Pulse Fourier Transform 13C-NMR Spectroscopy,Principles and Applications

As a result of the development of pulse Fourier transform NMR spectroscopy ¹³C resonance has become accepted as a means of elucidating the structures of organic compounds having the natural ¹³C abundance. Assignment of the signals is facilitated by broad-band and off resonance proton decoupling and by knowledge of longitudinal relaxation times. The pulse Fourier technique, which is more sensitive and faster than conventional NMR spectroscopy because of multi-channel excitation, allows ¹³C measurements within a short time even on dilute samples of high molecular weight compounds without prior enrichment in ¹³C.     

傅里叶变换红外光谱和傅里叶变换拉曼光谱法无损鉴别药材的真伪

利用傅里叶变换红外（FT-IR）和近红外傅里叶变换拉曼（NIR FT-aman）光谱法对大黄（西宁大黄）与伪品大黄（华北大黄、山大黄、水根大黄）进行了无损快速的鉴别。结果表明：尽管正品大黄与伪品大黄差别较小，有大部分的化学成分有很大的相同之处，但在红外、拉曼谱图中各自的特征峰较突出，根据谱峰的强度和位置可容易地将它们区别开来。红外和拉曼光谱法相互印证，相互补充，具有快速、准确、操作简单、重复性好、不需对样品进行分离提取，可直接鉴别等特点。     

Thermogravimetric Fourier Transform Infrared Spectroscopy of Hydrocarbon Fuel Residues

Although thermogravimetric analysis (TG) has become an indispensable tool for the analysis and characterization of materials, its scope is limited as no information is obtained about the qualitative aspects of the evolved gases during the thermal decomposition. For processes involving mass loss, a powerful technique to provide this missing information is Fourier transform infrared spectroscopy (FT-IR) in combination with TG. It supplies a comprehensive understanding of thermal events in a reliable and meaningful way as data are obtained from a single sample under the same conditions. The coupling TG/FT-IR is used in fuel analysis for the identification of residual volatiles, to determine their sequence of release and to resolve thermogravimetric curves. In this work, the usefulness of TG/FT-IR for characterizing middle distillate fuel residues is illustrated with some typical examples of recent application. A Bio-Rad FTS 25 FT-IR spectrometer coupled with a TA Instruments TGA 2950 thermogravimetric analyzer was used for data aquisition. The results obtained demonstrate the utility of this combined technique in determining the decomposition pathway of tarry materials at various stages of pyrolysis, thereby allowing new insights into the complex thermal behaviour of hydrocarbon residual systems. This revised version was published online in August 2006 with corrections to the Cover Date.     

嵌段共聚物傅里叶变换拉曼光谱

用傅里叶变换拉曼光谱(FT-Paman)研究了聚环氧乙烷-聚环氧丙烷-聚环氧乙烷(PEO-PPO-PEO)嵌段共聚物的无水样品,发现某些谱带对PEO0-PPO-PEO嵌段共聚物的结构和构象变化敏感,其中某些峰的相对强度的PPO/PEO比率和共聚物的构象有关,研究表明PluronicF68和F88具有一些反式构象的螺旋结构,PluronicP103(P123)是无规则结构,其它的嵌段共聚物处于二者之间.     

Fourier Transform Nuclear Magnetic Resonance Spectroscopy of Commercial Polysiloxanes

Abstract

Multinuclear Fourier transform nmr spectroscopy is shown to be a potentially useful technique for the evaluation of commercial polysiloxanes. H, ²⁹Si: and ¹³C nmr spectra are reported of the precursor solutions for RTV silicones. The ¹³C show the increased presence of an unidentified material in unacceptable lots of one of the two precursor solutions.     

鞋底材料的傅立叶变换红外光谱类型分析

利用傅立叶变换红外光谱技术对收集的29种皮鞋类黑色鞋底样品进行了测定分析,其中24种样品来自不同品牌或型号,5种样品来自同一品牌同一厂家同一批次.从红外光谱图中可以看出,依据红外光谱图中特征峰的峰数、峰位、峰形可将29个鞋底样品分为3大类.同一大类的部分鞋底样品有着相似的红外光谱特征,但在相对峰高比和指纹区中一些弱吸收峰上仍然存在明显差异.同一品牌同一厂家同一批次的鞋底样品红外光谱特征基本一致.这表明傅立叶变换红外光谱法是鉴别鞋底材料的有效方法,可以为案件现场遗留的各种鞋底材料残渣及其擦痕提供种属鉴别及比对分析.     

