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。     

二维相关红外光谱法与阿胶的真伪鉴别

采用傅里叶变换红外光谱法(FT-IR)和二维相关红外光谱技术(2D-IR)对几种阿胶进行了真伪鉴别。实验结果表明,伪品阿胶和黄明胶与标本东阿阿胶的谱图较为相似,尤其是黄明胶与阿胶极其相似,仅仅在1648cm^-1的酰胺I带的吸收峰和东阿阿胶有9个波数的区别;不同批次和厂家的正品阿胶的红外光谱图更为相似,难以区分开,借助于二维相关红外光谱法,获取了物质的微观结构信息,提高了谱图的分辨率,几种真品阿胶得到了直观有效的鉴别。     

二维相关红外光谱与奶粉的品质分析

采用红外光谱法(FT-IR)并结合二阶导数谱对几种奶粉产品进行了无损快速鉴别。结果表明：不同脂肪含量的奶粉其最主要的差别直观地表现在1747cm^-1对应的脂肪C=O吸收峰强度的不同;同理,不同糖含量的奶粉红外谱图上的主要差别就体现在糖的特征峰带(1150—900cm^-1)的强度上。最后,采用二维相关红外光谱法(2D-IR)对全脂奶粉和全脂甜奶粉进行了热扰动过程研究,发现由于糖类物质的加入,奶粉蛋白成分在常温下变得相对稳定。该法为研究奶粉的稳定性提供了一条新的途径。     

傅里叶变换红外光谱法检测脑肿瘤

应用傅里叶变换红外光谱法检测了28例液氮冻存的离体脑肿瘤样本及其残留物(将脑肿瘤样本从ATR的ZnSe晶片上取下,样本在ZnSe晶片上沾染后留下的物质).结果发现,神经鞘瘤和神经上皮组织肿瘤(如星形细胞瘤等)的主要特征吸收峰存在明显差异,因此可从各个特征吸收峰的峰位、峰形及不同谱峰强度比的变化来初步鉴别脑肿瘤的性质,脑肿瘤组织样品残留物的红外光谱也可反映不同性质脑肿瘤的差异.与脂类糖蛋白以及核酸相关的谱带变化分析表明,通过特征峰强比(I1460cm-1/I1400cm-1,I1160cm-1/I1120cm-1和I1160cm-1/I1080cm-1)来鉴别肿瘤的性质与病理诊断结果的符合率超过85%.     

钛硅分子筛挤条成型催化剂热稳定性能的研究

采用在空气中程序升温焙烧的方式考察了钛硅分子筛挤条成型催化剂的热稳定性能．对不同温度焙烧得到的样品进行了XRD、IR、UV Raman和SEM表征．结果表明，在高温焙烧时，由于载体结构的改变引起载体与分子筛之问相互作用发生变化，导致成型催化剂中分子筛骨架破坏．随着焙烧温度的提高，IR谱图中960cm^-1处代表钛进入骨架的特征峰的强度迅速减弱，当焙烧温度达到1000℃时，960cm-1处的骨架钛特征峰移至948cm^-1．在紫外拉曼谱图中，骨架位钛物种的特征拉曼谱峰-1125cm^-1谱峰在加入SiO2载体后，高温下峰强度明显降低，这说明载体的加入降低了钛硅分子筛挤条成型催化剂的热稳定性能．     

不同产地黄芪的红外光谱鉴别研究

采用红外光谱、二阶导数红外光谱和二维相关红外光谱,对四种不同产地的黄芪原药材进行了鉴别研究。结果表明:不同产地黄芪的红外光谱和二阶导数红外谱具有一定的相似度,与淀粉的红外谱图比对,4个不同产地的黄芪均含有淀粉,其中陕西绥德产黄芪的淀粉含量比其它3个产地黄芪的都要高。山西浑源和山西天镇产黄芪谱图的1 510、1 425cm-1木质素特征峰比内蒙古固阳和陕西绥德产黄芪的更为明显,说明前二者产黄芪中木质素含量高于后二者产黄芪。在二维相关红外谱图上,根据4个产地黄芪的相对峰强度的差异,可进行产地的鉴别。研究结果表明对于不同产地黄芪的鉴别,红外三级鉴定法是一种快速有效的新方法。     

