Determination of carbohydrate- and lignin-derived components in complex effluents from cellulose processing by capillary electrophoresis with electrospray ionization-mass spectrometric detection

Degradation products from lignocellulosic materials receive increasing attention due to the continuously growing interest in their utilization. The inherent structural variance of lignocellulosics combined with the intricacy of lignocellulosic processing (e.g. pulping of wood and bleaching of cellulosic pulps) and the complexity of degradation processes occurring therein result in rather complex mixtures in the process streams and effluents that contain a large quantity of structurally different degradation products. This is true for most processing steps, but also for degradation reactions occurring during aging of lignocellulosic materials, such as paper, cellulosic tissue or textiles. In order to render such mixtures better analytically accessible than hitherto possible a CE-ESI-MS method was established for the simultaneous determination of aliphatic carboxylic acids from the degradation of (hemi)celluloses and aromatic compounds from lignin degradation. CE and ESI-MS parameters have been optimized towards sensitivity and good reproducibility. The method was tested in two real-world scenarios: the determination of major components in effluents from bleaching stages in the pulp and paper industry, and the analysis of degradation products in extracts of naturally aged papers. The advantages and drawbacks of this approach are critically discussed.     

XPS analysis of NH3 plasma-treated polystyrene films utilizing gas phase chemical modification

Gas phase chemical modification (GCM) is found to be more preferable as a pretreatment for the XPS surface analysis of polymer materials than the conventional liquid phase treatment because it can circumvent problems such as solvent contamination and swelling. We have tried the quantification of the surface composition successfully by estimating the yield of the reaction from model samples. GCM was then applied to correlate the surface composition of NH₃ plasma-treated polystyrene films with their cell-affinity. The amount of primary-amine and that of carboxylic acid were directly determined by GCM. Although the amount of primary-amine, 15–20% of total nitrogen, did not depend on the treatment intensity, the total amine content for the treated samples increased with the plasma treatment intensity. The quantity of carboxylic acid generated was found to be very small. All treated samples had better cell-affinity than the control. The sample N2 (of medium treatment) showed the best cell-affinity. The most strongly treated sample N3, with larger amine content than N2, showed worse cell-affinity because of the interference by the sputtered SiO₂ on the surface.     

Gd-Ba-Cu-O超导膜的XPS研究

用XPS对不同凡的Gd-Ba-Cu-O超导膜做了定量、角分布、成象和离子剥蚀纵深分析．结果表明：样品表面都存在Ba富集和Gd短缺,表面原子微观分布不均匀;表面和纵深都存在含C物质污染;与Tc≥87K的样品比较,Tc≤77K的膜表面对应于非超导相的Ba和O原子浓度最高,膜的纵深处的原子组成仍偏离化学计量,而且膜表面和纵深处的含C物污染最严重．     

Characterization of sediment reference materials by x-ray photoelectron spectroscopy

The chemical composition of surface layers of three sediment reference materials, Pond Sediment (Japan NIES CRM No. 2), River Sediment (US NBS SRM 1645) and Estuarine Sediment (US NBS SRM 1646), has been studied comparatively by X-ray photoelectron spectroscopy (XPS). The composition of River Sediment as determined by XPS is peculiar in that the concentration of Cr is much higher but that of Si is much lower than that expected from the bulk composition of the sample. This can be attributed to the structure of the sediment particles, which consist of silica-rich cores covered by surface layers rich in Cr(III). Organic substances are predominant in the surface layers of all three materials, as indicated by the C 1s and N 1s lines. The elemental composition of the surface layers can be reasonably related to the origin of the sediments. The bonding states of some elements in the sediment samples, deduced from the photoelectron binding energies, are briefly discussed.     

