Methylation-gas Chromatography-mass Spectrometry Research Articles

Effective pretreatment for thermally-assisted hydrolysis and methylation GC-MS of intractably cross-linked acrylate copolymers

Thermally-assisted hydrolysis and methylation-gas chromatography-mass spectrometry (THM-GC-MS) using tetramethylammonium hydroxide (TMAH) is an effective approach for the characterization of condensation polymers with ester linkages such as ultraviolet (UV)-cured acrylate resins. However, for intractably cured acrylic resins, reliable structural characterization is often difficult by conventional THM-GC-MS owing to insufficient THM reactions. In this study, a pretreatment to effectively improve THM efficiency was proposed, in which the resin sample was preliminarily soaked and dissolved in a TMAH-methanol solution in a microtube. An aliquot of the TMAH solution was then introduced into the pyrolyzer at 400 °C to produce THM-GC-MS. The effectiveness of the proposed pretreatment was demonstrated using a UV-cured acrylate copolymer consisting of bulky and high-molecular weight bifunctional acrylate (9,9-Bis[4-(2-acryloyloxy ethoxy) phenyl]fluorene) and monofunctional acylate (2-(9 H-Carbazol-9-yl)ethyl acrylate) monomers, for which THM reactions did not proceed efficiently in conventional THM-GC-MS. Conversely, by the modified THM-GC-MS process with a pretreatment involving immersion at room temperature for 24 h or at 60 °C for 30 min, the characteristic decomposition products for each monomer unit were clearly observed in the chromatograms, and the copolymer composition could be precisely estimated from the relative yields of the observed decomposition products. In addition, a methyl acrylate peak, formed from unreacted acrylate moieties in the photocured copolymer, appeared in the chromatogram. Its relative yields were correlated to the double bond conversion in the cured sample. The observed results were successfully interpreted to clarify the curing process of the photocured acrylate copolymer samples.

Exploration of changes in the chemical composition of sedimentary organic matter and the underlying processes during biodegradation through advanced analytical techniques

Environmental context Organic matter (OM) biodegradation plays a key role as it is one of the main processes causing changes in the amount, composition and properties of OM in sediment. However, a complete understanding of its processes and mechanisms is still not reached. In this study, we aim to explore the chemical composition changes during biodegradation and identify underlying processes. Rationale Although the scientific community has widely investigated organic matter biodegradation processes, only a limited number of studies have explored the molecular changes of this material, whereas its structure, composition and origin play a key role in these processes. Methodology We decided to examine the effects of biodegradation on the chemical composition of sedimentary organic matter and to explore the underlying mechanisms. We conceived a laboratory-based degradation experiment utilising organic-rich sediments artificially composed of two contrasting organic matter end-members (i.e. soil and algae) under two oxygen conditions. The sediment samples before and after incubation were then analysed by laser desorption ionisation–Fourier-transform–ion cyclotron resonance–mass spectrometry for molecular characterisation and by thermally assisted hydrolysis and methylation gas chromatography–mass spectrometry in order to offer insights into the mechanisms driving the biodegradation processes. Results Our results from molecular characterisation unveiled distinct pathways of biodegradation contingent upon the source material. Moreover, they hinted at a predilection for altering high molecular weight compounds like lignin & carboxylic-rich alicyclic molecules (CRAM) and condensed aromatic structures (CAS), manifesting as a conversion into lower molecular weight counterparts. Furthermore, the complementary findings from biomarker analyses underscored the influence of environmental factors – specifically oxygen conditions and microbial communities – on organic matter decomposition. Discussion Although this study is a controlled laboratory experiment and more studies are needed, it demonstrates the intricate interplay among chemical, biological and environmental factors that profoundly shape the reactivity of organic matter. This study underscores the critical need for persistent inquiry, aimed at unravelling the factors and conditions governing the diverse pathways of biodegradation.

