一种用紫外光谱测定混合糖含量的新方法

提出一种用紫外光谱测定样品中混合糖含量的方法。其原理是基于样品中的糖经浓硫酸处理后生成有紫外吸收的糠醛和羟甲基糠醛,进行紫外波长吸收测定;通过化学计量学软件,根据一组已知糖浓度标准样品的多波长光谱和所对应组成浓度之间的数学关系,建立校正模型。将未知样品的紫外光谱信息输入校正模型即可预测其组成中糖的含量。本方法无需使用有机试剂,操作简便,可以测定样品中戊糖、己糖和总糖的含量,适合于木质生物质炼制研究中溶解性糖类组分的分析。     

Characterization of HETEs and related conjugated dienes by UV spectroscopy

Three distinct pairs of HETEs can be distinguished on the basis of their UV spectra. We used hydroxy-linoleates (hydroxy-octadeca-cis-trans-dienoates) as a base for comparisons; both the 9- and 13-hydroxy isomers have identical chromophores with λ_max near 234 nm. The presence of a double bond three carbons removed from the conjugated diene (the chromophore of 9- and 11-HETE) causes a shift in the observed λ_max to near 235 nm. A double bond β to the chromophore (5- and 15-HETE) gives a further shift of 1.5 nm, giving a λ_max between 236–236.5 nm. With double bonds in both these positions (8- and 12-HETE), the λ_max is observed near 237 nm. It is apparent that the exact λ_max of thecis-trans diene chromophore is influenced in a consistent way by the adjacent methylene interruptedcis double bonds. hydroxylinoleate, describes the two primary products of linoleate oxygenation, more properly named 9-hydroxy-octadeca-10trans,12cis-dienoate and 13-hydroxy-octadeca-9cis,11trans-dienoate. Hydroxylinoelaidate refers to the correspondingall-trans dienes. RH-HPLC, reversed-phase high pressure liquid chromatography; SP-HPLC, straight-phase high pressure liquid chromatography.     

Reaction of cellulose xanthate with chromium compounds by UV spectroscopy

Conclusions The type of chemical bond in the chromium compounds obtained which are based on cellulose xanthate has been ascertained.It has been shown that, as a result of an oxidation-reduction reaction between the thiocarbonate groups of the cellulose xanthate and K₂Cr₂O₇ (in acid medium), a chromium xanthate is formed which has a covalent type of bond between the sulfur atoms and chromium.Translated from Khimicheskie Volokna, No. 6, pp. 29–30, November–December, 1987.     

苯乙烯-异戊二烯-丁二烯三元集成胶乳增韧ABS树脂

采用自由基乳液聚合方法,通过苯乙烯-异戊二烯-丁二烯三元共聚合技术,设计合成了新型三元集成胶乳（SIBL）替代传统成本较高的聚丁二烯胶乳（PBL）,制备丙烯腈-丁二烯-苯乙烯共聚物（ABS树脂）。将高温乳液法制备的SIBL进行附聚,再经过乳液接枝法制备高胶含量的ABS粉料,最后将ABS粉料与本体苯乙烯-丙烯腈共聚物（SAN树脂）掺混、熔融挤出、造粒,制备了低成本新型ABS树脂。考察三种单体配比对SIBL聚合动力学和粒径大小、分布、凝胶含量及玻璃化转变温度（T_g）的影响规律;研究单体配比对SIBL接枝反应和ABS树脂性能影响规律。结果表明: 采用自由基乳液聚合制备三元集成胶乳的方法可行,得到的增韧ABS树脂综合性能优异,其中最具代表ABS树脂韧性的悬臂梁缺口冲击强度得到显著提高,由139J/m提高到233J/m。     

Polymer analysis by higher-order UV/VIS-derivative spectrophotometry

Summary High resolution higher-order UV/VIS derivative spectrophotometry (HODS) has been used for some selected analytical problems of polymers, such as copolymer composition, determination of unconverted monomer in polymer and analysis of polymer additives.Dedicated to Professor Kurt Dialer on his 60th birthday     

