Presence of 5-hydroxyguaiacyl units as native lignin constituents in plants as seen by Py-GC/MS

The presence of 5-hydroxyguaiacyl moieties in the lignin from several plants has been assessed by Py-GC/MS. Different woody (eucalypt) and nonwoody (flax, hemp, kenaf, jute, sisal and abaca) angiosperms were selected for this study. The pyrolysis of whole fibers released lignin-derived products with p-hydroxyphenyl, guaiacyl and syringyl structures. Indeed, a series of compounds having a 5-hydroxyguaiacyl nuclei, including 3-methoxycatechol, 5-vinyl-3-methoxycatechol and 5-propenyl-3-methoxycatechol, were detected and identified in all samples, although in lower amounts than the normal guaiacyl or syringyl compounds. The analysis of the lignins isolated from the same plants also showed the same 3-methoxycatechol derivatives found after whole fiber pyrolysis. These compounds are supposed to arise from the pyrolysis of 5-hydroxyguaiacyl moieties, which are supposed to be native constituents of lignin in plants forming benzodioxane substructures.     

Improving Accessibility and Reactivity of Celluloses of Annual Plants for the Synthesis of Methylcellulose

Pretreatments (water-soaking, pre-mercerization, mercerization under a pressure of 15 bars and steam explosion) were used to improve the accessibilities and reactivities of celluloses of bleached flax, hemp, sisal, abaca and jute pulps for the synthesis of methylcellulose. Degrees of crystallinity were determined by X-ray Diffraction (XRD) spectra. The iodine adsorption accessibilities of pulps were low and accessible fractions ranged from 1.3 to 5.2%. Accessible fractions in amorphous cellulose were calculated in the 5–18% range. The accessibilities of these pulps were hemp pulp > flax pulp > sisal pulp > jute pulp > abaca pulp. Fourier Transform Infrared (FTIR) spectra showed that mean hydrogen bond strengths were weakened and relative crystallinity indexes were decreased by pretreatments. The accessibility and reactivity of the abaca pulp were improved by water soaking, mercerization under 15 bars pressure, steam explosion and preliminary mercerization, of which steam explosion and pre-mercerization were the best treatments. Species was the main factor for the accessibility and reactivity.     

Direct analysis of alkylphenols in Ginkgo biloba leaves by thermochemolysis–gas chromatography/mass spectrometry in the presence of tetramethylammonium hydroxide

Thermochemolysis–gas chromatography/mass spectrometry (GC/MS) in the presence of tetramethylammonium hydroxide (TMAH) was applied to the determination of alkylphenols in Ginkgo biloba leaves directly using a vertical microfurnace pyrolyzer. TMAH thermochemolysis–GC enabled the highly sensitive determination of alkylphenols including ginkgolic acids and ginkgols in G. biloba leaves as their methyl derivatives on the resulted pyrograms. On the basis of their peak areas, the contents of the alkylphenols in G. biloba leaf sample were rapidly and precisely determined without using any tedious and time-consuming pretreatment.     

Swelling and dissolution of cellulose,Part III: plant fibres in aqueous systems

Raw and refined flax, hemp, abaca, sisal, jute and ramie fibres are dipped into N-methylmorpholine N-oxide (NMMO)–water with various contents of water and into hydroxide sodium (NaOH)–water. The swelling and dissolution mechanisms of these plant fibres are similar to those observed for cotton and wood fibres. Disintegration into rod-like fragments, ballooning followed or not by dissolution and homogeneous swelling are all observed as for wood and cotton fibres, depending on the quality of the solvent. Balloons are not typical of wood and cotton and they seem to be present in all plant fibres. Another interesting result is that the helical feature seen on the balloon membrane is not related to the microfibrillar angle. Plant fibres are easier to dissolve than wood and cotton. This is not related to the molar mass of the cellulose chain. Raw plant fibres keeping most its non-cellulosic components do not show the formation of balloons. Patrick Navard is a Member of the European Polysaccharide Network of Excellence (EPNOE)     

Identifying acetylated lignin units in non-wood fibers using pyrolysis-gas chromatography/mass spectrometry

