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The detection of individual chromophores that contribute to the overall discoloration of paper ("yellowing") is a challenge because those substances are only present in very small amounts. In this research, two analytical approaches based on ambient ionization techniques, namely, desorption electrospray ionization and paper spray, both coupled to mass spectrometry, are compared to each other with regard to their suitability for detecting acetylated cellulosic key chromophores. The paper spray approach proved to be the more sensitive and versatile method. Subsequently, paper spray (PS)-mass spectrometry was applied to model papers and historical papers in which the acetylated chromophores were detected successfully. Independent accurate mass measurements confirmed the results obtained from reference compounds, model samples, and real-world specimens.

When a fire strikes libraries or archives, physical deterioration of the paper is so severe that its chemical properties are often regarded as less important. However, knowledge of the chemical changes of the papers upon nearly burning is necessary to design a subsequent conservation treatment. In the present study, we have examined a rag paper object, which partially survived a fire, and analysed its chemical properties by various methods. The polymeric state of cellulose, as well as its low-molar mass degradation products, were assessed. Comparison to an identical, unharmed duplicate provided a more profound understanding of the changes caused by the fire. Light scattering analysis revealed conformational changes of the cellulose molecule after high-temperature impact, and a chemical cross-linking was observed. In our study, we found the integrity of cellulose to depend on the temperature profile induced by the fire. The low thermal conductivity of cellulose protects the material even in close proximity to the burned edges.

The binding mechanisms of two reactive sizing agents, alkenyl succinic anhydride (ASA) and maleated sunflower oil high-oleic (MSOHO), with cellulose were studied. While ASA is produced from olefins out of fossil resources, MSOHO is a green sizing agent based on renewable plant materials. In contrast to common assumptions, that ASA is mostly covalently bound to cellulose, this study showed the largest part of ASA to be bound only by physisorption and only a rather small fraction, typically about 0.5 %, to be covalently attached by ester bonds. In the case of MSOHO, the covalent binding was only slightly higher, with about 3 % of the total amount being covalently linked. In both cases, covalently bound sizing agents were found to be almost uniformly distributed over the whole DP range of the cellulose as seen by carboxyl-selective fluorescence labeling in combination with size exclusion chromatography (“FDAM method”).

The acetylating action of ionic liquids frequently used in biomass and polysaccharide processing, namely 1,3-dialkylimidazolium acetates, on cellulose has been studied. Analysis was based on an accurate method to quantify even minute amounts of organic acetates in polysaccharides. The acetylation is caused by impurities in the ionic liquids, specially purified ionic liquids do not show an acetylating effect. 1-Acetylimidazole has been proven to be the actual acetylating agent, and its presence in aged ionic liquids has been confirmed. Formation of the reagent, mechanism of its action—being an acetyl transfer rather than a typical esterification—kinetics of the acetylation and the effect of water in the system are studied in detail. The implications on processing of biomaterials in ionic liquids are discussed as well.

A novel approach to measure the degree of acetylation in biopolymers applying a combination of Zemplen-deacetylation by sodium methanolate and GC-MS methodology is introduced. The development focuses on very low limits of detection to cover also samples with extremely low degrees of acetylation which hitherto eluded accurate determination. Free acetic acid or inorganic acetates, often present in biopolymer samples, do not disturb the quantification. Two techniques to measure the Zemplen-released methyl acetate were comparatively assessed, direct injection of the liquid phase and a SPME-based approach, the former being more straightforward, but being inferior to the latter in sensitivity. By applying isotopically labeled methyl acetate released from 4-O-(13C2-acetyl)-vanillin as the internal standard, influences, such as varying moisture contents, are corrected, improving the overall method reliability to a large extent. The combination of Zemplen-release of acetyl groups in biopolymers as methyl acetate, in connection with its accurate quantification by SPME-GC-MS, was found to be the method of choice for routine, yet very accurate analysis of a wide range of acetylation degrees of biopolymers, showing satisfying analytical parameters along with easy handling and widest applicability. Limit of detection for acetylated cellulose samples is 0.09nmol/mg, for hemicellulose samples 0.48nmol/mg.

