•Fucoidan from Cladosiphon okamuranus was purified for chemical structure elucidation.•The majors components of the fucoidan were fucose (70.13 ± 0.22 wt%) and sulphate (15.16 ± 1.17 wt%).•Fucoidan ...structure: →3)-α-fuc(1→0.52→3)-α-fuc-4-OSO3-(1→0.33→2)-α-fuc0.14.
Fucoidan is a sulphated polysaccharide, made up mainly of l-fucose, which is found in brown seaweeds. Its chemical structure is diverse and depends on maturity, species and geographical location. The objective of this study was to elucidate the chemical structure of fucoidan from Cladosiphon okamuranus harvested in Japan. The fucoidan was subject to purification prior to monosaccharide profiling, sulphate content determination, and linkage analysis. Our results showed that Japanese Cladosiphon okamuranus fucoidan contained 70.13 ± 0.22 wt% fucose and 15.16 ± 1.17 wt% sulphate. Other minor monosaccharides found were d-xylose, d-galactose, d-mannose, d-glucose, d-arabinose, d-rhamnose and d-glucuronic acid. Linkage analysis revealed that fucopyranoside units along the backbone are linked, through α-1,3-glycosidic bonds, with fucose branching at C-2, and one sulphate group at C-4 per every three fucose units, i.e. the structure of fucoidan from Japanese Cladosiphon okamuranus is →3)-α-fuc(1→0.52→3)-α-fuc-4-OSO3-(1→0.33→2)-α-fuc0.14.
A round robin on GPC of a wide range of different pulp samples was conducted among leading groups in cellulose analysis. The aim was to survey the status quo of the methods available to date. The ...pulp samples covered not only fully-bleached dissolving pulps but also bleached paper pulps and one unbleached sample. The methods applied were current state-of-the-art GPC with RI, MALLS, and viscosimetry detectors. Different dissolution protocols were compared as well. Following from the obtained results, more standardized protocols were proposed for approaches with different equipment (RI or MALLS/RI) and solvent systems (direct dissolution or derivatization). Major influencing factors, such as derivatization compared to direct solution, calibration versus light scattering and in-between lab variation, were discussed.
Million tons of cellulosic paper have been used for insulating coils in oil-filled electrical power transformers, thereby assuring the electricity supply for our societies. The high working ...temperatures in transformers constantly degrade paper insulators throughout their service life of up to 40 years. We approached the structural changes in oil-immersed cellulosic paper samples upon thermal stress in a study that compared unbleached softwood Kraft paper used as insulator paper with pure cotton cellulose paper. The model experiments used a thermal treatment in transformer oil at 170 °C for up to 14 days. The samples were characterized by means of
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C CP/MAS NMR spectroscopy, mainly based on deconvolution of the C4 resonance. An automated, fast, and reproducible C4 resonance deconvolution employing the “Peak Analyzer” tool of OriginPro 2020 (OriginLab Corporation, USA) was developed and used to exploit
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C CP/MAS NMR spectroscopy for the characterization of thermally stressed paper samples. Our results show that thermally induced structural changes depend heavily on the composition of paper, that hornification and coalescence of fibrils take place, and that the allomorph composition of cellulose crystallites is altered under the given conditions.
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•The effects of TEMPO-mediated oxidation were studied on lyocell fibers.•CHO and COOH profiles were analyzed in relation to the MWD of TEMPO-oxidized lyocell.•Significant decrease in the Mw was ...obtained during the first hour of TEMPO-oxidation.•COOH groups were introduced in the high molecular weight fractions.•The amount of functionalities can be controlled by selecting the oxidative conditions.
The effects of TEMPO-mediated oxidation, performed with NaClO, a catalytic amount of NaBr, and 2,2′,6,6′-tetramethylpiperidine-1-oxy radical (TEMPO), were studied on lyocell fibers by means of GPC using multiple detection and group-selective fluorescence labeling according to the CCOA and FDAM methodology. The applied method determines functional group content as a sum parameter, as well as functional group profiles in relation to the molecular weight of the cellulose fibers. Both the CHO and COOH profiles, as well as molecular weight alterations, were analyzed. A significant decrease in the average molecular weight was obtained during the first hour of TEMPO-mediated oxidation, but prolonged oxidation time resulted in no strong additional chain scission. Significant amounts of COOH groups were introduced in the high molecular weight fractions by the oxidation with higher concentrations of NaClO (2.42–9.67mmol NaClO/g fiber) after modification times of 1h or longer.
In this work, plasma pretreatment of raw cotton fibers combined with silver sorption was used for the preparation of antimicrobial fabrics. Special attention was given to the aging effect ...investigated seven days after plasma treatment. Raw cotton fabrics were modified with atmospheric pressure dielectric barrier discharge (DBD) in air, nitrogen, and oxygen. After plasma treatment, surface morphology and chemistry were characterized by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), respectively, molecular weight distribution and functional groups profile in cellulose were determined by GPC-MALLS with fluorescence labeling, while sorption properties were evaluated through wettability and moisture sorption measurements. Silver sorption was performed either immediately after treatment or seven days after plasma treatment, in order to investigate the aging effect on the sorption of Ag
+
. Antimicrobial activity was tested using agar diffusion test against S. aureus, E.coli, and C. albicans. Results have shown that silver sorption is improved and significantly higher when sorption is performed seven days after plasma treatment and consequently antimicrobial activity is also enhanced. This work confirms the significance of plasma aging in natural cellulose fibers' functionalization which presents yet another variable that should be taken into account when planning the procedure for fibers functionalization.
