Pyrolysis-gas Chromatography-mass Spectrometry Analysis Research Articles

Identification and Characterization of Mercury Contamination in Vegetables and Herbs Cultivated on a Commercial Vertical Indoor Farming System with Light-Emitting Diode Lighting: Unveiling an Unusual Food Safety Risk of Some Improperly Manufactured High-Density Agricultural Production Systems.

Artificial grow lights, such as light-emitting diodes (LEDs) and fluorescent grow lights, are commonly used in modern day indoor farming, citing advantages in energy efficiency and a higher controlled environment. However, the use of LEDs poses a risk in mercury contaminations as a result of its production process, specifically LEDs with polyurethane encapsulates that were traditionally produced using mercury resins as a catalyst. A total of 10.0 ppm of mercury was detected in a curly kale sample harvested from an indoor hydroponic vegetable farm, exceeding Singapore Food Regulation's limit of 0.05 ppm. Vegetables, farming inputs, and surface swabs from the affected farm were analyzed using wet acid digestion followed by cold vapor atomic absorption spectroscopy analysis. The investigation found high concentrations of mercury in the LED encapsulant, and the encapsulant material was identified to be polyurethane by Fourier transform infrared spectroscopy and pyrolysis-gas chromatography-mass spectrometry analysis, indicating the source of mercury contamination to be the LED polyurethane encapsulant.

Rapid Chemical Screening of Microplastics and Nanoplastics by Thermal Desorption and Pyrolysis Mass Spectrometry with Unsupervised Fuzzy Clustering.

The transport and chemical identification of microplastics and nanoplastics (MNPs) are critical to the concerns over plastic accumulation in the environment. Chemically and physically transient MNP species present unique challenges for isolation and analysis due to many factors such as their size, color, surface properties, morphology, and potential for chemical change. These factors contribute to the eventual environmental and toxicological impact of MNPs. As analytical methods and instrumentation continue to be developed for this application, analytical test materials will play an important role. Here, a direct mass spectrometry screening method was developed to rapidly characterize manufactured and weathered MNPs, complementing lengthy pyrolysis-gas chromatography-mass spectrometry analysis. The chromatography-free measurements took advantage of Kendrick mass defect analysis, in-source collision-induced dissociation, and advancements in machine learning approaches for the data analysis of complex mass spectra. In this study, we applied Gaussian mixture models and fuzzy c-means clustering for the unsupervised analysis of MNP sample spectra, incorporating clustering stability and information criterion measurements to determine latent dimensionality. These models provided insight into the composition of mixed and weathered MNP samples. The multiparametric data acquisition and machine learning approach presented improved confidence in polymer identification and differentiation.

Effect of deacetylation of chitosan on physicochemical properties, antioxidant and antibacterial activities of chitosan-mannose derivatives.

This paper investigates the physical, chemical, and antibacterial properties of water-soluble chitosan derivatives. Preparation of the water-soluble chitosan derivatives was done by the Maillard reaction (MR) between chitosan (the degree of deacetylation (DD) being 50%, 70%, and 90%) and mannose. No organic reagent was used in the process. Systematic evaluations of the effects of chitosan DD on the reaction extent, the structure, the composition, as well as the physicochemical properties, antioxidant properties, and bacterial inhibitory properties of the finished chitosan-mannose Maillard reaction products (Mc-mrps) were carried out. Based on the experimental data obtained from the Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Pyrolysis-gas chromatography-mass analysis (PY-GC-MS), and 1H-NMR, the Mc-mrps formed from chitosan with different DDs had different structures and components. An increase in the DD of chitosan led to a significant increase in the degree of reaction, color difference (△E), and solubility (p<0.05). The zeta potential and particle size of the Mc-mrps were also influenced by the DD of chitosan. Additionally, the antimicrobial action against Gram-positive (S.aureus and Bacillus subtilis) and Gram-negative bacteria (E.coli and Salmonella typhimurium) as well as antioxidant activity were enhanced by the incorporation of mannose. This was also achieved by the increase of the DD of chitosan. The results of the study suggest that chitosan was derived with mannose to yield a novel, water-soluble polysaccharide with better antioxidant and antimicrobial activities. The DD of chitosan had a significant effect on the properties of the Mc-mrp, which can serve as a reference point for the subsequent preparation and application of such derivatives. This article is protected by copyright. All rights reserved.