Preparation, structural analysis, antioxidant and digestive enzymes inhibitory activities of polysaccharides from Thymus quinquecostatus Celak. leaves

In this study, polysaccharides (DJPs) were obtained from Thymus quinquecostatus Celak. leaves, which were DJP (the crude polysaccharide extracted by hot water), DJP30, DJP50, DJP70 (three polysaccharide fractions obtained by graded precipitation with final ethanol concentrations of 30%, 50%, and 70%), and DJP70-1 (a purified polysaccharide isolated from DJP70 by DEAE-52 cellulose column). DJPs were all high-molecular-weight heteropolysaccharides, with different contents of total carbohydrate, protein, uronic acid, and phenols. They were mainly composed of arabinose, galactose, glucose, galacturonic acid, and rhamnose, and DJP70-1 also surprisingly contained a higher proportion of mannose (Man). Structural characteristics were determined using infrared spectrum (IR), methylation-gas chromatography-mass spectrometry (GC-MS), and 1D/2D nuclear magnetic resonance (NMR) analysis, with the existence of 14 kinds of glycosyl linkages of DJP70-1. Morphological features of DJP70-1 determined by Congo red and scanning electron microscopy (SEM) were also significantly different from other DJPs. Moreover, these polysaccharides exhibited strong scavenging effects on 2, 2′-diphenyl-1-picrylhydrazyl (DPPH) and 2, 2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals, though the relatively weak scavenging effect on hydroxyl free radicals in vitro. Furthermore, the crude polysaccharide DJP exerted a protective effect against 2, 2′-azo-bis-(2-methylpropylimid)-dihydrochloride (AAPH)-induced oxidative stress in the zebrafish model by directly scavenging excessive reactive oxygen species (ROS) and activating the kelch-like ECH-associated protein 1 (KEAP1) - nuclear factor erythroid 2-related factor 2 (NRF2)/antioxidant response element (ARE) signaling pathway in vivo. α-amylase and α-glucosidase inhibitory activities evaluation results showed that DJPs were also good potential hypoglycemic agents.

An Investigation of Eighteenth-Century English Red Japanned Furniture in the Collection of The Metropolitan Museum of Art, New York

ABSTRACTThe decorative surfaces of four pieces of eighteenth-century English red japanned furniture, including a card table and side chair by Giles Grendey (1693–1780), were examined. Cross-sectional microscopy, X-ray fluorescence spectroscopy (XRF), Fourier transform infrared micro-spectroscopy (micro-FTIR), attenuated total reflectance micro-FTIR (micro-ATR-FTIR), Raman spectroscopy, thermally assisted hydrolysis and methylation-gas chromatography-mass spectrometry (THM-GC-MS) analysis, and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS) were used to investigate the layer structure and material use. Analysis revealed the common use of a spirit varnish based on sandarac and turpentine, whose simple formulation is at odds with those typically suggested in period recipes for red japanning. Vermilion pigment was used for the red grounds, but different preparatory layers as well as materials for relief decoration separate Grendey’s red furniture from the other objects studied. More examples need to be examined in order to ascertain whether observations regarding process and material use reflect wider practice. However, results from this preliminary investigation suggest that japanners in England were less reliant on the recipes of the treatises than has been supposed, as well as hinting at the possibility of identifying idiosyncratic practices of particular craftsmen.

Characterization of high-molar-mass fractions in a Scots pine (Pinus sylvestris L.) knotwood ethanol extract

AbstractThe identification of compounds in Scots pine (Pinus sylvestrisL.) knotwood (KnW), obtained by extracting with hydrophilic organic solvents, has been performed previously almost exclusively by gas chromatography-mass spectrometry (GS-MS) equipped with long GC columns (≥25 m). That means that the molar mass (MM) of the majority of the identified compounds was below 500–600 Da, and the analytical data accounted for only about half of the dry extract weight. In the present work, high-molar-mass (HMM) fractions in a Scots pine KnW-EtOH extract were isolated and chemically characterized by means of several advanced analytical techniques, such as high performance size-exclusion chromatography-evaporative light scattering detector (HPSEC-ELSD), high performance liquid chromatography (HPLC)-electrospray ionization-ion trap-mass spectrometry [(HPLC)ESI-IT-MS], ESI-quadrupole time of flight-mass spectrometry (QTOF-MS), pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), thermally assisted hydrolysis and methylation-gas chromatography-mass spectrometry (THM-GC-MS), nuclear magnetic resonance (NMR) and GC-MS. The results indicate that the MM maxima of the HMM fractions ranged from approximately 500 to 2200 Da, and that the compounds consist mainly of oligomers of hydroxylated resin acids (RAs), especially dehydroabietic acid, but also of fatty acids (FAs), stilbenes and sterols. A large number of RA dimers were tentatively identified in the HMM fractions. However, it remains unknown how the monomer units are linked together, as it was not possible to isolate a RA dimer fraction pure enough for NMR characterization. RA dimers in native KnW have not been identified previously.