二维傅里叶变换红外(2D FTIR)相关光谱技术研究聚羟基丁酸酯(PHB)的熔融与结晶

应用新型二维傅里叶变换红外（2D FTIR）相关光谱研究细菌合成聚羟基丁酸酯（PHB）在升温时的预熔行为以及降温后的重结晶过程。在25－220℃的变温过程中测得动态红外光谱。着重讨论了在热力学干扰导致红外谱图中羰基峰（1700－1770cm^-1)和醚键（1230－1310cm^-1）吸收强度的波动。结果表明，这种影响来自样品中PHB的结晶态和非晶态之间的相态变化。二维谱图分析表明，在热熔过程中，结晶态的消失并不同时引起完全非晶态的出现，暗示在分子排列高度有序的晶态和非晶态之间存在某种中间态，PHB晶体向非晶态转变时必须经过一个预熔过程。在红外谱图上这个中间态很可能对应着由二维分析显示出来的位于1730cm^-1的吸收峰。同时，在PHB熔体从非晶态逐渐生成晶体的过程中也探测到了中间态的存在。     

固态多环芳烃化合物的THz时域光谱研究

利用太赫兹时域光谱技术室温下对芳烃化合物萘、联苯、葸、α-萘酚和β-萘酚在3-73cm^-1(0．1．2．2THz)频谱范围内进行了光谱测量。结果表明，多环芳烃化合物在此波段有不同的吸收特征。不能形成氢键的萘、联苯和蒽在67cm^-1(2．0THz)附近均有一吸收峰，这可能是由于分子之间的振动即晶格振动所引起的；而能够形成氢键的口一萘酚和卢．萘酚，其吸收峰可归结于分子间氢键的相互作用所引起的集体振动模式。1Hz时域光谱不仅能够鉴别分子结构存在微小差别的化合物而且还能鉴别同分异构体。     

松杉灵芝不同部位的红外光谱分析研究

采用红外光谱三级鉴定法对松杉灵芝菌盖、表皮、菌柄、子实体不同部位的红外光谱图进行了整体分析。结果表明:松杉灵芝的各部位均含萜类、甾醇类、氨基酸、多肽、蛋白质和糖苷类等物质。在松杉灵芝的一维红外光谱中,菌盖的1 649cm-1峰的相对强度明显比表皮、菌柄和子实体强,说明菌盖中所含的氨基酸、多肽、蛋白质物质的量比其它部位高;在二阶导数谱中,四者在1 720~1 600cm-1范围内峰形差别较大,进一步说明松杉灵芝不同部位所含氨基酸、多肽、蛋白质物质不一致;而二维相关红外光谱中,各部位自动峰的数目、峰位置和峰相对强度都有所不同,可推断松杉灵芝各部位本身所含的糖苷类物质是不一致的。     

大黄的傅里叶变换红外光谱法快速鉴别

利用傅里叶变换红外(FTIR)光谱法对不同的大黄药材进行了分析?结果表明：大黄样品在4000～1800cm^-1区域有相似的红外光谱特征,而在1800～400cm^-1区域不同组系、不同品种的样品又存在很大差异。因此红外光谱法可以快速、简便、直观地对中药材进行质量鉴别。     

Application of two-dimensional near-infrared correlation spectroscopy to the discrimination of Chinese herbal medicine of different geographic regions

Fructus Lycii is a traditional Chinese medicinal herb. The objective of this paper was to apply two-dimensional (2D) near-infrared (NIR) correlation spectroscopy to the discrimination of Fructus Lycii of four different geographic regions. Generalized 2D-NIR correlation spectroscopy was able to enhance spectral resolution, simplify the spectrum with overlapped bands, and provide information about temperature-induced spectral intensity variations that was hard to obtain from one-dimensional NIR spectroscopy. The 2D synchronous and asynchronous spectra showed remarkable differences within the range of 4950-5700cm(-1) between samples of different geographic regions. Using NIR instead of IR made the 2D approach more convenient and fast, and it can be applied to more area like process control. This approach can also be applied analogously to the discrimination of other Chinese herbal medicine of different geographic regions.     