A series of non-wood plant fibers, namely kenaf, jute, sisal and abaca, have been analyzed upon pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) of the whole material. The pyrolysis products mainly arise from the carbohydrate and lignin moieties of the fibers. The lignin-derived phenols belonged to the p-hydroxyphenylpropanoid (H), guaiacylpropanoid (G) and syringylpropanoid (S) structures, and showed a high S/G ratio of between 2.0 and 5.4, the highest corresponding to kenaf. Among the lignin-derived phenols released, small amounts of sinapyl and coniferyl acetates (in both cis- and trans-forms) were identified for the first time upon Py-GC/MS of lignocellulosic materials. Acetylation of the sinapyl and coniferyl alcohols was at the gamma-position of the side chain. The release of these alcohols derived from intact acetylated lignin units upon pyrolysis seems to indicate that the native lignin in the fibers selected for this study is at least partially acetylated. Sinapyl (and coniferyl) acetates have recently been suggested to be authentic lignin precursors involved in the polymerization of lignin along with the normal sinapyl and coniferyl alcohols. Py-GC/MS will offer a convenient and rapid tool for analyzing naturally acetylated lignins, as well as to screen plant materials for the presence of acetylated units in lignin.     

聚乙烯吡咯烷酮修饰的CdS纳米晶：多元醇合成、表征和可见光活性

采用溶剂热法合成了具有不同晶粒尺寸的聚乙烯吡咯烷酮（PVP）修饰的CdS纳米晶,并运用XRD,N₂物理吸附,TEM,IR,UV-Vis等手段进行表征。结果表明,所制得的样品均为聚乙烯吡咯烷酮(PVP)修饰的CdS纳米晶;添加四甲基氢氧化铵(TMAH)有利于获得晶粒尺寸较小的CdS纳米晶;受纳米晶粒尺寸的影响,CdS纳米晶的吸收边发生蓝移且可见光催化活性明显提高。     

Use of an injection port for thermochemolysis–gas chromatography/mass spectrometry: Rapid profiling of biomaterials

A simple and direct approach was developed for thermochemolytic analysis of a wide range of biomolecules present in plant materials using an injection port of a gas chromatograph/mass spectrometer (GC/MS) and a novel solids injector consisting of a coiled stainless steel wire placed inside a modified needle syringe. Optimum thermochemolysis (or Thermally Assisted Hydrolysis/Methylation) was achieved by using a suitable methanolic solution of trimethylsulfonium hydroxide (TMSH) or tetramethylammonium hydroxide (TMAH) with an injection port temperature of 350 °C. Intact, methylated flavonoids, saccharides, phenolic and fatty acids, lignin dimers and diterpene resin acids were identified. Samples include tea leaves, hemicelluloses, lignin isolates and herbal medicines. Unexpected chromatographic results using TMAH reagent revealed the presence of intact methylated trisaccharides (658 Da) and structurally informative dimer lignin markers.     

树脂酸性组分的氢氧化四甲铵甲基化与GC-MS分析

利用氢氧化四甲铵(TMAH)对马尾松树脂(塔罗油)进行甲基化，并对其产物进行GC—MS分析；研究表明TMAH甲基化后进行GC—MS分析是测定树脂中酸性组分的一种快速有效的方法，但酸性组分中的脂肪酸要比树脂酸难于甲基化，因此为了确保甲基化反应完全，应适当延长甲基化反应时间。     

Reaction efficiency of organic alkalis with various classes of lipids during thermally assisted hydrolysis and methylation

Reaction efficiencies of two organic alkalis, tetramethylammonium hydroxide (TMAH) and trimethylsulfonium hydroxide (TMSH), with lipids during thermally assisted hydrolysis and methylation (THM) were examined focusing on (1) the types of lipids and (2) degree of unsaturation of fatty acid moieties. Different types of lipids such as triglycerides, phospholipids, free fatty acids and cholesteryl esters containing saturated, monounsaturated or polyunsaturated fatty acid (PUFA) residues were subjected to THM-gas chromatography (GC) in the presence of TMAH or TMSH. The obtained results revealed that the THM reaction using TMAH allowed almost quantitative methylation of saturated and monounsaturated fatty acid components independently of the classes of lipids. However, strong alkalinity of TMAH brought about isomerization and/or degradation of PUFA components. In contrast, the use of TMSH was effective to highly sensitive detection of PUFA as well as saturated and monounsaturated fatty acid components contained in triglycerides, phospholipids (phosphatidylcholines) and free fatty acids. On the other hand, TMSH was proved to react hardly with any kind of fatty acid residues in cholesteryl esters due to their steric hindrance.     