Highlighting the wide variability in arsenic speciation in wetlands: A new insight into the control of the behavior of arsenic

Although the behavior of Arsenic (As) under reducing conditions in periods of high water levels in wetlands is well understood and documented, there is a lack of information under oxidizing conditions when the water level decreases. In this study, we were interested in the first stage of the oxidizing period, when oxidation products are still in suspension. A soil sample from the Naizin Kervidy wetland (France) was incubated in the laboratory to produce a reduced soil solution. The reduced solution was subsequently oxidized, filtered and ultrafiltered using decreasing pore size membranes (5μm, 3μm, 0.2μm, 30kDa and 5kDa). The distribution of As and Fe was investigated in each size fraction of the oxidized solution and their speciations were studied using XAS, HPLC and SEC-ICP-MS. Organic matter was characterized using thermally assisted hydrolysis and methylation gas chromatography–mass spectrometry (THM-GC–MS) and fluorescence spectroscopy. The majority of the As was present as As(V) but a small amount of As(III) still remained despite the advanced oxidized conditions. In the >0.2μm fractions, the XAS analyses showed that As was associated, in the second shell, with Fe (As–Fe=3.35Å) as bidentate binuclear complexes and C (As–C=2.90Å), suggesting the integration of As in biological objects. In the <30kDa fraction, As was directly bound to C (As–C=1.96Å) in the first shell indicating the presence of organic As species. In the second shell, an As–Fe distance of 3.35Å was found showing that part of the As was still complexed with Fe. The 0.2μm–30kDa fraction was a transitional fraction in terms of the Fe species and OM composition. In this fraction, organic matter exhibited a more humic character (aromatic molecules) inducing an increasing cation binding capacity. As a consequence, in this fraction and in the smallest one, As, Fe and OM seemed to form ternary complexes in which the Fe or nano-oxides in the >30kDa fraction and as monomer, or cluster in <30kDa fraction acted as a bridge. In all of the fractions, a proportion of As(V) was present as organic methylated species. These organic species might be produced by several organisms (animal or plant) via a detoxification process. They seemed to be bound to the particulate and colloidal Fe/OM phases as well as integrated in the remains of the organisms. Mass calculations provided evidence that 90% of the As was contained in the >5μm particulate fraction and thus was hardly mobile. This study showed that although wetlands have been identified as a potential source of As, a number of biological and geochemical trapping mechanisms also favor As stabilization in wetlands.

Analytical study of modern paint layers on metal knight shields: The use and effect of Titanium white

Painted metal knight shields of the Order of the Elephant produced during the last part of the 20th century are characterized by a striking variety in their conservation state. Three different coat systems were identified and investigated by Fourier transform infrared microscopy (μ-FTIR), micro-Raman spectroscopy (MRS), scanning electron microscopy–Energy dispersive X-ray spectroscopy (SEM–EDX) and Thermally assisted hydrolysis and methylation-gas chromatography–mass Spectrometry (THM–GC–MS). Chalking of the white paint layer on the first group of knight shields displayed in the window niches was found to be related to the use of titanium white of the anatase type. A pristine condition of the second group could be attributed to priming of the lead rich metal support with a zinc potassium chromate based primer and the use of mainly stable white pigments in the top coat. Severe delamination of the paint layer of the third group was caused by the formation of lead corrosion products between the paint layer and the metal support. The results are discussed in relation to the climatic conditions as well as the historical context of contemporary paint production and availability in Denmark.

Validation of Biomarkers for Distinguishing Mycobacterium tuberculosis from Non-Tuberculous Mycobacteria Using Gas Chromatography−Mass Spectrometry and Chemometrics

Tuberculosis (TB) remains a major international health problem. Rapid differentiation of Mycobacterium tuberculosis complex (MTB) from non-tuberculous mycobacteria (NTM) is critical for decisions regarding patient management and choice of therapeutic regimen. Recently we developed a 20-compound model to distinguish between MTB and NTM. It is based on thermally assisted hydrolysis and methylation gas chromatography-mass spectrometry and partial least square discriminant analysis. Here we report the validation of this model with two independent sample sets, one consisting of 39 MTB and 17 NTM isolates from the Netherlands, the other comprising 103 isolates (91 MTB and 12 NTM) from Stellenbosch, Cape Town, South Africa. All the MTB strains in the 56 Dutch samples were correctly identified and the model had a sensitivity of 100% and a specificity of 94%. For the South African samples the model had a sensitivity of 88% and specificity of 100%. Based on our model, we have developed a new decision-tree that allows the differentiation of MTB from NTM with 100% accuracy. Encouraged by these findings we will proceed with the development of a simple, rapid, affordable, high-throughput test to identify MTB directly in sputum.