XPS和TOF—SIMS在硬盘驱动器（HDD）磁头表面微污染分析中的应用

XPS和TOF－SIMS表面分析仪器联用分析磁头臂焊接位表面有机微污染物成分,找出污染物的来源;XPS能够提供污染物中元素组成及价态信息,而TOF－SIMS能够提供其分子信息。试验证明两者联用是分析表面有机微污染物强有力的手段。     

XPS characterization of wood chemical composition after heat‐treatment

XPS was used to characterize the chemical changes occurring after drying or applying a heat‐treatment to beech wood samples. Our results indicate that the surface of this air‐exposed material could be strongly affected either by the ambient atmosphere during storage or by the complex atmosphere in the oven during drying or heat‐treatment. However, the O/C ratio measured after removal of a thin slice of a few millimetres of an untreated sample is in reasonable agreement with that calculated from the well‐established chemical composition of beech. Through this methodology (equivalent to scraping for hard materials) it is expected to get a realistic characterization of the wood. The reliability and repeatability of the XPS measurements have been checked and the method applied to the study of the chemical changes of the beech samples subjected to heat‐treatment. Heating at 240 °C induces a significant decrease of the O/C ratio from 0.55 before to 0.44 after the treatment. Heat‐treatment induces also a decrease of the C₂ carbon contribution (carbon atom bound to a single non‐carbonyl oxygen) associated with an increase of the C₁ carbon contribution (carbon atoms bound only to carbon or hydrogen atoms), in agreement with chemical modifications reported previously in the literature. Thanks to the small analysed area of the equipment used in this study, different spots were analysed to demonstrate the presence or absence of a gradient of chemical composition due to thermal degradation or migration of extractives from within the wood structure to its surface. At the scale of our observations, the different wood samples investigated (dried or heat treated) appear to be homogeneous. Copyright © 2006 John Wiley & Sons, Ltd.     

钙钛矿型氧化物A(Mg、Ca、Sr)TiO_3的结构及其光催化性能研究

钙钛矿型ABO_3复合氧化物具有良好的热稳定性、催化性能、磁性、导电性以及传感等性质~([1-5]).目前钙钛矿结构复合氧化物以其优异的性能已成为光催化领域的研究热点之一~([6-9]).在钙钛矿型ABO_3复合氧化物中,A位金属可以起到稳定结构的作用,而B位金属为活性位.但是,当B位金属相同A位金属不同的一类钙钛矿型氧化物作为催化剂时,影响其光催化活性的主要因素很少见文献报道.     

超声溶胶-凝胶法制备强酸性介孔材料

 在不使用有机模板剂和孔调节剂的情况下,以无机盐为原料制备了锆和钛修饰的硅铝介孔材料及担载铂的电子-酸性双功能介孔材料. 激光粒度仪和N2吸附-脱附等温线表征的结果显示,制备方法对溶胶的粒度分布和材料的结构性质有较大的影响. 吡啶吸附-脱附的红外光谱表明所得材料具有强的表面酸性,利用XPS和H2-TPR等表征手段确定了材料强表面酸性的来源. 1-己烯加氢异构反应表明所合成的材料具有良好的催化活性.     

A guide for the meaningful surface analysis of wood by XPS and ToF-SIMS

The surface analysis of wood and wood products is becoming increasingly important for reasons ranging from the investigation of molecular constituents through to the optimization of industrial processes. As with any natural product, wood analysis is not straightforward, and this review aims to provide guidance for the successful surface analysis of wood by XPS and ToF-SIMS. Through example experiments, three themes are addressed relevant to obtaining meaningful results: considerations related to heterogeneity in the composition of wood (e.g., growth rings); the impact of the chemical removal of minor wood components known as extractives, and whether such a process is necessary; and the potential for misleading or erroneous results as a result of contamination occurring during sample preparation. In addition to discussing successful sample preparation approaches, the important role to be played by MVA in surface analysis is emphasized, particularly in the analysis of ToF-SIMS data. Examples of ToF-SIMS/MVA are provided that highlight the identification of contamination in sample preparation, the quantification of wood composition in terms of cellulose and lignin, and the indication of age of softwood samples. Through consideration of the complexities that influence wood surface analysis, the design and interpretation of consequential experiments become easier and more accurate.     

