The qualitative and quantitative analysis of complex carbohydrate mixtures is a challenging problem. When tackled by GC/MS, close retention times and largely similar mass spectra with no specific ...features complicate unambiguous identification, especially of monosaccharides. An optimized pre-capillary ethoximation-silylation GC/MS method for determination of monosaccharides and disaccharides was applied to a wide range of analytes (46 compounds). The two-step derivatization resulted in a pair of syn and anti peaks with specific retention and intensity ratio. The resulting dataset of mass spectra was subjected to a PCA-based pattern recognition. An oxime peak identifier (OPI) of the carbohydrate analytes, based on the combination of an internal standard and the corresponding syn/anti peak ratios, increased the reliability of the identification of reducing carbohydrates. Finally, the introduced EtOx-TMS derivatization method was applied to four different carbohydrate matrices (agave sirup, maple sirup, palm sugar, and honey).
•Optimization of an EtOx/TMS derivatisation method for GC/MS analysis.•Evaluation of chromatographic and mass spectra characteristics of 46 carbohydrates.•Parameters were syn/anti peaks ratio, elution order and time shift between the peaks.•Dataset of mass spectra was subject to a PCA-based pattern recognition.•An oxime peak identifier (OPI) improves carbohydrate identification.
2,3-Dialdehyde cellulose (DAC) of a high degree of oxidation (92% relative to AGU units) prepared by oxidation of microcrystalline cellulose with sodium periodate (48 °C, 19 h) is soluble in hot ...water. Solution casting, slow air drying, hot pressing, and reinforcement by cellulose nanocrystals afforded films (∼100 μm thickness) that feature intriguing properties: they have very smooth surfaces (SEM), are highly flexible, and have good light transmittance for both the visible and near-infrared range (89-91%), high tensile strength (81-122 MPa), and modulus of elasticity (3.4-4.0 GPa) depending on hydration state and respective water content. The extraordinarily low oxygen permeation of <0.005 cm
μm m
day
kPa
(50% RH) and <0.03 cm
μm m
day
kPa
(80% RH) can be regarded as a particularly interesting feature of DAC films. The unusually high initial contact angle of about 67° revealed a rather low hydrophilicity compared to other oxidatively modified or unmodified cellulosic materials which is most likely the result of inter- and intramolecular hemiacetal and hemialdal formation during drying and pressing.
In combination with observations from visible satellite channels, near-infrared channels can provide valuable additional cloud information, e.g. on cloud phase and particle sizes, which is also ...complementary to the information content of thermal infrared channels. Exploiting near-infrared channels for operational data assimilation and model evaluation requires a sufficiently fast and accurate forward operator. This study presents an extension to the method for fast satellite image synthesis (MFASIS) that allows for simulating reflectances of the 1.6 µm near-infrared channel based on a computationally efficient neural network with the same accuracy that has already been achieved for visible channels. For this purpose, it is important to better represent vertical variations in effective cloud particle radii, as well as mixed-phase clouds and molecular absorption in the idealized profiles used to train the neural network. A new approach employing a two-layer model of water, ice and mixed-phase clouds is described, and the relative importance of the different input parameters characterizing the idealized profiles is analysed. A comprehensive data set sampled from Integrated Forecasting System (IFS) forecasts together with different parameterizations of the effective water and ice particle radii is used for the development and evaluation of the method. Further evaluation uses a month of ICOsahedral Non-hydrostatic development based on version 2.6.1 (ICON-D2) hindcasts with effective radii directly determined by the two-moment microphysics scheme of the model. In all cases, the mean absolute reflectance error achieved is about 0.01 or smaller, which is an order of magnitude smaller than typical differences between reflectance observations and corresponding model values. The errors related to the imperfect training of the neural networks present only a small contribution to the total error, and evaluating the networks takes less than a microsecond per column on standard CPUs. The method is also applicable for many other visible and near-infrared channels with weak water vapour sensitivity.