The identification of biomarkers differentiating Mycobacterium tuberculosis and non-tuberculous mycobacteria via thermally assisted hydrolysis and methylation gas chromatography–mass spectrometry and chemometrics

Infections with non-tuberculous mycobacteria (NTM) are increasing, particularly among immune-compromised patients and those with damaged lungs. Mycobacterium tuberculosis complex (MTB) strains, however, remain the most common cause of mycobacterial infection. A rapid method of distinguishing MTB from NTM is required for correct diagnosis and tuberculosis management. We have developed an automated procedure based on thermally-assisted hydrolysis and methylation followed by gas chromatography–mass spectrometry (THM–GC–MS) and advanced chemometrics to differentiate MTB from NTM. We used early cultures of mycobacteria in this first step towards the direct identification of these bacteria in sputum using a hand-held portable device. To build a classification model, we used 44 strains including 15 MTB and 29 NTM. A matrix of the aligned dataset containing ~45,700 features (retention time/mass pairs) for the 44 observations was submitted to partial least squares discriminant analysis (PLS–DA). We could reduce the number of features down to 250 without compromising the accuracy of the model. Twenty different compounds were found through mass spectral interpretation of these 250 features. Some of these compounds have not been linked to tuberculosis before, others have been proposed previously as diagnostic biomarkers for this disease. We have built a final model based on our proposed biomarkers that performed with 95 % accuracy in distinguishing MTB from NTM in early cultures. Since all these biomarkers have been chemically identified, work can proceed towards the development of simpler, bed-side diagnostic tests to differentiate MTB from NTM in sputum.

Changes in the Quality of Chromophoric Dissolved Organic Matter Leached from Senescent Leaf Litter during the Early Decomposition

Chromophoric dissolved organic matter (CDOM) leached from leaf litter is a major source of humus in mineral soil of forest ecosystems. While their functions and refractoriness depend on the physicochemical structure, there is little information on the quality of CDOM, especially for that leached in the very early stages of litter decomposition when a large amount of dissolved organic matter (DOM) is leached. This study aimed to better understand the variations/changes in the composition of CDOM leached from senescent leaf litter from two tree species during the early stage of decomposition. Leaf litter from a conifer tree (Japanese cedar, D. Don) and a deciduous broad-leaved tree (Konara oak, Thunb.) were incubated in columns using simulated rainfall events periodically for a total of 300 d at 20°C. The quality of CDOM was investigated based on the fluorescence properties by using a combination of excitation-emission matrix fluorescence (EEM) and parallel factor analysis (PARAFAC). In addition, the phenolic composition of DOM was investigated at a molecular level by thermally assisted hydrolysis and methylation-gas chromatography-mass spectrometry (THM-GC-MS) in the presence of tetramethylammonium hydroxide (TMAH). The EEM was statistically decomposed into eight fluorescence components (two tannin/peptide-like peaks, one protein-like peak, and five humic-like peaks). A significant contribution of tannin/peptide-like peaks was observed at the beginning of incubation, but these peaks decreased quickly and humic-like peaks increased within 1 mo of incubation. The composition of humic-like peaks was different between tree species and changed over the incubation period. Since tannin-derived phenolic compounds were detected in the DOM collected after 254 d of incubation on THM-GC-MS, it was suggested that tannins partially changed its structure, forming various humic-like peaks during the early decomposition.

A multi-analytical approach for the identification of aloe as a colorant in oil–resin varnishes

Aloe plants have been widely documented in artists' treatises dating from the sixteenth to the nineteenth century as a source of colorant to achieve lustrous golden glazes on tin- and silver-foiled objects and warm-toned finishes on musical instruments, such as violins. Aloe extracts contain characteristic anthraquinone and phenolic components which impart a distinctive orange tone and fluorescence to mixtures containing them. Because of the low concentration of colorant in the coatings and its probable degradation by high temperature during manufacture, the identification of aloe in heated oil-resin mixtures represents an analytical challenge. For this reason, the possible presence of aloe in glazes and coatings has been largely overlooked. This paper describes various analytical approaches to the identification of aloe in historic samples, from comparison with results obtained from reference standards and mock-up samples. Complementary analytical techniques including thermally assisted hydrolysis and methylation-gas chromatography-mass spectrometry, high-performance liquid chromatography, laser desorption-mass spectrometry, matrix-assisted laser desorption-ionization-mass spectrometry and surface-enhanced Raman scattering were used. Different chemical markers were identified by the individual methods and the advantages and limitations of each technique for the identification of aloe in oil-resin varnishes are discussed.