Compositional analysis of copoly (DL-lactic/glycolic acid) (PLGA) by pyrolysis-gas chromatography/mass spectrometry combined with one-step thermally assisted hydrolysis and methylation in the presence of tetramethylammonium hydroxide

Rapid and precise compositional analysis of copoly (DL-lactic/glycolic acid) (PLGA) was performed by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) combined with one-step hydrolysis and methylation in the presence of tetramethylammonium hydroxide (TMAH). Pyrolysis of PLGA with TMAH gave two characteristic products, derivatives of DL-lactic acid and glycolic acid, which directly reflect the average molar composition of PLGA. The analytical results for PLGA samples with various compositional ratios were in good agreement with those obtained by 1H-NMR spectrometry, and the precision was satisfactory.     

Preparation of nanocrystalline anatase TiO2 using basic sol-gel method

Nanocrystalline titanium dioxide particles with anatase structure and high thermal stability have been synthesized using the basic sol-gel method. The particle size and morphology were refined under hydrothermal conditions in the presence of different concentrations of tetramethylammonium hydroxide (TMAH) at 210°C and 230°C. XRD and TEM analysis showed that the TiO₂ particles obtained were homogeneous and monodispersive at low contents of TMAH. All intense peaks, clearly observed in the XRD patterns, were assigned to the anatase phase and no rutile phase was observed. At high contents of TMAH, nanoscale small (10–30 nm) and larger (>100 nm) TiO₂ particles were one-pot synthesized. The nanocrystalline TiO₂ particles synthesized by this method have good thermal stability. With the sintering temperature of up to 650°C, all the XRD peaks maintained good agreement with the anatase reference data.     

Quantification of organic acids in particulate matter by coupling of thermally assisted hydrolysis and methylation with thermodesorption-gas chromatography–mass spectrometry

A quantitative method for the determination of organic acids in atmospheric particles is developed. The method couples a derivatisation step (thermally assisted hydrolysis and methylation) and a Curie point pyrolyser as a thermal desorption technique and gas chromatography–mass spectrometry (CPP-GC–MS). Among the reagents tested (tetramethylammonium hydroxide (TMAH), tetramethylammonium acetate (TMAAc) and phenyltrimethylammonium hydroxide (TMPAH)), the best performance was found using TMAAc as a derivatisation reagent for the reaction time of 4 s at 510 °C as heating temperature. Calibration was performed for a series of fatty acids (FA), dicarboxylic acids (DCA) and terpenoic acids (TA) under these conditions. Coefficients of determination (R²) were between 0.94 and 0.98. Limits of detection (LOD) were in the nanogram-range between 0.1 and 3.6 ng. The method is applied on atmospheric particle samples to obtain the quantification reproducibility and quantification limits. Reproducibility was determined in terms of relative standard deviations (RSD) for ambient aerosol samples collected by a high-volume-sampler (HVS, RSD = 6–45%, n = 10) and a Berner impactor (BI, RSD = 5–34%, n = 10). Based on 24 h sampling time the developed method enables quantification of all three classes of acids for both sampling techniques. Calibration data and presented volume concentrations are compared with literature data. A comparison with an off-line methylation-GC–MS using BF₃ as a derivatisation reagent and capillary electrophoresis coupled mass spectrometry (CE-MS) showed a good agreement. Minimal sample preparation is the main advantage of the developed method. Depending on the sensitivity requirements the present method can be a fast and simple alternative to GC–MS techniques with conventional sample preparation steps for semi-volatile organic acids.     

Organophosphorus esters—IV : Novel approach to monoalkyl hydrogen phosphites

Tetramethylammonium t-butyl hydrogen phosphite (2), readily available from the reaction between di-t-butyl phosphite and aqueous tetramethylammonium hydroxide, was found to be a convenient phosphorylating agent for organic halides. It reacts easily with alkyl iodides and some alkyl bromides in boiling acetone affording the corresponding alkyl t-butyl phosphites (3). On treatment with trifluoroacetic acid at room temperature these compounds can be readily converted into monoalkyl hydrogen phosphites (1), isolated and characterized as S-p-chlorobenzylthiouronium derivatives (4).     