1-Alkyl-3-methylimidazolium ionic liquids are common cellulose solvents and biomass pretreatment agents, while beta-irradiation (“e-beaming”) is often used to decrease the recalcitrance of biomass ...towards hydrolysis or saccharification. Aiming at the general goal of elucidating the interaction between lignocellulosics, imidazolium-based ionic liquids, and beta-irradiation, we studied the effect of beta-irradiation on the pure ILs 1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium, both as chloride and acetate. Contrary to the expectation of inertness, irradiation caused degradation of the ILs, which was proportional to irradiation dosage,
i.e.
, to irradiation time and intensity. At a dosage of 2400 kGy, 0.2% (2000 ppm) of the IL were chemically altered. The main degradation pathway is the formation of imidazole and
N
-methylimidazole with concomitant dealkylation. The cleaved-off alkyl groups, apparently in cationic form, react with the anions present, accounting for the formation of alkyl chlorides and alkyl acetates from the chloride ILs and acetate ILs, respectively. A second, minor pathway comprises the degradation of the imidazole ring under conversion of the C
2
-unit from the former C4-C5 moiety into ethylenediamine and reaction of the C
1
-unit from the former C2 with the IL anions. Because of the non-neglible byproduct formation, the degradation of the ILs upon beta-irradiation and possible side reactions of the resulting byproducts need to be kept in mind for all setups that involve beta-irradiation and imidazolium ILs simultaneously.
Graphical abstract
A combination of swelling in imidazolium ionic liquids and beta-irradiation – both common pretreatments in biomass processing on their own – leads to unexpected effects, with beta-irradiation causing ...degradation of the pure ionic liquid and also modification of cellulose suspended in the ionic liquid. The underlying chemistry was investigated in a series of model compound experiments. Here, we report that beta-irradiation of the ionic liquid EMIM-OAc containing equimolar amounts of benzaldehyde and
d
-glucose affords an unexpected condensation product C
17
H
20
O
7
, of which the structure was elucidated as 5-(1
S
,2
R
,3
R
)-1,2,3,4-tetrahydroxybutyl-2-phenyl-3-furoic acid, applying a combination of analytical techniques, mainly NMR spectroscopy, after conversion into the ethyl ester derivative for purification. No reaction at all occurred without beta-irradiation under otherwise identical conditions. Intriguingly, the acetate – the IL´s anion – was incorporated into the condensation product, which can formally be regarded as the condensation product of benzoylacetic acid (from benzaldehyde and the IL´s acetate) and
d
-glucose. The reaction occurred only when all three components – acetate-type IL, glucose and PhCHO – were irradiated simultaneously. The structure elucidation of the compound is presented, along with a discussion of possible formation mechanisms. Future experiments need to address the generality of the reaction for conversion of other aldehydes and aldoses, and the question of whether a similar process occurs with the reducing end of celluloses or other polysaccharides.
Graphical Abstract
This paper discusses tolerance values and confidence levels for high-altitude electromagnetic pulse (HEMP) field tests. An HEMP simulator provides the HEMP environment with various degrees of ...completeness. Deviations from the ideal waveform occur due to the simulator structure and concept. In this paper, we review tolerance values for pulse parameter specified in civil and military standards. The impact of the tolerated deviations on the test objective will be discussed. In the second part, we stress the aspect of how an HEMP test must be performed to provide sufficient confidence in the HEMP survivability of the system under test. This part starts with a brief description of a usual HEMP test setup and test procedures. Characteristics of the test procedure as well as the typical behavior of systems under tests are analyzed with statistical methods. Based on the statistical analysis, we define a confidence level, a measure of the confidence in the test result.
The detection of individual chromophores that contribute to the overall discoloration of paper or pulp (“yellowing”) is a challenge because these substances are only present in extremely small ...amounts (ppm to ppb range). In this work, paper spray (PS) coupled with mass spectrometry was used to detect a low-concentrated cellulosic key-chromophore, 2,5-dihydroxyacetophenone (DHAP). Sensitivity was enhanced by derivatization with Girard's reagent T (GT). DHAP was successfully detected in historic paper samples and also was applied to model papers in order to investigate different factors that influence its generation: temperature, time, relative humidity, and the presence of iron ions, by means of a full factorial design. The main factors, temperature and relative humidity, have the most impact on the generation of DHAP, but the interactions between the factors are also significant and are therefore important for the degradation process. The historical papers containing DHAP were then compared to the artificially aged samples. The results were confirmed by independent, accurate mass measurements.