Evaluation of comprehensive on‐line liquid chromatography thermally assisted hydrolysis and methylation–gas chromatography–mass spectrometry for characterization of sulfonated lignins

Sulfonated lignins, used as dispersants in agrochemical formulations, have been characterized by hyphenation of ion-pair RPLC and thermally assisted hydrolysis and methylation-GC-MC (THM-GC-MS). The chemical structure of a series of selected lignins was evaluated, both in terms of overall composition and in terms of composition as a function of molecular size. Some sulfonated lignins give rise to unstable formulations. In the compositional analysis, these samples were found to yield additional fragments. A newly developed comprehensive method made it possible to monitor the occurrence of these fragments as a function of molecular size. In addition to differences in the molecular size between "good" and "bad" batches, clear differences in chemical composition were established.

Analytical Study of a Resinous Material Used as Sealing in Ancient Pottery Found in an Archaeological Site by Thermally Assisted Hydrolysis Methylation–Gas Chromatography–Mass Spectrometry, Vibrational Spectroscopy and Light Microscopy

A resin sample was found in the archaeological site of Lixus (Morocco), belonging to the second century BC. The resinous material was found inside an amphora containing iron remains used in the plug as sealing material to hermetically close the pottery. The resinous sample was studied by several analytical techniques, as thermally assisted hydrolysis and methylation–gas chromatography–mass spectrometry (THM–GC–MS), Fourier transformed infrared spectroscopy (FTIR), and light microscopy. The material was identified as a Pinaceae resin. Therefore, a modern pine resin was also analyzed to consider the influence of aging in the archaeological sample. The ancient material was found not too oxidized, owing to the conservation conditions inside the amphora, protected from air and moisture.

Diel and seasonal variations in the chemical composition of biomass burning aerosol

Abstract. Fine aerosol particles were collected separately during daytime and nighttime at a tropical pasture site in Rondônia, Brazil, during the burning and dry-to-wet transition period in 2002. Total carbon (TC) and water-soluble organic carbon (WSOC) were measured by evolved gas analysis (EGA). Based on the thermochemical properties of the fine aerosol, the relative amounts of the volatile and refractory compounds were estimated. It was found that the thermally refractory (possibly higher molecular weight) compounds dominated the TC composition. Their contribution to TC was higher in the daytime than in the nighttime samples. The relative share of WSOC also showed a statistically significant diel variation as did its refractory fraction. Anhydrosugars and phenolic acids were determined by GC-MS and their diel variation was studied. Based on the decrease of their relative concentrations between the biomass burning and transition periods and their distinctly different diel variations, we suggest that the phenolic acids may undergo chemical transformations in the aerosol phase, possibly towards more refractory compounds (humic-like substances, HULIS), as has been suggested previously. These conclusions are supported by the results of the thermally assisted hydrolysis and methylation gas chromatography-mass spectrometry of the same filter samples.

THM-GCMS and FTIR for the investigation of paints in Picasso's Still Life, Weeping Woman and Nude Woman in a Red Armchair from the Tate Collection, London

Thermally assisted hydrolysis and methylation-gas chromatography–mass spectrometry (THM-GCMS) in conjunction with Fourier transform infrared spectroscopy (FTIR) have been successfully used for the identification of different binding media, including synthetic resins and natural binders, employed by Picasso on Still Life (1914), Nude Woman in a Red Armchair (1932) and Weeping Woman (1937), works owned by the Tate, London. In particular, the results obtained prove that at certain dates Picasso experimented and likely mixed his oil paints with other compounds, such as animal fats, and at very early date he employed alkyd resins, unusual for the times.

Characterization of thermally assisted hydrolysis and methylation products of polyphenols from modern and archaeological vine derivatives using gas chromatography–mass spectrometry