Surface phase transition of C12E1 at the air/water interface: a study by dynamic surface tension, external RA FT-IR, and 2D IR correlation methods

The surface conformational states of the Gibbs monolayer of ethylene glycol mono-n-dodecyl ether (C(12)E(1)) at the air/water interface was studied using dynamic surface tension, external reflection-absorption FT-IR spectroscopy (ERA FT-IR), and two-dimensional infrared (2D IR) correlation methods at constant temperature. The dynamic surface tensions were measured at different bulk concentrations of C(12)E(1), and it was observed that a constant surface tension region appears at approximately 38.5 mN m(-1) in a dynamic surface tension profile at concentrations higher than 11 micromol kg(-1). This constant surface tension region corresponds to the surface phase transition from liquid expanded (LE) to liquid condensed (LC). Two sets of ERA FT-IR spectra were collected, one at different bulk concentrations but after equilibrium time (equilibrium measurements) and another at constant bulk concentration (m = 16 micromol kg(-1)) but at different times (dynamic measurements). The first set of these measurements show that the peak area increases in the range of 11 < m < or = 16 micromol kg(-1), which means the increase in the number of surfactant molecules at the air/water interface. Also, the wavenumber of antisymmetric CH(2) stretching decreases gradually from approximately 2923 cm(-1) (for 10 and 11 micromol kg(-1)) to approximately 2918 cm(-1) (for m > or = 16 micromol kg(-1)) with increasing concentration. The wavenumbers of 2923 and 2918 cm(-1) were assigned to LE and LC phases, respectively, and the decrease of wavenumber in the concentration range of 11 < m < or = 16 micromol kg(-1) were correlated to the surface phase transition (LE --> LC), or in other words, in the mentioned concentration range, two phases coexist. The dynamic ERA FT-IR measurements at 16 micromol kg(-1) also confirm the surface phase transition from LE to LC. The 2D IR correlation method was applied to the both equilibrium and dynamic IR spectra of the C(12)E(1) monolayer. The synchronous correlation maps show two strong autopeaks at approximately 2922 and approximately 2851 cm(-1) and also show a strong correlation (cross-peaks) between antisymmetric CH(2) stretching (nu(a)) and symmetric CH(2) stretching (nu(s)). The asynchronous correlation maps show that both observed bands of nu(a) and nu(s) in one-dimensional IR split into two components with the characteristic of overlapped bands, which reveals the coexistence of two phases (LE and LC) at the interface at 11 < m < or = 16 micromol kg(-1). The synchronous and asynchronous maps that were obtained from dynamic IR spectra closely resembled the equilibrium map.     

Ab initio-based all-mode two-dimensional infrared spectroscopy of a sugar molecule

To construct two-dimensional infrared (2D IR) spectra having all vibrational modes of a molecule included is still quite challenging, both experimentally and theoretically. Here we report an ab initio-based all-mode 2D IR spectra simulation approach. Using deuterated glycolaldehyde (CH2OHCDO), the smallest sugar as a model molecule, we have calculated correlation 2D IR spectrum of its entire 3N-6 (N=8) normal modes in the mid-to-far-IR region (4000-0 cm(-1)), using quantum chemical anharmonic frequency and anharmonicity computations in conjunction with time-domain third-order nonlinear response functions. The calculated 2D IR spectra were found to contain a network of structural and dynamical parameters of the molecule. It is found that certain spectral regions, once enlarged, show features that are in reasonable agreement with limited but already available single- and dual-frequency 2D IR experimental results. The extension of narrow-band 2D IR spectroscopy into the full mid-to-far-IR regime would allow us to characterize the structural distributions and dynamics of molecular complexes in condensed phases with sufficient number of parameters.     

Fast quality control of Herba Epimedii by using Fourier transform infrared spectroscopy

Herba Epimedii is a well-known traditional Chinese medicine (TCM) having the effect of nourishing the kidney and strengthening the 'Yang'. Its primary effective constituents are considered to be the 8-prenyl flavonols, which can be assorted into 4'-methoxyl-prenylflavonols (MPFs) and 4'-hydroxyl-prenylflavonols (HPFs), according to the group (methoxyl or hydroxyl) located at 4' in their structures. The Fourier transform infrared spectroscopy (FT-IR) has been widely used in the researches of TCMs. In the present study, the FT-IR was attempted to be applied in the quality control of Herba Epimedii. We compared the IR spectra of 17 pure flavonoids, of which eight were derived from Herba Epimedii, and found a characteristic absorption peak at 1259+/-1 cm(-1), corresponding to the MPFs, the major 8-prenyl flavonols in the aerial parts of the Epimedium species. This peak could also be found in the IR spectra of both the herbal samples and their 70% ethanol extracts. Moreover, the intensity of this peak was in the direct correlation with the total content of MPFs. The correlation values, representing the semblance of two spectra, of the IR spectrum of herbal sample and icariin, in the range of 1280-1200 cm(-1), had been established to be a good index for the quality control of the herbs. Accordingly, a correlation value of not less than 0.50 could be used as the essential screening criteria for the herbs. The FT-IR could be used for the fast and effective quality control of Herba Epimedii.     