The changes of chemical molecular components in soil organic matter are associated with fungus Mortierella capitata K.

Fungi play essential roles in the turnover of soil organic matter (SOM). However, it is unclear how fungi affect the chemical molecular composition of SOM. This study examined the effect of saprophytic soil fungus Mortierella capitata K on different soil carbon components and their molecular components. Genome sequencing revealed the ability of the strain to synthesize and degrade heterocycles, heteropolysaccharides, alkenes, terpenoids, steroids, amides, lipids, and amino acids. Subsequently, the turnover of SOM in M. capitata K inoculation with straw (KS) or without straw (K) addition was investigated via an aseptic microcosm experiment for 240 days. Pyrolysis gas chromatography-mass spectrometry analysis (Py-GCMS) showed that the molecular composition of SOM significantly changed with culture time in the two treatments. M. capitata K inoculation increased the relative abundance of tetradecanentitrile, dotriacontane, n-hexadecanoic acid, and n-dodecyl methacrylate in SOM during day 5–180. In contrast, the proportion of components in SOM (oxidizable by potassium permanganate) reduced after M. capitata K inoculation. Similarly, M. capitata K inoculation decreased the relative abundance of alkanes, alkenes, and alcohols in the original SOM on the 240th day. However, the above decline was effectively alleviated after straw addition. Straw addition significantly improved the abundance of n-hexadecanoic acid. RNA sequencing on the 30th day revealed the association between genes encoding alcohol dehydrogenase and SOM ester formation. Therefore, this study may provide insights into the complex feedback loops between microbial activities and molecular composition changes in SOM.

First evidence of Opuntia Ficus-Indica leaves used in ancient surface finishing treatments of stone architecture in Salento (Apulia, Italy)

Abstract The application of hydrophobic coatings on the Lecce stone is a widespread practice today to preserve stone monuments from decay. The practice of covering the stone facades of the buildings was also used in the past in Salento (Apulia, Italy): in fact, ancient sources report that natural waterproofing agents were used for esthetic, protective, hygienic and conservative purposes. The materials and methods of preparation of these finishes became often secret of the workshop and were not handed down, and when known, they may have undergone changes over time. The identification of the materials and methodologies used on historical buildings for their protection, plays a major role to establish correct protocols for their restoration. For this purpose, selected religious and civil buildings (based on requirements, such as historical reasons, conservation status, restoration interventions and presence of visible or documented surface treatments), made of Lecce stone and located in the territory of the Salento, were studied and the presence of surface treatments was investigated. Samples were analyzed by pyrolysis-gas chromatography/mass spectrometry analysis (Py-GC/MS) with and without thermally assisted hydrolysis and methylation. The results of the analyses showed that these buildings have been protected with different natural products. This paper, indeed, gives evidences of the presence of surface treatments, i.e. identifies the ancient finishing techniques through diagnostic analyses. Furthermore, for the first time, the identification of chemical biomarkers of prickly pear leaves confirms the use of Opuntia Ficus-Indica in finishing treatments of Lecce stone.

Long-term watershed management is an effective strategy to reduce organic matter export and disinfection by-product precursors in source water

Watershed management practices such as prescribed fire, harvesting and understory mastication can alter the chemical composition and thickness of forest detritus, thus affecting the quantity and quality of riverine dissolved organic matter (DOM). Long-term effects of watershed management on DOM composition were examined through parallel field and extraction-based laboratory studies. The laboratory study was conducted using detritus samples collected from a pair of managed and unmanaged watersheds in South Carolina, USA. Results showed that dissolved organic carbon (DOC), total dissolved nitrogen (TDN) and ammonium (NH4+-N) concentrations were higher in water extracts from the unmanaged watershed than from the managed watershed (P&amp;lt;0.01). Pyrolysis gas chromatography–mass spectrometry analysis showed that water extracts from the unmanaged watershed contained more aromatic compounds than extracts from the managed watershed. For the field study, monthly water samples were collected for 1 year (2015) from the paired watersheds. DOC and TDN concentrations, as well as DOM aromaticity, were significantly higher in the unmanaged watershed than in the managed watershed for most of the year (P&amp;lt;0.05) and were linked to detrital thickness, precipitation and flow patterns. The formation potential of two regulated disinfection by-products was lower in the unmanaged watershed for most of 2015 (P&amp;lt;0.05). From this study, it appears that long-term watershed management practices may alter detrital mass and chemistry in ways that improve water quality.