紫外光谱定量测定木质纤维预水解液中溶解性木素和糠醛含量

采用紫外光谱探讨了低分子有机酸、糠醛和木质纤维高温预水解液(PHL)的紫外吸收谱图特征。甲酸和乙酸在近205 nm处有显著吸收, 而糠醛在近280 nm处有显著吸收, 以205 nm或280 nm为木素特征吸收位置的传统木素测定方法不适于高温预水解液的溶解性木素测定。研究提出碱性硼氢化钠还原处理预水解液, 消除糠醛的紫外吸收, 进而定量测定溶解性木素含量的方法。结果表明, 硼氢化钠可显著降低近280 nm处吸收值, 预水解条件越高, 还原前后吸收差值降低越多, 说明糠醛类物质含量高。以提取相思木和芦苇木素为标样, 280 nm处吸光度与浓度线性相关系数均达到0.999, 满足定量测定的需要。充分还原前后280 nm吸收差值可用于糠醛的定量, 糠醛标样280 nm处吸光度与浓度线性相关性为0.998, 糠醛测定回收率为98.14%~99.88%, 相对标准偏差为0.17%~0.35%。     

The electronic structure of oxide-supported tungsten oxide catalysts as studied by UV spectroscopy

The UV spectra of tungsten oxide catalysts supported on alumina, titania and zirconia, and on titania–alumina and titania–zirconia mixed oxides are reported and discussed. Evidence is provided for the different electronic structure of supports and catalysts, which could affect the behavior of the tungsten oxide centres in the different cases. On alumina, tungsten oxide centres are “isolated” by the insulating support, while on titania-based materials they are likely in electronic contact with each other and with Ti centres through the support conduction band. In the case of WOx2013;ZrO₂, the 5d levels of tungsten ions fall just below of the lower energy limit of the support conduction band. This revised version was published online in July 2006 with corrections to the Cover Date.     

紫外光谱测定葡萄糖两相水解液中5-羟甲基糠醛的新方法

采用紫外光谱法快速测定了葡萄糖两相水解液中的5-羟甲基糠醛(5-HMF)的摩尔浓度,实验表明:以5-HMF为标准品,蒸馏水替代葡萄糖的水-二甲基亚砜两相溶液为空白,在284 nm波长处对其中的5-HMF进行了定量分析。测定结果表明,溶液中的5-HMF摩尔浓度在0～0.10 mmol/L范围内与其吸光度值呈现良好的线性关系,并且重现性良好。该方法在抗干扰性实验、精密度实验、回收率实验、稳定性实验和检出限方面均有满意表现,适于快速、准确地测定5-HMF摩尔浓度。     

Film formation analysis by diffusive wave spectroscopy

The thin layer analysis is very important for several sectors of industry. Indeed, environmental laws and improvement of performances lead the manufacturers to innovate in the field of coatings and paints. Several classical techniques of characterization (TGA, DMA, etc.) used with this intention do not allow to perform the analysis in situ and are often long and tedious to set up. We propose to solve this problem with a new optical process. Its technology based on multi-speckle diffusive wave spectroscopy (MS-DWS) allows making real-time analysis in a non-destructive way thanks to an optical measurement. The aim of this work is to highlight correlations between this new technology and the classical methods of analysis. Two film forming polymeric materials were studied, a polydimethylsiloxane (PDMS) and a commercial paint based on an aqueous dispersion of acrylic copolymers. The PDMS was chosen for the simplicity of its film forming process and is used as model. The paint having a more complex drying mechanism enables to complete this study.     

Copolymer characterization by surface tension

The use of surface tension measurements is proposed as a simple method for the determination of copolymerization ratios. The procedure depends on the parachor of the copolymer in the liquid state (∏), which is defined by ∏ = ∏_s + ∏₀(w_p/w_s)(M_s/M₀) for solutions and ∏ = [DP]∏₀ for liquid or molten polymers, where ∏_s is the parachor of the solvent of molecular weight M_s; w_p and w_s are the weights of the polymer and solvent in solution; while ∏₀ and M₀ are the parachor and molecular weight of the repeating unit of the copolymer, respectively. The validity of this relationship is demonstrated by analysis of the surface tension properties of liquid silicone polymers, polystyrene–Decalin solutions, and molten polymers as well as by the calculation of the composition of some characterized tetrahydrofuran–propylene oxide copolymers. The application of surface tension measurement is also suggested as a means of estimating the degree of chain branching in a polymer.     

Low-density polyethylene depth profile analysis by photoacoustic spectroscopy

Near-infrared photoacoustic spectra of polyethylene (1 mm slab) were taken in the modulation range 10–240 Hz, which corresponds to thermal diffusion layers in the 56?11 μm range. Thick-layer spectra are very similar to polyethylene film transmission spectra, but large differences are observed between the spectra taken at various modulation frequencies. From 10 to 80 Hz, all the spectral band intensities decrease linearly with ω^?a where ω is the light modulation frequency and a varies from 0.48 to 1.00 for different constituent groups. The analysis of spectral intensity as a function of modulation frequency shows that peak intensity ratios of ? CH₃, ?CH₂, and ? OH groups, relative to that of methylene groups, increase as thinner, closer-to-surface polymer layers are sampled. From this we conclude that near-to-surface layers of solid polyethylene are richer in ? CH₃, ?CH₂ and ? OH groups than the polymer bulk.     