Widening the methodology of chromophore analysis in pulp and paper science, a sensitive gas-chromatographic approach with electron-capture detection is presented and applied to model samples and real-world historic paper material. Trifluoroacetic anhydride was used for derivatization of the chromophore target compounds. The derivative formation was confirmed by NMR and accurate mass analysis. The method successfully detects and quantifies hydroxyquinones which are key chromophores in cellulosic matrices. The analytical figures of merit appeared to be in an acceptable range with an LOD down to approx. 60 ng/g for each key chromophore, which allows for their successful detection in historic sample material.

Degraded celluloses are becoming increasingly important as part of product streams coming from various biorefinery scenarios. Analysis of the molar mass distribution of such fractions is a challenge, since neither established methods for mono- or disaccharides nor common methods for polysaccharide characterization cover the intermediate oligomer range appropriately. Size exclusion chromatography (SEC) with multi-angle laser light scattering (MALLS), the standard approach for celluloses, suffers from decreased scattering intensities in the lower-molar mass range. The limitation in the low-molecular range can, in principle, be overcome by calibration, but calibration standards for such “short” celluloses are either not readily available or structurally remote and thus questionable. In this paper, we present the calibration of a SEC system— for the first time – with monodisperse cellooligomer standards up to about 3400 g mol −1 . These cellooligomers are “short-chain celluloses” and can be seen as the “true” standard compounds, by contrast to commonly used standards that are chemically different from cellulose, such as pullulan, dextran, polystyrene, or poly(methyl methacrylate). The calibration is compared against those commercial standards and correction factors are calculated. Calibrations with non-cellulose standards can now be adjusted to yield better fitting results, and data already available can be corrected retrospectively.

In the present work, a viable protocol was developed to prepare monodisperse cellooligomers up to a degree of polymerisation (DP) of 20. Peracetylated cellooligosaccharides were obtained from cellulose by acetolysis and subsequently purified by Normal Phase-High Performance Liquid Chromatography using toluene, ethyl acetate and acetone as eluents. In addition, we demonstrated how to efficiently monitor the purity and dispersity of the obtained compounds by High Performance Thin Layer Chromatography, Matrix-Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry and Nuclear Magnetic Resonance. With this approach, it is possible to isolate cellooligomer standards up to DP 20 on a preparative scale (dozens of mg). The column chromatographic separation proved to be robust over several months and to be scalable from a analytical to a preparative column. The isolated oligomer standards allow a more precise description of cellooligomer distributions typically emerging from biorefinery process streams after hydrolysis of lignocelluloses. They can be used to calibrate the oligomeric region in size-exclusion chromatography where light scattering detection fails due to limited scattering intensities.

This review provides a general overview of preparation, separation, and analytical methods for cello- and xylooligosaccharides. Arising as side-stream products of different biorefinery processes, these compounds have increasingly gained the interest of researchers and engineers in the last few decades. Beside their application as additives in the food, feed, and pharmaceutical industries, these oligomeric carbohydrates are of key importance as model compounds for studying the dependence of physicochemical properties on the degree of polymerization (DP). First, different preparation methods for mixtures of oligosaccharides with DPs between 1 and 30 are discussed. These methods include acetolysis, acid and enzymatic hydrolysis, and glycoside synthesis. Then, separation techniques, including size exclusion chromatography, normal phase and hydrophilic interaction chromatography, and chromatography on cation exchange resins, are presented. Analysis of oligosaccharides by different techniques is described.

Grasslands are often abandoned due to lack of profitability. Extensively cultivating grassland for utilization in a biogas-based biorefinery concept could mend this problem. Efficient bioconversion of this lignocellulosic biomass requires a pretreatment step. In this study the effect of different steam explosion conditions on hay digestibility have been investigated. Increasing severity in the pretreatment induced degradation of the hemicellulose, which at the same time led to the production of inhibitors and formation of pseudo-lignin. Enzymatic hydrolysis showed that the maximum glucose yields were obtained under pretreatment at 220 °C for 15 min, while higher xylose yields were obtained at 175 °C for 10 min. Pretreatment of hay by steam explosion enhanced 15.9% the methane yield in comparison to the untreated hay. Results indicate that hay can be effectively converted to methane after steam explosion pretreatment.