An efficient flame retardant for epoxy resin: Preparation and pyrolytic behaviour

Using 4,4-diaminodiphenyl methane as a curing agent, three kinds of monomers, 4,4′-dihydroxybenzophenone, diphenyl chlorophosphite and 1,4-phenylene diisocyanate (NCO), were introduced into a thermosetting resin (DGEBA). The flame retardancy properties of the composites were studied, and the results were compared with those of 5 wt% bis(bis(4-((diphenoxyphosphoryl)oxy)phenyl)methyl) 1,4-phenylenedicarbamate (DHPP-OH-NCO), 10 wt% DHPP-OH-NCO and 15 wt% DHPP-OH-NCO curing agents. The results showed that 15 wt% DHPP-OH-NCO had an improved flame retardancy, the limited oxygen index reached 33.5% and the vertical burning test (UL94) achieved a V-0 level. A cone calorimeter experiment showed that the addition of the flame retardant significantly reduced the amount of generated smoke and heat. Macroscopic digital images, scanning electron microscopy images and thermogravimetric analysis results further revealed that the epoxy resin (EP) with DHPP-OH-NCO exhibited greater char yields. The flame retardancy mechanism of the flame retardant was preliminarily shown by pyrolysis–gas chromatography–mass spectrometry analysis. The combined test results demonstrate that a high-efficiency phosphorous-containing flame retardant for EPs was successfully developed.

Effects of forest fire on the properties of soil and humic substances extracted from forest soil in Gunma, Japan.

Increases in global wildfires and fire severity are expected to result from global warming. Severe wildfires not only burn surface vegetation but also affect forest soil. Humic substances play key roles in the transport of nutrients and the carbon cycle in terrestrial ecosystems. In this study, we evaluated the effects of forest fires on the chemical properties of fulvic acid (FA) and humic acid (HA) extracted from non-burned and burned forest soils in Gunma, Japan. The differential thermal analysis of FA indicated that the intensity of exothermic reaction peak at 400°C was 2-fold higher than that from non-burned soil. Based on pyrolysis-gas chromatography-mass spectrometry analysis with tetramethyl ammonium hydroxide, the amount of pyrolysate compounds in FA from burnt soil was significantly lower than that in FA from non-burnt soil. Therefore, we can conclude that the forest fire caused the significant change in the properties of FA such as increasing the aromaticity and refractory. In addition, the concentration of dissolved organic carbon with low molecular weight in surface soil increased after forest fire. This study suggests that the denaturation of soil organic matter by wildfire can affect the carbon cycle in terrestrial ecosystems.

Characterization of the chemical composition of Adenostemma lavenia (L.) Kuntze and Adenostemma platyphyllum Cass

The purpose of this study was to characterize the chemical compounds of Adenostemma lavenia (L.) Kuntze (Al) and Adenostemma platyphyllum Cass (Ap) using Pyrolysis-gas chromatography/mass spectrometry (Py-GCMS) and proximate analysis. Two species of Adenostemma samples (roots, stem and leaves) about 1 mg was pyrolyzed directly at the optimum temperature of 600°C. Py-GCMS was relatively fast, easy to use and without samples preparation and identification of the chemical compounds was carried out by comparison of the mass spectra obtained with those stored in Wiley 7th libraries. The data of proximate analysis were statistically analysed using Friedman test followed and hierarchical cluster analysis (HCA) for data of Py-GCMS. The result of proximate analysis showed that A. lavenia (L.) Kuntze (Al) and A. platyphyllum Cass (Ap) contained 8.27% (Al) and 9.18% (Ap) of water, 11.52% (Al) and 17.84% (Ap) of protein, 5.67% (Al) and 6.33% (Ap) of fat, and 17.32% (Al) and 19.94 (Ap) of ash. Amines, aldehydes, fatty acids, terpenoids-steroids, alkaloids, aromatic and aliphatic hydrocarbons, phenolic, and oligopeptides as part of 125 chemical compounds of each species are identified by Py-GCMS analysis. Hierarchical cluster analysis of pyrolysis products indicate not similitary of major chemical compounds of two Adenostemma species.