我国苯乙烯嵌段共聚物的发展前景分析

苯乙烯类嵌段共聚物（简称SBC）是由苯乙烯与丁二烯（和／或者异戊二烯）以烷基锂为催化剂进行阴离子溶液聚合制得的一种热塑性弹性体．主要包括苯乙烯一丁二烯一苯乙烯嵌段共聚物（简称SBS）、苯乙烯一异戊二烯一苯乙烯嵌段共聚物（简称SIS）以及它们相应的加氢产物——氢化SBS（简称SEBS）和氢化SIS（简称SEPS）4种类型,在制鞋业、塑料改性、沥青改性、防水涂料、液封材料、电线、电缆、汽车部件、医疗器械部件、家用电器、办公自动化和胶粘剂等方面具有广泛的应用     

Monitoring the UV degradation of PVC window frames by microhardness analysis

While well-known methods of bulk analysis of thermal degradation of PVC become standard industrial tools, techniques for the study of surface damage produced by weathering are not generally considered. In this paper we present a new test, based on microhardness measurements, which can be used as a complementary technique for the study of this phenomenon. Comparison of this method with color changes and specific elongation at break measurement has been established for PVC window frames.     

UV/HREELS spectroscopy of benzene on Pt(110)

Some years ago, LEED studies of Ogletree et al. and Wander et al. found that benzene undergoes a structural rearrangement when the benzene adsorbs on platinum. In contrast, Horsley et al. proposed that the benzene adsorbs without undergoing significant distortion. In this paper UV/HREELS spectroscopy is used to examine benzene adsorption on Pt(110). We find that the benzene can adsorb into two different states: a weakly bound form of benzene with UV/HREELS spectrum similar to gas-phase benzene, and a strongly bound form of benzene with UV/HREELS and IR/HREELS spectra which are consistent with formation of a diene (e.g., 1,4-cyclohexadiene). A comparison of our data to the results of Wander et al. and Horsley et al. shows that the weakly bound form of benzene is consistent with Horsley’s assignments, while the strongly bound species looks as expected from the work of Wander et al. The conclusion from our study then is that Wander et al. and Horsley et al. are both correct. They are just studying different forms of benzene on the platinum surface. This revised version was published online in July 2006 with corrections to the Cover Date.     

新型丙烯-乙烯共聚物增韧聚丙烯的研究

丙烯-乙烯共聚物Vistamaxx（VM）是一种丙烯摩尔含量占70％以上的新型弹性体。用VM增韧聚丙烯（PP），考察了PP／VM共混物的力学性能、微观形态结构以及结晶性能，并与乙烯-辛烯共聚物（POE）与PP的共混体系进行了对比。结果表明，常温下VM增韧效果优于POE，PP／VM体系拉伸性能优于PP／POE体系；VM在PP中表现出比POE更好的分散性；VM具有与PP相同的晶型，VM的加入细化了PP的晶粒。     

紫外光谱技术在超临界流体技术中的应用

在阐述超临界CO2萃取工艺原理的基础上,分别介绍了离线和在线紫外-可见光光谱技术在超临界流体技术中的应用情况,分析了在线紫外光谱技术的应用特点,指出了在线检测应用中所遇到的问题,同时对其前景进行了展望。     

Structural analysis of polycrystalline graphene systems by Raman spectroscopy

A theoretical model supported by experimental results explains the dependence of the Raman scattering signal on the evolution of structural parameters along the amorphization trajectory of polycrystalline graphene systems. Four parameters rule the scattering efficiencies, two structural and two related to the scattering dynamics. With the crystallite sizes previously defined from X-ray diffraction and microscopy experiments, the three other parameters (the average grain boundaries width, the phonon coherence length, and the electron coherence length) are extracted from the Raman data with the geometrical model proposed here. The broadly used intensity ratio between the C–C stretching (G band) and the defect-induced (D band) modes should be used to measure samples with crystallite sizes larger than the phonon coherence length, which is found equal to 32 nm. The Raman linewidth of the G band is more appropriate to characterize the crystallite sizes below the phonon coherence length, down to the average grain boundaries width, which is found to be 2.8 nm. “Ready-to-use” equations to determine the crystallite dimensions based on the Raman spectroscopy data are given.