China, Japan and Korea. Compared to the research on the phytochemistry and pharmacology of the fruits, study on the other parts of FS, such as leaves and flowers is still limited. In this study, an integrated strategy based on ultra-performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-QTOF-MS/MS), plant metabolomics and correlation analysis was established for comprehensively chemical characterization of fruits, leaves and flowers of FS, and discovery of α-glucosidase and pancreatic lipase inhibitory metabolites. The plant metabolic profiling of fruits, leaves and flowers of FS was performed by UPLC-QTOF-MS/MS, and a total of 74 secondary metabolites, including 15 phenylethanoid glycosides, 20 lignans, 10 cyclohexanol derivatives, 11 organic acids, 9 flavonoids, 3 triterpenes, and 10 other compounds were identified. Then, 29 differential secondary metabolites that responsible to distinguish the fruits, leaves and flowers of FS were further screened out by multivariate statistical analysis. Meanwhile, the α-glucosidase and pancreatic lipase inhibition of different parts of FS were evaluated and compared by in vitro experiments. The results demonstrated that the leaves of FS showed the highest inhibition on α-glucosidase and pancreatic lipase with IC50 of 0.17 ± 0.04 mg/mL and 0.56 ± 0.33 mg/mL, respectively. Then, the correlation between differential metabolites and enzyme inhibitory activities were investigated by Pearson correlation analysis, and 12 potential α-glucosidase and pancreatic lipase inhibitors were screen out. Additionally, the α-glucosidase and pancreatic lipase inhibitory activities of five potential enzyme inhibitory components, including quercitrin, rutin, kaempferol-3-O-rutinoside, pinoresinol-4-O-glucoside and phillyrin were further validated by in vitro assays and molecular docking analysis. The results showed that all the five potential inhibitors showed good inhibitory effects on α-glucosidase and pancreatic lipase, and the binding of the five inhibitors to enzymes mainly through hydrogen bonding, hydrophobic force, and ionic bonding. This study provided a feasible strategy for comparison and discrimination of different parts of medicinal plant and discovery of bioactive components, and also provided useful information for future utilization of different parts of FS.

Profiling and characterization of the constituents of taibai ginseng using ultra‐high performance liquid chromatography‐quadrupole time of flight mass spectrometry

AbstractTaibai ginseng (roots of Pedicularis decora Franch.) has been reported to possess anti‐Alzheimer's disease (anti‐AD) activity and can be potentially used for treating AD. However, the chemical constituents of taibai ginseng have not yet been elucidated because of the paucity of relevant studies, which hinders further research on the pharmacological mechanism and utilization of taibai ginseng. In this study, a rapid and efficient method for comprehensively analyzing the chemical constituents of taibai ginseng was established for the first time. We used ultra‐high performance liquid chromatography‐quadrupole time of flight mass spectrometry in combination with the UNIFI data‐processing platform to automatically characterize and identify the chemical profile of taibai ginseng. As a result, more than 76 compounds were detected, and their structures were characterized. These compounds include 24 iridoid glycosides, 24 phenylethanol glycosides, 15 terpenoids, and 13 other components. More than fifty of these compounds from taibai ginseng were reported for the first time. Our results provide a reference for the quality control of taibai ginseng and establish a higher quality standard for pharmacodynamic research. Appropriate modification of the method reported herein can enable its use for the screening and characterization of taibai ginseng and other compounds from the Pedicularis genus.

Comparing massa medicata fermentata before and after charred in terms of digestive promoting effect via metabolomics and microbiome analysis

Ethnopharmacological relevanceMassa Medicata Fermentata, a fermented Chinese medicine, is produced by the fermentation of six traditional Chinese medicines. Liu Shenqu (LSQ) and charred Liu Shenqu (CLSQ) have been used for strengthening the spleen and enhancing digestion for over a thousand years, and CLSQ is commonly used in clinical practice. However, it is unclear whether there is a difference in the spleen strengthening and digestion effects between LSQ and CLSQ, as well as their mechanisms of action. Aim of studyThis study aims to compare the effects of LSQ and CLSQ on the digestive function of functional dyspepsia (FD) rats and reveal their mechanisms of action. Materials and methodsSPF grade SD rats were randomly divided into 6 groups: control group, model group, Liu Shenqu decoction low-dosage (LSQ LD) group, Liu Shenqu decoction high-dosage (LSQ HD) group, charred Liu Shenqu decoction low-dosage (CLSQ LD) group, and charred Liu Shenqu decoction high-dosage (CLSQ HD) group. Rats were injected intraperitoneally with reserpine to create an FD model and then treated by intragastric administration. During this period, record the weight and food intake of the animals. After 18 days of treatment, specimens of the gastric antrum, spleen, and duodenum of rats were taken for pathological staining and immunohistochemical detection of Ghrelin protein expression. Enzyme linked immunosorbent assay (ELISA) was used to determine the concentration of relevant gastrointestinal hormones in serum. The 16 S rDNA sequencing method was used to evaluate the effect of cecal contents on the structure of the gut microbiota in experimental rats. Plasma metabolomics analysis was performed using ultra high performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (UPLC-QTOF-MS) to further reveal their mechanism of action. ResultsLSQ and CLSQ improved the pathological tissue histological structure of FD rats and increased the levels of MTL and GAS hormones in serum and the levels of ghrelin in the gastric antrum, spleen, and duodenum, while reducing VIP, CCK, and SP hormone levels. The above results showed that the therapeutic efficacy of CLSQ is better than that of LSQ. Futhermore, the mechanism of action of LSQ and CLSQ were revealed. The 16 S rDNA sequencing results showed that both LSQ and CLSQ can improve the composition and diversity of the gut microbiota. And metabolomic analysis demonstrated that 20 metabolites changed after LSQ treatment, and 16 metabolites underwent continuous changes after CLSQ treatment. Further analysis revealed that LSQ mainly intervened in the metabolic pathways of glycerol phospholipid metabolism and arginine and proline metabolism, but CLSQ mainly intervened in the metabolic pathways of ether lipid metabolism, sphingolipid metabolism, and glycerophospholipid metabolism. ConclusionsBoth LSQ and CLSQ can improve functional dyspepsia in FD rats, but CLSQ has a stronger improvement effect on FD. Although their mechanisms of action are all related to regulating gastrointestinal hormone secretion, significantly improving intestinal microbiota disorders, and improving multiple metabolic pathways, but the specific gut microbiota and metabolic pathways they regulate are different.