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•Online derivatization of a keychromophore.•Quantitative method for measurement of a specific cellulosic degradation product.•Monitoring artificial ageing process while varying parameters.•Fast and reliable method.
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. 60ng/g for each key chromophore, which allows for their successful detection in historic sample material.
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•Fast derivatization for enhanced detection of a key chromophore in historic documents.•Quantitative method with low sample demand.•No specialized equipment necessary.•New tool for understanding degradation processes in cellulosic substances.
Nitrification in forest soils is often associated with increased leaching of nitrate to deeper soil layers with potential impacts on groundwater resources, further enhanced under scenarios of ...anthropogenic atmospheric nitrogen deposition and predicted weather extremes. We aimed to disentangle the relationships between soil nitrification potential, seepage-mediated nitrate leaching and the vertical translocation of nitrifiers in soils of a temperate mixed beech forest in central Germany before, during and after the severe summer drought 2018. Leaching of nitrate assessed below the litter layer and in 4, 16 and 30 cm soil depth showed high temporal and vertical variation with maxima at 16 and 30 cm during and after the drought period. Maximum of soil potential nitrification activity of 4.4 mg N kg−1 d−1 only partially coincided with maximum nitrate leaching of 10.5 kg N ha−2. Both ammonia oxidizing bacteria (AOB), dominated by Nitrosospira sp., and ammonia oxidizing archaea (AOA), dominated by Nitrosotalea sp., were subject to translocation by seepage, and AOB decreased at least by half and AOA increased by one to three orders of magnitude in their abundance in seepage with increasing soil depth. Despite stable population densities in soil over time, abundances of AOA, AOB and total bacteria in seepage increased by one order of magnitude after the onset of autumn rewetting. Bacterial cells contributed an estimated 17–34% to the export of particulate organic carbon (POC) and particulate nitrogen (PN) below the litter layer with the highest contribution after drought and rewetting. Our findings suggest that not only microbial activity but also transport of microbial biomass itself may act as important driver of nutrient fluxes in forest soils. Predicted higher frequency of drought periods in temperate regions in the future may result in more frequent perturbations of nutrient fluxes and enhanced export of soil-derived microorganisms with implications for microbial community dynamics and metabolic potential in subsoils and subsurface environments.
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•AOB rather than AOA appeared to drive nitrification in calcareous forest soils.•Susceptibility to seepage-mediated translocation was taxon-specific.•Vertical translocation of AOA increased with increasing soil depth.
Fluorescence labeling with N-(1-naphthyl)ethylenediamine is highly effective for quantifying oxidized reducing end groups (REGs) in cellulosic materials. When combined with size exclusion ...chromatography in DMAc/LiCl, along with fluorescence / multiple-angle laser light scattering / refractive index detection, a detailed profile of C1-oxidized REGs relative to the molecular weight distribution of the cellulosic material can be obtained. In this work, the derivatization process was extensively optimized, to be carried out heterogeneously in the solvent N-methyl-2-pyrrolidone. Furthermore, we show that to achieve high selectivity for carboxyl groups at the C1 position, keto and aldehyde groups need to be selectively reduced (e.g., by NaBH4), and carboxyl groups other than at C1 need to be blocked (e.g., by methylation with (trimethylsilyl)diazomethane) prior to fluorescence labeling of carboxyl groups at C1 position. Finally, we demonstrate the practical value of the analytical method by measuring the content of the C1-oxidized REGs in cellulose samples after chemical (by Pinnick oxidation) or enzymatic (by treatment with C1-oxidizing LPMO enzymes) oxidation of various pulp samples.
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