X射线光电子能谱仪的数据采集及预处理技巧研究

X射线光电子能谱(XPS)广泛应用于材料表面分析表征,因XPS分析方法的主观性相对较强,谱图测试及分析水平会对数据分析质量产生很大影响。为获得更好的数据质量,文章根据国际标准和实际测试经验总结出一种通用于不同类型材料表面分析表征的XPS数据采集和预处理分析思路,以方便测试人员能够更加系统的进行数据采集和分析,为材料研发人员提供更加全面的元素组成信息和谱图解析注意事项,从而更有效地助力材料表面分析研究,该方法对科研工作者分析准确度的提高具有重要的理论意义和实际应用价值。     

Pyrolysis of various biomass residues and char utilization for the production of activated carbons

Biomass samples (almond shell, walnut shell, almond tree pruning and olive stone) were subjected to thermoanalytical investigation to evaluate their thermal behaviour and its correlation with their lignocellulosic composition. Then, the pyrolysis process of these materials was studied in terms of the energy content of the phases generated (gas and liquid). Finally, the feasibility of obtaining effective adsorbents from the char generated was studied. With this aim, the char was used to prepare activated carbons (ACs) by steam gasification at fixed activation temperature and time, identical for the four chars. The differences found in the porosity development of the activated carbons were related to the lignocellulosic composition of the raw material. It is shown that the four biomass residues used are versatile precursors that allow the preparation of adsorbent materials with different textural characteristics.     

镧系离子掺杂TiO2的制备及其对咪唑降解反应的光催化活性

 以TiCl4和镧系元素的氯化盐溶液为前驱体,采用溶胶-凝胶法制备了不同含量镧系离子掺杂的TiO2光催化剂,用X射线衍射(XRD)、 光致发光光谱(PLS)、 表面光电压谱(SPS)和X射线光电子能谱(XPS)对催化剂进行了表征. XRD结果表明,样品为锐钛矿和金红石的混晶相,镧系离子未进入到TiO2晶格中. PLS和SPS测定结果表明,随着掺杂离子的不同和掺杂含量的不同,样品的谱强度呈现有规律的变化. 在紫外光照射下,以咪唑为目标降解物比较了催化剂的光催化活性. 结果表明,适当含量的镧系离子掺杂可有效促进TiO2表面光生载流子的分离,从而显著提高其光催化活性.     

Characterization of waterlogged wood by NMR and GPC techniques

Anaerobic erosion bacteria can slowly degrade waterlogged wood, causing a loss of cellulose and hemicellulose. During this process, lignin can also be altered. For this reason, the chemical characterization of waterlogged archaeological wood is crucial for both the elucidation of the degradation processes and also the development of consolidation and conservation procedures.The complex structure of wood makes it practically impossible to dissolve wood in its native form in conventional molecular solvents. Ionic liquids can provide a homogeneous reaction medium for wood-based lignocellulosic materials. Highly substituted lignocellulosic esters and phosphite esters can be obtained under mild conditions by reacting pulverized wood dissolved in ionic liquid with either acyl chlorides or dioxaphospholanes in the presence of pyridine. As a result, the functionalized wood develops an enhanced solubility in molecular solvents, allowing for a complete characterization by means of spectroscopic and chromatographic techniques.In this study, archaeological woods and reference sound woods of the same taxa (Quercus and Arbutus unedo), along with the corresponding extracted lignin, were fully characterized by means of phosphorus NMR spectroscopy, two dimensional NMR spectroscopy and GPC analysis. The samples were collected from the Site of the Ancient Ships of San Rossore (Pisa, Italy), where many shipwrecks dating from 2nd century BC to 5th century AD have been discovered.The results highlighted a deeper and faster depolymerization of the polysaccharide matrix against a limited degradation of the lignin fraction. The use of innovative solvent system as the ionic liquid [amim]Cl enables to highlight chemical and morphologic changes in wood composition avoiding further degradation.     

Microanalysis of polymers using a windowless energy-dispersive X-ray detector

The surface compositions of various polymeric films, grown electrochemically on platinum foils, have been investigated by energy-dispersive x-ray analysis in conjunction with scanning electron microscopy (SEM/EDS). Comparison of the relative area ratios of peaks for the C and N K_emission lines show that the EDS may be used to study the surface composition of polymers. The evidence presented strongly suggests that there is limited structural degradation and the elemental composition is not changed under the electron beam at relatively low accelerating voltages. This technique statistically samples the repeat units of the polymer. For samples grown in both aqueous and nonaqueous solutions. SEM/EDS provides evidence for extensive contamination with oxygen.     