If some ceramics, such as vinary amphorae attest the consumption and trade of wine in the Roman world, the first wine productions in Occident often stay undocumented. Chemical analysis of organic materials preserved in archaeological vessels is the only way to bring new lights about the elaboration and the consumption of this fermented beverage. To determine the preservation state of wine and other grape derivatives residues, we proceeded to in situ tetramethylammonium hydroxide (TMAH) treatment followed by thermally assisted hydrolysis and methylation—gas chromatography—mass spectrometry (THM–GC–MS). The objectives of the study were (i) the understanding of the pyrolytic mechanisms of proanthocyanidins and (ii) the assessment of the usefulness of thermochemolysis for the identification of phenolic markers from polymeric solid deposit in modern wine bottle and Roman amphorae. THM–GC–MS was revealed to be an efficient method for the characterization of fruit derivatives even if mixed with another organic material, such as pitch used to ensure the watertightness of the ceramic container. The preservation of tannins during millennia in archaeological context is here enlightened for the first time by using analytical pyrolysis. The proposed identification of vinary residues is now based on the detection of the association of more than 30 pyrolytic markers derived from di- and trimethoxylated benzenoid compounds. THM–GC–MS represents a new method for the rapid detection of wine traces in ancient ceramics, adapted to tiny samples (<0.1 mg), allowing to precise the role and function of pottery during antiquity.

THM-GCMS and FTIR for the study of binding media in Yellow Islands by Jackson Pollock and Break Point by Fiona Banner

Throughout the 20th century a number of binding media, including synthetic resins, have been employed in paints. It is only very recently that thermally assisted hydrolysis and methylation-gas chromatography-mass spectrometry (THM-GCMS) has been used for the identification of a wide variety of binding media employed in the 20th century art. This paper shows as THM-GCMS was successfully used in conjunction with Fourier Transform Infrared Spectroscopy for the study of binding media in samples from Yellow Islands by Jackson Pollock [Tate Collection, T00436] and Break Point by Fiona Banner [Tate Collection, T07501].

Ageing behaviour and pyrolytic characterisation of diterpenic resins used as art materials: colophony and Venice turpentine

The ageing behaviour of two diterpenic resins traditionally used as artists’ materials, colophony and Venice turpentine, was investigated with different spectroscopic and chromatographic techniques. In particular, three types of ageing (natural, artificial external conditions with a xenon lamp, artificial indoor conditions with fluorescent tubes) were applied to laboratory samples to study their effects on chemical structures. Thermally-assisted hydrolysis and methylation-gas chromatography-mass spectrometry (THM-GC/MS) was employed for careful characterisation and for identification of markers compounds on the vergin resins and in the course of ageing. The most significant changes were detected in the initial part of ageing, and the principal degradation products coming from oxidation, polymerisation and cleavage reactions identified. The high intensity of xenon lamp irradiation was found to cause, apart from oxidation and polymerisation reactions, further degradation of the chemical structure with molecular fragmentation. From the analytical point of view, the differentiation between colophony and Venice turpentine with THM-GC/MS appears to depend on differences in the lower molecular weight resin components.

Characterization of humic substances in highly polluted river sediments by pyrolysis methylation–gas chromatography–mass spectrometry

Humic substances were extracted from two sediment cores sampled in a river on the outskirts of a large city (Deûle near Lille, France) and in its highly polluted oxbow-lake. Humic acids (HA) were characterized by infrared spectroscopy and in situ pyrolysis/methylation–gas chromatography–mass spectrometry. The main results are the substantial aliphaticity of HA in the oxbow-lake at all depths, mainly due to the presence of a lipid fraction associated with the HA structure. The abundance of sterols in this fraction implies that lipids could originate from the accumulation of sewage in the oxbow-lake. Humic acids of the Deûle sediments show a different trend ; their evolution is characterized by a decrease of the pollutant inputs with increasing depth. The results demonstrate the efficiency of Py–GC–MS in identifying the different organic contributions to HA and in distinguishing natural from anthropogenic sources.

Pyrolysis mass spectrometry and pyrolysis gas chromatography-mass spectrometry of ester- and ether-linked phenolic acids in coastal bermudagrass cell walls

Coastal bermudagrass cell walls were treated with 2 M NaOH at room temperature and subsequently with 4 M NaOH at 170° to determine the amounts of esterified and etherified phenolic acids, respectively. In addition, total phenolic acids were determined by direct treatment of the cell walls with the 4 M treatment. Treatment with 2 M NaOH removed ester-linked p-coumaric, ferulic, truxillic and truxinic acids. Further treatment of the cell wall residue with 4 M NaOH at elevated temperature removed ether-linked phenolic acids. Pyrolytic methylation gas chromatography-mass spectrometry of the residue after 2 M NaOH treatment showed the presence of a small amount of ether-linked truxillic and truxinic acids. Data from the sequential sodium hydroxide and direct 4 M sodium hydroxide treatments showed that a total of 13.3% of the p-coumaric acid and 45.4% of the ferulic acid was ether-linked. A substantial portion of these ether-linked acids was present as a base-soluble fraction of the 2 M treatment.