Diagenetic transformation of organic matter in the Holocene sediments of the Black Sea: pyrolysis data

The article presents the results of pyrolysis (Rock-Eval) and pyrolysis-gas chromatography-mass spectrometry analysis of organic matter (OM) in the Holocene sediments of the Black Sea. The studied samples represent two parts of the sedimentary column: coccolith ooze with 2.8% Corg at the top and sapropels oozes with 8.5% Corg at the bottom. The deposition of Holocene sediments was inferred to take place under euxinic conditions, which are more favorable for organic-matter preservation and sapropel deposition during the Old Black Sea stage. The results show that the modern processes of microbially mediated methane oxidation in the Old Black Sea oozes are interpreted as the main cause of their apparently lower degree of diagenetic transformation as compared to that of coccolith oozes.

Biomolecular Preservation of Miocene Fossil Liquidambar from Tiantai, China and Clarkia, USA: Implications for Palaeoenvironmental Study

AbstractBiomolecular characteristics of fossil Liquidambar from the Miocene Shengxian Formation, Tiantai, Zhejiang province in eastern China and Miocene Clarkia sediment, Idaho, U.S.A., are obtained by means of Pyrolysis‐Gas chromatography‐Mass spectrometry analysis (Py‐GC‐MS). Their modern equivalent (Liquidambar formosana) collected from Nanjing, eastern China, is also analyzed for comparison. The total ion chromatograms (TIC) of modern L. formosana leaves shows abundant pyrolysates of lignin, polysaccharide, aliphatic acid, and amino acid. However, only one polysaccharide molecule, i.e., levoglucosan, is retained in fossil Liquidambar leaves from the two Miocene sites with the Tiantai specimen possessing higher intensity. As expected, some lignin pyrolysates including benzene, phenol, guaiacol, vinylphenol and their derivatives, are detected in Miocene Tiantai L. miosinica. However, the lignin components with large molecular weight other than benzene and phenol compounds, are absent in Miocene Clarkia L. pachyphyllum. Abundant pristene and homologous series of n‐alk‐1‐ene/n‐alkane pairs with a long retention time are shown in pyrograms of both Tiantai and Clarkia fossils. Based upon our Py‐GC‐MS data, the molecular preservation in these Liquidambar leaf samples can be ranked as the following (from high to low quality respectively): modern sample &gt;Tiantai sample &gt;Clarkia sample. Vinyl phenol, an important compound, is present in modern and Tiantai Liquidambar leaves, while absent in Clarkia sample, implying that vinyl phenol may be sourced from lignin for Liquidambar leaves. Our data support the hypothesis of in situ polymerization for the origin of long‐chain homologous series of n‐alk‐1‐ene/n‐alkane pairs as leaf alteration products. Our data have implications of the impact of leaf degradation toward biases for palaeoenvironmental reconstruction using stable carbon isotope of fossil plants, and suggest the importance of evaluating molecular preservation of fossil leaf tissues prior to the application of carbon isotope compositions of fossil leaves.

Thermal degradation behavior and gas phase flame‐retardant mechanism of polylactide/PCPP blends

ABSTRACTThe thermal degradation behavior of the blend based on polylactide (PLA) and poly(1,2‐propanediol 2‐carboxyethyl phenyl phosphinate) (PCPP) was investigated by the thermogravimetric analysis (TGA). Thermal degradation activation energies (Ea) of neat PLA and PLA/15% PCPP blend were calculated via the Flynn–Wall–Ozawa method. The Ea of the blends increased with the addition of PCPP increasing when the conversion was higher than 10%. In addition, the appropriate conversion models for the thermal degradation process of PLA and PLA/15% PCPP were studied via the Criado method. At the same time, the main gaseous decomposition products of PLA and its blend were identified by TGA/infrared spectrometry (TGA–FTIR) analysis. And it revealed that the PCPP improved the flame‐retardant property of PLA via altering the release of the flammable gas and nonflammable gas. Moreover, the PCPP improved the flame‐retardant property of PLA by inhibiting exothermic oxidation reactions in the combustion, which was further proved by pyrolysis–gas chromatography–mass spectrometry analysis. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40480.