Research on processing medicinal herbs with multi-steps infrared macro-fingerprint method

How to apply rapid and effective method to research medicinal herbs, the representative of complicated mixture system, is the current study focus for analysts. The functions of non-processed and processed medicinal herbs are greatly different, so controlling the processing procedure is highly important for guarantee of the curative effect. Almost, the conventional criteria of processing are based on personal sensory experience. There is no scientific and impersonal benchmark. In this article, we take Rehmannia for example, conducting a systematic study on the process of braising Rehmannia with yellow wine by using the multi-steps infrared (IR) macro-fingerprint method. The method combines three steps: conventional Fourier transform infrared spectroscopy (FT-IR), second derivative spectroscopy, and two-dimensional infrared (2D-IR) correlation spectroscopy. Based on the changes in different types of IR spectra during the process, we can infer the optimal end-point of processing Rehmannia and the main transformations during the process. The result provides a scientific explanation to the traditional sensory experience based recipe: the end-point product is "dark as night and sweet as malt sugar". In conclusion, the multi-steps IR macro-fingerprint method, which is rapid and reasonable, can play an important role in controlling the processing of medicinal herbs.     

IR plus vacuum ultraviolet spectroscopy of neutral and ionic organic acid molecules and clusters: acetic acid

Infrared (IR) vibrational spectroscopy of acetic acid (A) neutral and ionic monomers and clusters, employing vacuum ultraviolet (VUV), 10.5 eV single photon ionization of supersonically expanded and cooled acetic acid samples, is presented and discussed. Molecular and cluster species are identified by time of flight mass spectroscopy: the major mass features observed are A(n)H(+) (n=1-9), ACOOH(+) (VUV ionization) without IR radiation present, and A(+) with both IR and VUV radiation present. The intense feature ACOOH(+) arises from the cleavage of (A)(2) at the beta-CC bond to generate ACOOH(+)+CH(3) following ionization. The vibrational spectrum of monomeric acetic acid (2500-7500 cm(-1)) is measured by nonresonant ionization detected infrared (NRID-IR) spectroscopy. The fundamentals and overtones of the CH and OH stretches and some combination bands are identified in the spectrum. Mass selected IR spectra of neutral and cationic acetic acid clusters are measured in the 2500-3800 cm(-1) range employing nonresonant ionization dip-IR and IR photodissociation (IRPD) spectroscopies, respectively. Characteristic bands observed at approximately 2500-2900 cm(-1) for the cyclic ring dimer are identified and tentatively assigned. For large neutral acetic acid clusters A(n)(n>2), spectra display only hydrogen bonded OH stretch features, while the CH modes (2500-2900 cm(-1)) do not change with cluster size n. The IRPD spectra of protonated (cationic) acetic acid clusters A(n)H(+) (n=1-7) exhibit a blueshift of the free OH stretch with increasing n. These bands finally disappear for n> or =6, and one broad and weak band due to hydrogen bonded OH stretch vibrations at approximately 3350 cm(-1) is detected. These results indicate that at least one OH group is not involved in the hydrogen bonding network for the smaller (n< or =5) A(n)H(+) species. The disappearance of the free OH stretch feature at n> or =6 suggests that closed cyclic structures form for A(n)H(+) for the larger clusters (n> or =6).     

Electron paramagnetic resonance, optical absorption and IR spectroscopic studies of the sulphate mineral apjohnite

Apjohnite, a naturally occurring Mn-bearing pseudo-alum from Terlano, Bolzano, Italy, has been characterized by EPR, optical, IR and Raman spectroscopy. The optical spectrum exhibits a number of electronic bands around 400 nm due to Mn(II) ion in apjohnite. From EPR studies, the parameters derived, g=2.0 and A=8.82 mT, confirm MnO(H(2)O)(5) distorted octahedra. The presence of iron impurity in the mineral is reflected by a broad band centered around 8400 cm(-1) in the NIR spectrum. A complex band profile appears strongly both in IR and Raman spectra with four component bands around 1100 cm(-1) due to the reduction of symmetry for sulphate ion in the mineral. A strong pair of IR bands at 1681 and 1619 cm(-1) with variable intensity is a proof for the presence of water in two states in the structure of apjohnite.     