傅立叶变换离子回旋共振质谱及其研究进展

本文综述了傅立叶变换离子回旋共振质谱的基本原理及其颇具特色的数据处理方法.以两种典型的离子化方法为代表,介绍了目前主要使用的离子源,并总结了该方法在分析科学,尤其是在大分子分析、气相离子反应动力学研究和复杂体系分析等领域中的广泛应用.     

傅利叶变换光谱技术中的"折叠假线"研究

根据奈奎斯特(Nyquist)采样定理,解释了傅利叶变换光谱采集过程中由于折叠而出现的假线现象,并且对假线的特点进行了预测,进而总结出实验过程中利用光学滤波器和电子学滤波器来防止假线,同时兼顾信噪比的实验参数设置方法.经实验证实,这套方法是行之有效的.     

Direct Identification of the Carbon Skeleton of Organic Compounds using Double Quantum Coherence 13C-NMR Spectroscopy. The INADEQUATE Pulse Sequence

NMR spectroscopy plays an important part in the determination of the structures of organic compounds. The parameters of importance here are the chemical shifts of the ¹H and ¹³C nuclei and the spin-spin interactions both between ¹H nuclei and between ¹H and ¹³C nuclei. Couplings between ¹³C nuclei were almost completely neglected until a few years ago, since they were extremely difficult to observe because of the low natural abundance of ¹³C. However, it is these couplings which afford information directly on the carbon-carbon connectivities in the molecule. It is now possible to use a special NMR pulse sequence to make these couplings more readily visible: the result of using this sequence is a ¹³C-NMR spectrum from which the carbon skeleton concerned can be directly read off. Two-dimensional spectra in particular are very easy to evaluate. The pulse sequence involved, which bears the somewhat puzzling name INADEQUATE, produces double-quantum coherences from which the NMR signals of the coupled carbon nuclei can be obtained. In this article the principle of double-quantum coherence is described and a number of examples for the application of the INADEQUATE pulse sequences to problems in synthetic organic chemistry, biosynthesis and natural products chemistry are presented; in addition, the possibility of applying the INADEQUATE method to other nuclei is considered.     

傅里叶变换红外光声光谱法测定土壤中有效磷

以中国科学院封丘生态实验站长期定位实验区的土样为材料(68样),利用傅里叶转换红外光声光谱测定土壤有效磷:以Olsen-P为因变量,通过傅里转换红外光声光谱构建偏最小二乘法和人工神经网络模型,利用模型进行预测。结果表明,偏最小二乘法模型的相关系数(R2)为0.96,校正标准偏差为1.79mg/kg,验证标准偏差为5.25mg/kg;人工神经网络模型的校正系数为0.84,校正标准偏差为2.40mg/kg,验证标准偏差为5.43mg/kg。两种模型均可以用于土壤有效磷的预测,且偏最小二乘模型优于人工神经网络模型。该方法的特点是无需样品前处理,且测定对样品无破坏,为土壤有效磷的快速测定提供新的手段。     

用傅里叶变换红外光谱测定汽油有关性质

用傅里叶变换红外光谱仪（FTIR）,在1550－660cm^-1波数范围内,采用化学计量学的偏最小二乘法（PLS）,测定汽油的辛烷值（RON）、密度、馏程（50％、90％）、芳烃、烯烃等质量性质。 试验结果表明,实验室标准方法测定的真值和红外光谱预测值的相关性好,检验结果符合国家标准方法的再现性要求。     

傅立叶变换拉曼光谱和红外光谱鉴别塑料

用傅立叶变换拉曼光谱、衰减全反射红外光谱和近红外光谱结合OPUS/Ident软件对添加不同填料、不同助剂的塑料进行鉴别分类。结果表明:分子光谱结合化学计量学鉴别塑料是一种快速可靠的方法。其中拉曼光谱和衰减全反射红外光谱能够直接区分样品,而近红外光谱非常类似,不能直接区分。但是用OPUS/Ident软件中的W ard算法处理这3种光谱后,得到的树形图能够将样品准确分类。