Calcium and aluminum-based fillers as flame-retardant additives in silicone matrices. III. Investigations on fire reaction

The flame retardancy of silicone composites containing calcium- and aluminum-based fillers has been investigated using several methods including cone calorimeter, Pyrolysis Combustion Flow Calorimeter (PCFC), thermogravimetric analysis and pyrolysis-gas chromatography-mass spectrometry analysis (Py-GC/MS). The fire reaction of precipitated calcium carbonate, calcite, calcium hydroxide, aluminum trihydrate, boehmite and alumina-based composites was correlated mainly with their thermal stability, while for mica and wollastonite-based composites, a barrier effect was also evidenced. The endothermic effect was not established as an efficient flame retardancy mechanism for the silicone composites containing hydrated fillers. Mica composite exhibited the best flame retardancy, in terms of depressed HRR, among all investigated formulations. Finally, a unique behavior was observed during the cone calorimeter test of calcium hydroxide-based composite, which co-crystallization with silica occurs exclusively at high heat flux.

Characterisation of permanent markers by pyrolysis gas chromatography–mass spectrometry

Pyrolysis gas chromatography-mass spectrometry (PyGC-MS) was used as a rapid method for the characterization of permanent marker ink. Twenty-four samples of various colours purchased from different manufacturers were characterised. Four main typologies of polymer-binding medium could be distinguished on the basis of the pyrolysis products, and differentiation between permanent markers of different manufacturers could be accomplished. For some permanent marker samples, PyGC-MS analysis allowed pigment identification as well.

Characterizations of the colloidal and microbial organic matters with respect to membrane foulants

Nanofiltration has been studied and operated as an advanced water treatment process with respect to the removal of natural organic matter (NOM) and micropollutants throughout the world. However, fouling is an inherent phenomenon that reduces membrane performance, such as the flux and removal efficiency. In this study, filtration with a semi-pilot type of nanofiltration was conducted with coagulation/sedimentation treated water for the removal of NOM at a drinking water treatment plant in Korea. However, severe flux decline and reduction of removal efficiency were observed after 3 months. Tested membranes were autopsied using cleaning agents, including pure water and caustic solutions. The foulants eluted with the cleaning agents exhibited relatively high molecular weight (MW) distributions, as determined by a high performance size exclusion chromatography method, and also contained polysaccharide and/or protein-like substances identified from IR spectra analysis. To identify the compounds with high MW values, a dialysis membrane bag, with MWCO range from 12,000 to 14,000 Da, was used to isolate the colloidal NOM from raw surface water from the Dongbok Lake in Korea. The isolated compounds were compared to various organic compounds, including algogenic organic matter (AOM), bovine serum albumin, humic acids from the Suwanee River and soluble microbial products (SMP), in terms of their size, structure, IR analysis and pyrolysis gas chromatography–mass spectrometry analysis. The colloidal NOM was highly hydrophilic, as identified from XAD resin fractionation method. The organic foulants from the tested NF membranes, with high MW and hydrophilicity, and the saccharides and/or proteins-like substances (i.e., colloidal NOM) had similar characteristics to microbial by-products, such as SMP and AOM.

Pyrolysis-gas chromatography mass spectrometry analysis of starch-based ion-exchangers

The pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) analysis of ion-ex-changers prepared from starch by crosslinking with epichlorohydrin (E) in the presence of NaOH and water, with or without NH 4OH and 3-chloro-2-hydroxypropyltrimethyl-ammonium chloride (CHMAC) was performed. The data were compared with results run on polymers formed from E, NH 4OH and CHMAC in the absence of starch. The total ion chromatograms showed differences in the composition of degradation products. The pyrolysis of unmodified starch produced predominantly 2-furaldehyde, 3,5-dihydroxy-2-methyl-4H-pyran-4-one, 5-hydroxymethylfuraldehyde, 3-methoxy-5-methyl-2(5H)-furanone, 1,4-dideoxy- d-glycero-hex-1-en-pyranose-3-ulose, and levoglucosan. These products were formed to a much lower extent by pyrolysis of starch derivatives and were not formed from samples prepared in the absence of starch. However the chemical linkage of the poly(hydroxypropyl) matrix to starch or to the quaternary ammonium groups could not be proved by this method because none of the identified products had this type of linkage or indicates the linkage in analysed material. Only indirect proof of linkage can be concluded from the dramatic decrease of degradation products from starch in the modified starch samples.