Factors affecting the quality and reproducibility of MALDI-TOF MS identification for human Capnocytophaga species

Reproducibility and quality of MALDI-TOF MS spectra are critical in the identification process, however, information on the factors affecting the identification scores are scarce. Here, we studied the influence of various factors during the identification process of human oral Capnocytophaga species. The influence of two incubation times, plate-spotting reproducibility of two examiners, extraction technique, storage period of plates, and different laser repetition rates on the quality of MALDI-TOF MS identification of 34 human Capnocytophaga strains (including C. gingivalis, C. granulosa, C. haemolytica, C. leadbetteri, C. ochracea, C. sputigena, and Capnocytophaga genospecies AHN8471) was examined. The identification rate did not show a significant difference (P = 0.05) between the two incubation times, except that C. haemolytica needed a longer incubation time to be recognized at the genus level. The reproducibility of spotting between two examiners was ensured by following the manufacturer's instructions. At the species level, formic acid extraction improved the identification of species with limited representation in the database, such as C. haemolytica and C. granulosa. The storage of plates for one week decreased the identification scores. No significant difference (P = 0.39) was observed between the 60 Hz and 120 Hz laser repetition rates for identifying Capnocytophaga species to the genus or species level. In conclusion, the MALDI TOF MS offers a reliable Capnocytophaga identification after following the universal protocol, while the formic acid extraction is restricted to species with a limited number of strains in the database.

Development of Catharanthus callus cell lines for indole-derived alkaloids production

In this work, we evaluated the effect of 29 PGR combinations and photoperiods on callogenesis while analyzing the fate of calluses during a two-year period. Variation of PGR combinations in the culture medium strongly affected callogenesis in terms of growth and callus morphology. Although most PGR combinations resulted in callogenesis, only few ones supported cell survivor in long-term basis for the generation of cell lines as homogenous-looking calluses. Analysis by tandem liquid chromatography quadrupole time of flight mass spectrometry (LC-QTOF-MS/MS) revealed production of vincristine (9.25 mg/kg), vinblastine (0.17 mg/kg), and vindoline (1.02 mg/kg) in cell lines when proper combinations of PGR are employed. These callus cell lines are a promising platform to establish suspension cultures seeking production of alkaloids, particularly vincristine and vinblastine.

Targeted screening and quantification of flavonoids in the flavedo of navel oranges at different growth stages based on metabolomics technology

Plant-based food intake is essential for health promotion, especially in preventing chronic diseases. Flavonoids, as important bioactive substances found in citrus fruits, have a variety of health benefits, including antioxidant, anti-inflammatory, and cancer-inhibiting properties. This study used ultra-high performance liquid chromatography tandem quadrupole time of flight mass spectrometry to determine the flavonoids in the flavedo of navel oranges at different growth stages. Combined with chemometric methods to distinguish flavonoids at different growth stages, 15 differential flavonoids were deduced. In addition, the biomarker flavonoids in navel orange flavedo were quantified by high performance liquid chromatography mass spectrometry. The results showed that the contents of rutin, isosinensetin, and isorhamnetin all showed a trend of increasing and then decreasing during the growing period, while the contents of tangeretin and nobiletin would gradually decrease with the increase of fruit maturity. In addition, the analysis also revealed that the content of isorhamnetin was negatively correlated with the content of both narirutin and tangeretin, and it was hypothesized that isorhamnetin was in the same metabolic branching pathway as narirutin or tangeretin. The results of this study support the practical application of orange peel as a nutritional resource in functional foods.