Radiation‐induced migration of additives in PVC‐based biomedical disposable devices Part 2. Surface analysis by XPS

Extruded parts of non‐sterilized and β‐irradiated (25 and 50 kGy) plasticized poly(vinyl chloride) (PVC) used for disposable medical devices have been studied to investigate the effect of sterilization on surface chemical composition. The polymer surfaces were analysed using angle‐resolved x‐ray photoelectron spectroscopy. The inner surface of the blood tubing lines showed a fairly smooth surface both before and after sterilization, so a laterally homogeneous surface can be assumed for XPS analysis. The XPS survey spectra exhibited no signals besides carbon, chlorine, oxygen and calcium. Detailed analysis of the regions showed the C 1s, Cl 2p and O 1s signals to be multi‐component, presenting signals of the PVC, the plasticizer and the other additives. Binding energies remained constant irrespective of β‐radiation dosage, but the amount of chlorine component at 198.4 ± 0.1 eV (associated with modified PVC) decreased with sterilization dosage. Angle‐resolved XPS revealed that this component is located at the outermost surface of the polymer. It can be hypothesized that the production processes themselves (extrusion and/or injection molded) already induce modifications of the polymer surface and also lead to surface segregation of the plasticizer. During the subsequent thermal sterilization of the polymer dehydrochlorination continues but, because of the very short time required by the β‐irradiation technology to sterilize devices, the atmospheric oxygen is unable to diffuse into the irradiated material, thus inhibiting further side‐degradation of the materials, such as thermo‐oxidative degradation. Copyright © 2003 John Wiley & Sons, Ltd.     

Benchtop methods for measuring the fraction of free liquid of biomass slurries

The free-liquid fraction of slurries is strongly correlated with other slurry properties, especially the rheological and transport properties. Measuring free-liquid fraction can be problematic with lignocellulosic materials, and many studies to-date have instead used the total mass-fraction of liquid as a surrogate measure. This study presents two bench-scale methods for determining the free-liquid content of lignocellulosic biomass slurries. One is based on centrifuge-filtration of biomass for increasing time intervals until an asymptote is observed. The other uses solute exclusion methods and includes a proper accounting for unavoidable adsorption of the tracer solute molecules on the biomass solids. Overall, we found both methods gave reasonable results for washed pretreated corn stover. Among our controls, the centrifuge dewatering method tends to enable better results for large, rigid particles, and can give unrealistic results for small, compressible particles. This tendency is also reflected in the results for different pretreated corn stover slurries, where the quality of the results varied with the particle size distribution of the slurries. The solute exclusion method gives physically realistic results for all of our control materials and for washed pretreated materials, but produced physically unrealistic results for one unwashed pretreated corn stover sample. Further, we show that blue dextran interacts chemically with lignocellulosic material via adsorption and suspected degradation reactions.     

Determination of Surface Functional Groups in Lignocellulosic Materials by Chemical Derivatization and ESCA Analysis

Simple and convenient methods for determining surface chemical composition of lignocellulosic materials are described. The methods are based on vapor phase fluorine surface derivatization with either trifluoro acetic anhydride (TFAA), tri-fluoro ethanol (TFE) or pentafluorophenyl hydrazine (PFPH) and subsequent Electron Spectroscopy for Chemical Analysis (ESCA). Model cellulosic surfaces with well defined functionalities were used to optimize the derivatization reaction conditions. Detection and accessibility of surface hydroxyl functional groups were investigated in cotton and regenerated cellulose as models. Carboxymethyl cellulose (CMC) was used as a model surface for detection and quantification of carboxylic acid groups. Theoretical conversion curves for derivatization reactions were calculated and used to evaluate the extent of the reactions on the model surfaces. It was found that the conversion was higher for the regenerated cellulose and CMC than for cotton. The protocols developed using the model surfaces were applied to a case study on wood fibers with different degrees of complexity, namely dissolving and chemithermomechanical (CTMP) pulp. Untreated and oxygen-plasma modified pulps were compared with respect to the surface composition of functional groups. According to the derivatization reactions, functionalities containing oxygen were significantly increased on the plasma-treated samples. The effect of the treatment was found to be dependent on the type of pulp. Fluorine derivatization is shown to be an unambiguous method for clear assessment of the chemical functionalities of cellulosic surfaces.     

