共查询到20条相似文献,搜索用时 15 毫秒
1.
用紫外-可见光谱(UV-Vis spectroscopy)表征载有布洛芬(ibuprofen)和吡罗昔康(piroxicam)复方药物的聚甲基丙烯酸甲酯(PMMA)膜在磷酸盐缓冲溶液(PBS)中的释放过程, 观察两种药物在时间外扰下的释放情况. 随着时间的推移, 两种药物都保持了持久的释放. 同时, 通过二维紫外相关光谱(two-dimensional UV correlation spectroscopy)来进一步探究两种药物从PMMA膜内释放到缓冲溶液中的先后顺序, 推断出布洛芬与PMMA之间形成了一定的氢键相互作用, 导致释放速度变缓. 复方载药膜的红外光谱证明了这种相互作用的存在, 验证了二维紫外相关光谱在药物缓释领域的潜在应用价值. 相似文献
2.
Accelerate oxidative degradation of six vegetable oils was monitored using FTIR and FT-Raman spectroscopy. Two-dimensional correlation spectroscopy and multivariate curve resolution alternating least squares (MCR-ALS) were applied to the analysis of the data. The use of hetero-spectral two-dimensional correlation of FTIR and FT-Raman data allowed the use of well established band assignments to interpret less clearly assigned spectral features. With a moving window approach it was possible to obtain simplified two-dimensional correlation maps and to detect compounds evolving with different kinetic. Simultaneous analysis of the oxidation experiments of the six different oils monitored by both spectroscopic techniques was performed using MCR-ALS. Although a complete resolution of the data was not possible, the spectral changes occurring during the oxidative degradation of the oils were described with a five-component model. The two fundamentally different chemometric approaches lead to coincident results. 相似文献
3.
溶液中聚(N-异丙基-2-甲基丙烯酰胺)热相变可逆性的杂合二维相关红外光谱研究 总被引:1,自引:0,他引:1
基于聚(N-异丙基-2-甲基丙烯酰胺)(PNiPMA)在升温和降温两个过程中测得的变温红外光谱构筑样本-样本杂合二维相关(Hybrid 2D Correlation)光谱,揭示其在热诱导相变过程中初始组分的恢复程度、相转变温度以及转变速率等物理参数的可逆性. 相似文献
4.
红外光谱法对肉苁蓉径向不同部位的分析与评价 总被引:9,自引:0,他引:9
采用傅里叶变换红外光谱、二阶导数谱和二维相关红外光谱技术对肉苁蓉由表及里3个部位的药材粉末及其水提物和醇提物进行了分析与评价研究.结果表明,肉苁蓉不同部位的一维光谱非常相似,三者相似系数分别为0.9605,0.944和0.976;二阶导数谱中峰位和峰强的差异明显.1430~1700 cm-1范围内的二维相关谱中皮部自动峰有3个,而中部及髓部均为4个,更直观的反映出三者的差异.不同部位水提物和醇提物的分析结果进一步明确了肉苁蓉皮部芳香类、环烯醚萜类及糖苷类物质与中部和髓部存在明显不同,而髓部的水溶性多糖、半乳糖醇和苯乙醇苷类物质均高于其它部位.可见红外光谱法结合二维相关红外光谱技术为同种药材不同部位的细微差异分析和评价提供了一种快速、全面和客观的方法和手段. 相似文献
5.
A wine fermentation has been monitored on a daily basis by (1)H NMR spectroscopy. Following data pre-processing that includes synthesis of the spectra to ensure all peaks are of constant half-width, the series of spectra were examined using generalised two-dimensional correlation techniques. Synchronous and asynchronous data maps have been generated and employed to interpret the changes in the fermentation process as a function of time. The results illustrate the potential of high resolution NMR with multivariate data analysis as a tool for process monitoring and the manner in which two-dimensional correlation mapping can aid in data interpretation. 相似文献
6.