Study of secondary organic aerosol formation and aging using ambient air in an oxidation flow reactor during high pollution events over Delhi

Secondary aerosols constitute a significant fraction of atmospheric aerosols, yet our understanding of their formation mechanism and fate is very limited. In this work, the secondary organic aerosol (SOA) formation and aging of ambient air of Delhi are studied using a potential aerosol mass (PAM) reactor, an oxidation flow reactor (OFR), coupled with aerosol chemical speciation monitor (ACSM), proton transfer reaction time of flight mass spectrometer (PTR-ToF-MS), and scanning mobility particle sizer with counter (SMPS + C). The setup mimics atmospheric aging of up to several days with the generation of OH radicals. Variations in primary volatile organic compounds (VOCs) and oxygenated volatile organic compounds (OVOCs) as a function of photochemical age were investigated. Primary VOCs such as benzene, toluene, xylene, trimethyl benzene, etc. decrease and OVOCs like formic acid, formaldehyde, acetone, ethanol, etc. increase substantially upon oxidation in OFR. The highest organic aerosol (OA) enhancement was observed for the 4.2 equivalent photochemical days of aging i.e., 1.84 times the ambient concentration, and net OA loss was observed at very high OH exposure, typically after 8.4 days of photochemical aging due to heterogeneous oxidation followed by fragmentation/evaporation. In ambient air, OA enhancement is highest during nighttime due to the high concentrations of precursor VOCs in the atmosphere. SMPS + C results demonstrated substantial new particle formation upon aging and decrement in preexisting aerosol mass. This is the first experimental study conducting an in-situ evaluation of potential SOA mass generated from the ambient aerosols in India.

Sustainable bio-based solid phase extraction adsorbent for the determination of various types of organic compounds.

A sustainable, bio-based, mesoporous material, Starbon A800, was explored for use as an adsorbent in solid phase extraction (SPE). A solution containing seven nitrosamines was first used as a standard to optimise conditions for extraction efficiency with Starbon A800. After optimising conditions, 25 compounds of varying polarity (terpenes, phenolics, pesticides, PAHs, amines, and nitrosamines) were extracted with SPE using either Starbon® A800, C18 or Porous Graphitic Carbon (PGC) as the adsorbent, for comparison purposes. At the same time, 3 different elution solvents (heptane, dichloromethane, and ethanol) were used for each type of adsorbent. Hansen solubility parameters can be used to choose an appropriate elution solvent for the selected SPE adsorbent. The best average SPE recoveries found for the 25 various compounds were 83%, 79%, and 65% using Starbon A800, PGC, and C18 adsorbents respectively and these had dichloromethane as the elution solvent. The identification and quantification of components was carried out using UV-visible spectroscopy, two-dimensional gas chromatography (GCxGC) with time of flight/mass spectrometry (TOF/MS) or a nitrogen chemiluminescence detector (NCD). The optimized method was successfully applied to extract volatile organic compounds from red wine and tap water using Starbon A800. Starbon A800 was shown to be a promising, low-cost, green, scalable, alternative adsorbent for the extraction of various types of organic compounds of a wide range of polarities using SPE.

Antagonistic Effects of Lactic Acid Bacteria Isolated from Ethiopian Traditional Fermented Foods and Beverages Against Foodborne Pathogens.

Lactic acid bacteria (LAB) found in Ethiopian traditional fermented foods and beverages have potential antagonistic effects against foodborne pathogens due to their capacity to produce various antimicrobial metabolites. This study evaluated the antagonistic activity of LAB isolated from Ethiopian traditional fermented foods and beverages against foodborne pathogens and characterized their antimicrobial substances. A total of 180 traditional fermented foods and beverages were collected, and the antagonistic activities of LAB were evaluated against selected foodborne pathogens. The effects of pH, temperature, enzymes, and food additives on the antagonistic effects of cell-free supernatant produced by LAB were investigated. LAB identification and characterization were conducted using an integrated phenotypic approach and MALDI TOF MS spectrum analysis, and data were analyzed using one-way ANOVA and Tukey post hoc analysis. A total of 956 LAB were isolated, of which seventeen (17 LAB) isolates of Pediococcus pentosaceus (Pc. pentosaceus (n = 7)), Pediococcus acidilactici (Pc. acidilactici (n = 2)), Enterococcus faecium (Ec. faecium (n = 6)), and Lactococcus lactis (Lc. lactis (n = 2)) were screened for antagonistic activity based on their ability to produce bacteriocins, probiotic activity, and preservative potential. Pc. pentosaceus JULABB16, Pc. pentosaceus JULABB01, and Ec. faecium JULABBr39 showed strong antagonistic activity against all pathogens, with mean inhibition zone diameters ranging from 23.50 to 35.50mm. Lc. lactis, Pc. pentosaceus, Pc. acidilactici, and Ec. faecium produced bioactive metabolites that were sensitive to proteolytic enzymes and capable of withstanding high temperatures (80-100°C) and acid concentrations (pH 2-10). The CFS produced by Lc. lactis, Pc. pentosaceus, Pc. acidilactici, and Ec. faecium showed the most impending antagonistic activity against all pathogens. The bioactive substances produced by LAB isolates had promising effects against food spoilage and pathogenic bacteria, making them potential natural food preservatives.