Structural and physico-chemical characterization of lignins solubilized during alkaline peroxide treatment of barley straw

In this paper, the seven acid-insoluble lignin preparations from barley straw were first extracted with alkaline hydrogen peroxide in order to study how the delignification and degradation of the lignin is influenced by aqueous 1.5% H₂O₂ extractant to straw ratios. The results showed that treatment of dewaxed barley straw with 1.5% H₂O₂ at 45°C for 14 h (pH 12.0) under the extractant to straw ratios of 10:1, 13:1, 15:1, 18:1, 20:1, 25:1, and 30:1 resulted in dissolution of 65.8%, 68.4%, 68.4%, 69.0%, 69.7%, 71.6%, and 72.3% of the original lignin and 78.7%, 79.8%, 82.3%, 83.4%, 84.8%, 85.3%, and 85.3% of the original hemicelluloses, respectively. The degraded seven lignin samples were analyzed with respect to their chemical compositions, content of chemically linked polysaccharides, molecular weights and structural changes. It was found that the alkaline peroxide treatment under the conditions given led to a noticeable increase in a amount of carboxyl groups due to the oxidation. The results from 13C-NMR analyses showed that the treatment was extremely effective for isolation of highly pure lignins from the straw, and the treatment under the conditions used did not affect the overall structure of lignin. The β-O-4 ether bond and β-β carbon-carbon linkage were found to be the major linkages between lignin units. Hydroxycinnamic acids, such as p-coumaric and ferulic acids, appeared to be strongly linked to lignin molecules, in which p-coumaric acid was found to be bonded to lignin by ester linkage, while ferulic acid was linked by its phenolic group via ether bond to lignin and also principally linked by its carboxyl group via ester bond to lignin and/or hemicelluloses.     

Degradative analysis of aquatic fulvic acid: CuO oxidation versus pyrolysis after tetramethylammonium hydroxide treatments in air and helium atmospheres

The structural composition of Nordic aquatic reference fulvic acid was investigated using chemical and thermal degradation methods: alkaline CuO oxidation and analytical pyrolysis after tetramethylammonium hydroxide (TMAH) pretreatment. Off-line procedures of the TMAH treatments were carried out under both air and helium atmospheres, with the aim of clarifying the effect of oxygen. Irrespective of the fact that the chemical and thermal degradation methods gave qualitatively quite similar basic products (mainly phenols and phenolic acids together with aromatic and aliphatic carboxylic acids), they also revealed their unique selectivity and efficiency for releasing different kinds of structural constituents. The results verify the formation of additional carboxyl functionality in the CuO oxidation. However, some similar oxidative reactions also appeared to take place during the pretreatment procedures of strongly basic TMAH, especially under an air atmosphere. The use of inert and protective atmosphere during the TMAH pretreatment is therefore recommended for producing more relevant structural information about the complex composition of humic substances.     

Characterisation of Siccative Oils, Resins and Pigments in Art Works by Thermochemolysis Coupled to Thermal Desorption and Pyrolysis GC and GC-MS

Thermal desorption in the presence of tetramethylammonium hydroxide (TMAH) has been applied to materials belonging to the artistic field to verify the effectiveness of the derivatisation reaction. Thermal desorption of siccative oils and abietane resins give consistent results with traditional pyrolysis in methylation conditions, while as regard antraquinonic dyes the milder thermal treatment leads to the formation of more diagnostic compounds than pyrolysis.     

Arsenic in marine tissues — The challenging problems to electrothermal and hydride generation atomic absorption spectrometry