Ionic liquids with 1-alkyl-3-methyl-imidazolium cations react at C-2 with the reducing ends of cellulose forming a carbon–carbon bond, and are thus no inert cellulose solvents. The reaction is ...catalyzed by bases, such as commonly present impurities in ILs.
Ionic liquids with 1-alkyl-3-methyl-imidazolium cations react at C-2 with cellulose at its reducing end, forming a carbon–carbon bond. The reaction is strongly catalyzed by bases, such as the commonly present impurities in ILs, imidazole, and 1-methylimidazole. The direct reaction was verified by means of
13C-isotopical labeling and with the help of an IL that carried a fluorescence label which was transferred to cellulose upon the reaction. In solutions of cellulose in alkylmethylimidazolium ILs, both the ionic liquid and the cellulose are evidently not inert.
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•Stability of cotton during natural aging depends on the degree of TEMPO oxidation.•For high degree of oxidation, the molar mass is stable at level-off DP in aged cotton.•Low degree ...of oxidation leads to moderate degradation of molar mass in aged cotton.•The limiting values of tensile strength was obtained for aged TEMPO-oxidized cotton.
Stability of cotton fibers oxidized by the 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated system during natural aging was monitored; the oxidized and five-year-aged fibers were characterized in terms of molecular weight distribution, quantity and distribution of functionalities, tensile strength, color difference, and yellowness index. The distribution of functionalities introduced in cotton fibers by TEMPO-mediated oxidation and subsequent aging was investigated by means of gel permeation chromatography using multiple detection and group-selective labeling. The mild TEMPO-mediated oxidation retains the molar mass of oxidized cotton, but this status is not stable during natural aging. For highly oxidized cotton, the molar mass of aged fibers is low but stable. Aged TEMPO-oxidized cotton shows a prominent discoloration and an increased yellowness index. For tensile strength, the limiting value was obtained for aged TEMPO-oxidized cotton, regardless of whether the samples had initially been oxidized with a low or high degree of oxidation.
β-Irradiation (“e-beaming”) as well as swelling in ionic liquids, each process by itself, are common pretreatments in biorefinery scenarios. A combination of both, such as occurs with β-irradiation ...of biomass that was insufficiently washed and still contains traces of ionic liquids, causes covalent derivatization of the contained cellulose and incorporation of nitrogen. The nitrogen uptake occurred only in the presence of the ionic liquid and correlated linearly with both the irradiation dose and the concentration of the contained ionic liquid. The presence of other wood constituents during β-irradiation decreased nitrogen uptake, but did not prevent it. The derivatization of cellulose did not depend on the degree of crystallinity, but appeared to depend on the content of oxidized groups (carbonyl functionalities), also with a linear correlation. Future work must now clarify the mechanism of this reaction and the influence of other wood constituents, and address the possible potential of e-beaming in the presence of imidazolium ionic liquids for cellulose chemistry.
Wood extractives are known to cause problems during the production of pulp and paper and to impact their mechanical properties. In the present work, we systematically explored whether minute residual ...amounts of extractives that reprecipitate on the fiber surface in the final stages of the pulping process would lower the thermal resilience of softwood Kraft pulp. Pulp samples subjected to different extraction methods were characterized by means of thermogravimetric analysis. The compound classes constituting the respective extracts were identified and quantified via gas chromatography-mass spectrometry/flame ionization detector (GC-MS/FID) and the influence of the individual compound classes on the thermal stability of the samples was investigated separately. Soxhlet extraction with an ethanol/toluene solvent system clearly led to increased thermal stability. Besides fatty acids and resin acids also sterols and sterol esters that do not carry carboxylic acid functionalities contributed to the deterioration of the thermal pulp properties. Lateral order indices derived from Fourier transformed infrared spectra and crystallinity indices derived from solid-state
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C nuclear magnetic resonance spectra indicate that upon thermal degradation, the presence of even minute amounts of extractives leads to an increased degree of supramolecular disorder. Moreover, the characterization of the samples’ carbohydrate composition by means of acidic hydrolysis showed a tendency towards facilitated pyrolysis of the hemicelluloses if extractives were present in the pulp.
A novel method for the precise and accurate quantification of wood monosaccharides by gas-chromatography mass-spectrometry in complex lignocellulosic biomass matrices is presented. Instead of using ...the syn- or the anti-peak obtained by blocking the anomeric center using e.g. oximation, the sum of each syn- and anti-peak pair is used for quantification rendering the approach of the apparently constant syn- and anti-peak area ratio. Each wood monosaccharide syn- and anti-peak could essentially be distinguished upon O-ethoximation followed by trifluoroacetylation and separation on a 14% cyanopropyl/phenyl- 86% dimethylpoly-siloxane column. Additionally, internal standardization was carried out applying isotopically labeled compounds. Hence, the analytical figures of merit, such as precision and accuracy, could be substantially improved compared to standard gas-chromatography mass spectrometry as well as high-performance anion exchange chromatography (HPAEC) coupled to pulsed-amperometric detection (PAD).
The applicability of the novel gas-chromatography mass-spectrometry approach is demonstrated by analysis of five selected lignocellulosic biomass sample matrices typically occurring in a biorefinery scenario. Even in exceedingly complex sample matrices precise and accurate data are obtained according to the methodology presented.
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•The summarized area of each syn- and anti-peak pair is used for quantification.•Each lignocellulose-monosaccharide syn- and anti-peak is baseline separated.•Internal standardization is based on applying isotopically labeled compounds.•Precision and accuracy is substantially improved for biorefinery samples.
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