Investigation of selective molecular interactions using two-dimensional Fourier transform IR spectroscopy

A novel method of studying molecular interactions is introduced. It is a method based on the framework of a two-dimensional (2D) infrared (IR) correlation spectroscopy technique with a new data pretreatment strategy. In this method, an additional external perturbation stimulates the system to cause some selective changes in the state, order, and surroundings of system constituents. The overall response of the stimulated system to the applied external perturbation leads to distinctive changes in the measured spectrum, and a series of perturbation-induced dynamic spectra are collected in a systematic manner. Such a set of dynamic spectra are then transformed into a set of 2D correlation spectra by cross-correlation analysis. Temperature was chosen as an external perturbation, and the molecular interaction between 4-aminopyridine (Apy) and methacrylic acid (MAA) was investigated by 2D IR correlation spectroscopy. Synchronous cross peaks exist between the stretching vibration of the C–O group of MAA at 1,298 and 1,202 cm⁻¹ and the C=N group of Apy at 1,531 cm⁻¹, and between the carbonyl group of MAA at 1,705 cm⁻¹ and the amino group of Apy at 3,382 and 3,212 cm⁻¹. The synchronous cross peaks are from orientation of MAA and Apy vibrations generated at the same time; the synchronization of microstructure movements in the molecules indicates that there exists strong interactions between MAA and Apy. According to 2D correlation rules, static electricity and hydrogen-bonding interactions exist between Apy and MAA. Such results were further verified by ¹H-NMR spectroscopy. The successful application demonstrates that 2D IR correlation spectroscopy may be a convenient and effective method in the study of molecular interactions.     

Infrared plus vacuum ultraviolet spectroscopy of neutral and ionic methanol monomers and clusters: new experimental results

We present new observations of the infrared (IR) spectrum of neutral methanol and neutral and protonated methanol clusters employing IR plus vacuum ultraviolet (vuv) spectroscopic techniques. The tunable IR light covers the energy ranges of 2500-4500 cm(-1) and 5000-7500 cm(-1). The CH and OH fundamental stretch modes, the OH overtone mode, and combination bands are identified in the vibrational spectrum of supersonic expansion cooled methanol (2500-7500 cm(-1)). Cluster size selected IR plus vuv nonresonant infrared ion-dip infrared spectra of neutral methanol clusters, (CH(3)OH)(n) (n=2,[ellipsis (horizontal)],8), demonstrate that the methanol dimer has free and bonded OH stretch features, while clusters larger than the dimer display only hydrogen bonded OH stretch features. CH stretch mode spectra do not change with cluster size. These results suggest that all clusters larger than the dimer have a cyclic structure with OH groups involved in hydrogen bonding. CH groups are apparently not part of this cyclic binding network. Studies of protonated methanol cluster ions (CH(3)OH)(n)H(+) n=1,[ellipsis (horizontal)],7 are performed by size selected vuv plus IR photodissociation spectroscopy in the OH and CH stretch regions. Energies of the free and hydrogen bonded OH stretches exhibit blueshifts with increasing n, and these two modes converge to approximately 3670 and 3400 cm(-1) at cluster size n=7, respectively.     

Hematite and carbonaceous materials in geological samples: a cautionary tale

Over the last few decades Raman spectroscopy has been increasingly applied as an analytical tool in geoscience research. Raman spectroscopy is a powerful tool for geologists as it is non-destructive, requires little to no sample preparation, and can be undertaken in situ on various irreplaceable geological samples. Also, this technique is useful in the identification of minerals and geo-organic material. However, despite this ease of application, there are some facets of Raman spectroscopy data that can lead to erroneous interpretations. For instance, there is much confusion in the geological literature distinguishing the difference between the hematite vibrational mode at ca. 1320 cm(-1) and the disordered sp(2) carbonaceous material D band at 1340 cm(-1). Furthermore, geologists will often collect 2 spectra, one in the mineral finger print region (200-800 cm(-1)) and then a spectrum in the carbon first-order region (1000-1800 cm(-1)), rather than performing a full-region scan. This allows the misidentification of the hematite mode at 1320 cm(-1) as the D band from disordered carbonaceous material. Here we show that it is best practice for geologists to collect spectra between 200 and 1800 cm(-1) to better distinguish between hematite and disordered carbonaceous material, materials that often co-occur in geological samples.