Analytical problems in determination of arsenic in marine tissues are addressed. Procedures for the determination of total As in solubilized or extracted tissues with tetramethylammonium hydroxide and methanol have been elaborated. Several typical lyophilized tissues were used: NIST SRM 1566a ‘Oyster Tissue’, BCR-60 CRM ‘Trace Elements in an Aquatic Plant (Lagarosiphon major)’, BCR-627 ‘Forms of As in Tuna Fish Tissue’, IAEA-140/TM ‘Sea Plant Homogenate’, NRCC DOLT-1 ‘Dogfish Liver’ and two representatives of the Black Sea biota, Mediterranean mussel (Mytilus galloprovincialis) and Brown algae (Cystoseira barbata). Tissues (nominal 0.3 g) were extracted in tetramethylammonium hydroxide (TMAH) 1 ml of 25% m/v TMAH and 2 ml of water) or 5 ml of aqueous 80% v/v methanol (MeOH) in closed vessels in a microwave oven at 50 °C for 30 min. Arsenic in solubilized or extracted tissues was determined by electrothermal atomic absorption spectrometry (ETAAS) after appropriate dilution (nominally to 25 ml, with further dilution as required) under optimal instrumental parameters (pyrolysis temperature 900 °C and atomization temperature 2100 °C) with 1.5 μg Pd as modifier on Zr–Ir treated platform. Platforms have been pre-treated with 2.7 μmol of zirconium and then with 0.10 μmol of iridium which served as a permanent chemical modifier in direct ETAAS measurements and as an efficient hydride sequestration medium in flow injection hydride generation (FI-HG)–ETAAS. TMAH and methanol extract 96–108% and 51–100% of As from CRMs. Various calibration approaches have been considered and critically evaluated. The effect of species-dependent slope of calibration graph or standard additions plot for total As determination in a sample comprising of several individual As species with different ETAAS behavior has been considered as a kind of ‘intrinsic element speciation interference’ that cannot be completely overcome by standard additions technique. Calibration by means of CRMs has given only semi-quantitative results. The limits of detection (3σ) were in the range 0.5–1.2 mg kg^− 1 As dry weight (wt.) for direct ETAAS analysis of extracts in both TMAH and MeOH. Within-run precision (RSD%) was 5–15% and 7–20% for TMAH and MeOH extracts at As levels 4–50 mg kg^− 1 dry wt., respectively.     

Content of Phenolic Compounds in Meadow Vegetation and Soil Depending on the Isolation Method

The aim of this paper was to determine the effect of the hydrolysis method on the amounts of phenolic compounds in the plant material in soil and, as a consequence, on the parameters to determine the degree of lignins transformation in soils. The study included the plant material (hay, sward, and roots) and soil—Albic Brunic Arenosol (horizon A, AE, and Bsv) samples. Phenolic compounds were isolated at two stages by applying acid hydrolysis followed by alkaline re-hydrolysis. The quantitative and qualitative analysis of phenolic compounds was performed with high-performance liquid chromatography with a DAD. The content of phenolic compounds in the extracts depended on the hydrolysis method and it was determined by the type of the research material. The amounts of phenolic compounds contained in the alkaline hydrolysates accounted for 55.7% (soil, horizon Bsv)—454% (roots) of their content in acid hydrolysates. In the extracts from acid hydrolysates, chlorogenic and p-hydroxybenzoic acids were dominant. In the alkaline extracts from the plant material, the highest content was recorded for p-coumaric and ferulic acids, and in the extracts from soil, ferulic and chlorogenic acids. A combination of acid and alkaline hydrolysis ensures the best extraction efficiency of insoluble-bound forms of polyphenols from plant and soil material.     

Repeatability and pattern recognition of bacterial fatty acid profiles generated by direct mass spectrometric analysis of in situ thermal hydrolysis/methylation of whole cells

Direct CI mass spectrometry profiling of fatty acid methyl esters (FAMEs) from in situ thermal hydrolysis/methylation (THM) of whole bacterial cells with tetramethylammonium hydroxide (TMAH) has been demonstrated as a potential method for real time and fieldable detection/identification of microorganisms. Bacillus anthracis (Ames), Yersinia pestis (Nair. Kenya), Vibrio cholerae (E1 Tor), Brucella melitensis (Abortus wild) and Francisella tularensis (LVS vaccine) were profiled by this method during a 10-month period. Repeatability of the in situ FAME data was calculated using one-way analysis of variance (ANOVA) and a t-test. Artificial neural network (ANN) and multivariate statistics of the FAME profiles were also compared for bacterial identification/classification. Equivalent results were obtained with a multivariate rule building expert system (MuRES) and the ANN. However, the ANN analysis required much less computer time and was deemed the best choice for this application. In situ THM FAME profiles of the bacterial samples provided comparable results with those obtained from the Microbial Identification System (MIDI) (Newark, DE) wet chemistry-gas chromatographic based system.     

Homogenization of food samples for gamma spectrometry using tetramethylammonium hydroxide and enzymatic digestion

Journal of Radioanalytical and Nuclear Chemistry - We have developed a method of food sample preparation for gamma spectrometry involving the use of tetramethylammonium hydroxide (TMAH) and/or...