Quantitative analysis of trace levels of surface contamination by X‐ray photoelectron spectroscopy. Part II: Systematic uncertainties and absolute quantification

We discuss analyses of trace levels of surface contamination using X‐ray photoelectron spectroscopy (XPS). The problem of quantifying common sources of statistical and systematic uncertainties for these measurements is formulated in terms of the needs of extreme ultraviolet lithography, but the results and conclusions are applicable to a broad range of XPS applications. We quantify the systematic uncertainties introduced by particular cases of overlapping peaks on different substrate structures by simulating measured spectra with the National Institute of Standards and Technology Database for the Simulation of Electron Spectra for Surface Analysis (SESSA). One example demonstrates that the relative atomic concentrations of trace elements such as S, P, and halogens on a Ru surface could be dramatically overestimated if the fitting of the overlapping Ru 3d and C 1s peaks excludes the contribution from carbon. We also show how spectra generated by SESSA can be compared with measured spectra to determine absolute amounts of surface impurities on layered samples of the type used for extreme ultraviolet lithography. We provide estimates of the total uncertainty for such measurements by considering the systematic limitations of SESSA and the statistical uncertainties of the measurements. The same procedure can be employed for other multilayered materials. Finally, we describe two approaches for converting XPS detection limits for an elemental impurity in an elemental matrix to the corresponding detection limits for the impurity as a thin film on the surface of the matrix material.     

XPS investigation on the surface chemistry of corrosion products on ZnMgAl-coated steel

In this work, a novel evaluation strategy for the X-ray photoelectron spectroscopy (XPS) chemical assessment is proposed to identify the corrosion products formed on the surface of hot-dip galvanized ZnMgAl coatings after exposure to standardized salt spray tests. The experiments demonstrate that the investigated system exhibits a problematic differential charging behavior between the different compounds, an effect which cannot be fully compensated for by the flood gun of the XPS system, making a reliable evaluation of the individual spectra impossible by using standard evaluation and fitting methods. For that reason, a new effective approach—taking the different charge shifts into account—was implemented and its reliability experimentally verified on model mixtures of assumed corrosion products with known composition. With this new approach, the chemical surface composition of an industrial sample of a corroded ZnMgAl coating was revealed and discussed in order to clearly demonstrate the potential of the proposed method for future corrosion studies.     

Extracting information on the surface monomer unit distribution of PLGA by ToF‐SIMS

The surface chemistry of a range of random poly l‐lactide‐co‐glycolide (PLGA) materials has been investigated using XPS, static secondary ion mass spectrometry (SSIMS) and gentle secondary ion mass spectrometry (G‐SIMS). The estimated mole fraction of lactide units provided by SSIMS was in good agreement with bulk composition and appeared not to have been affected by contamination. Conversely, XPS assessment of lactide compositions was unreliable due to hydrocarbon contamination contributions. In this study, we propose a novel model to demonstrate that by using SSIMS it is possible to infer the degree of trans‐esterification for PLGA co‐polymers synthesised from a mixture of lactide and glycolide homo‐dimers. This was determined by introducing two independent parameters, the ratio of trans‐esterified bonds to the total number of ester bonds, P_T, and the lactide composition. The model has indicated that, for this set of polymers, P_T was approximately 0.25. Furthermore, we have demonstrated that G‐SIMS successfully identified the structurally important key fragments leading to direct identification. Analysis by G‐SIMS showed that the glycolic acid units from all PLGA compositions are emitted in a lower energy‐fragmentation process than lactic acid units. Copyright © 2008 John Wiley & Sons, Ltd.