Mecozzi M Pietrantonio E Pietroletti M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,71(5):1877-1884
In this paper the marine organic matter soluble in an alkaline medium called extractable humic substance (EHS), was extracted from three sediment samples of Tyrrhenian Sea and separated by precipitation at pH 2 in the two fractions of fulvic acids (FAs) and humic acids (HAs). FAs were further fractionated in seven sub-samples of different molecular weight (mw) by means of seven different ultrafiltration membranes operating in the range between mw<1 kDa and mw>100 kDa. Then the qualitative composition of each sample of fractionated FAs and HAs was studied by means of one-dimensional Fourier transform infrared spectroscopy in reflectance mode (FTIR-DRIFT) and by two-dimensional (2D) correlation spectroscopy both in wavelength-wavelength (WW) and in sample-sample (SS) mode. The application of 2D correlation WW spectroscopy allows to elucidate the different roles played by carbohydrates and proteins with respect to some lipid compounds such as fatty acids and ester fatty acids during the process of aggregate formations from mw approximately 1 kDa to higher size aggregates. In addition, 2D correlation WW spectroscopy allows to observe some peculiar interactions between carbohydrates and proteins in the formation of EHS aggregates, interactions which vary from a sample to another sample. The results of 2D correlation SS spectroscopy confirm the general evidences obtained by 2D WW spectroscopy and moreover, they also describe the formation of EHS aggregates as a complex process where evolutionary links and connectivity between aggregates of neighbour molecular size ranges are not evident. Two-dimensional correlation spectroscopy applied to FTIR spectroscopy shows to be a powerful tool for the investigation of the mechanisms involved in EHS aggregation because it supports the acquisition of structural information which sometimes can be hardly obtained by one-dimensional FTIR spectroscopy. 相似文献
7.
Chemical differences of the extractives revealed by FTIR methods can be further confirmed by 1H NMR and 13C NMR. Meanwhile, the volatile compounds in the extractives can be identified by GC/MS 相似文献
8.
9.
Surinder K. Mehta Yosuke Imai Hiroki Takumi Kinue Shibata Hiroyasu Sakamoto Takanori Takiue Hiroki Matsubara Makoto Aratono 《Colloid and polymer science》2013,291(11):2647-2652
The temperature-dependent conformational states of a monolayer film of ethylene glycol monododecyl ether (C12E1) at the air/water interface have been investigated using ellipsometry, surface tension, external reflection–absorption FTIR spectroscopy and two-dimensional infrared (2DIR) correlation analysis. The ellipticity coefficients and the entropy associated with C12E1 adsorption changed almost discontinuously at certain temperatures, which manifested the interfacial phase transitions. The phase transition and coexistence of two phases were further clarified using 2DIR correlation analysis with temperature perturbation. The asynchronous correlation maps revealed that both bands of asymmetric and symmetric C–H stretching vibration in one-dimensional IR were split into two components, which confirmed the coexistence of two phases at the interface. 相似文献
10.
11.
Osmani Q Hughes H Flavin K Hedin-Dahlstrom J Allender CJ Frisby J McLoughlin P 《Analytical and bioanalytical chemistry》2008,391(4):1229-1236
A detailed investigation into the functional groups responsible for the formation of a noncovalent complex between 2-aminopyridine
(template) and methacrylic acid (functional monomer) has been carried out using FTIR spectroscopy and confirmed by 1H NMR spectroscopic data. The approach adopted to confirm the mechanism of interaction was the analysis of the template plus
the structurally similar 2-methylaminopyridine and 2-dimethylaminopyridine. A 1:1 stoichiometry of complexation was determined
by Job plot analysis following titration, with FTIR results complementing those of the 1H NMR study. The strength of interaction between 2-aminopyridine and the functional monomer measured through band shifts by
FTIR spectroscopy was compared with such interactions for the isomers 3- and 4-aminopyridine. This comparison identified a
clear correlation between template pK
a, degree of interaction and subsequent nonspecific binding in the nonimprinted polymer. Using FTIR spectroscopy it was also
possible to observe the effect of temperature on the prepolymerisation solution. IR spectra showed that lower temperatures
led to more stabilized interactions of the hydrogen-bonded complex. The potential advantages of FTIR spectroscopy compared
with 1H NMR spectroscopy in studying prepolymerisation solutions have been identified. 相似文献
12.
《Analytical letters》2012,45(15):2560-2569
A new approach for discrimination of adulterated milk is reported using two-dimensional infrared (IR) correlation spectroscopy by multiway principal component analysis (MPCA) and least squares support vector machines (LS–SVM). First, the synchronous two-dimensional spectra of pure and adulterated milk were calculated. Then, MPCA was used to reduce the dimensions, extract features of two-dimensional correlation data set, and distinguish adulterated milk and pure milk. Finally, a LS-SVM model was developed using the scores of the first thirteen principal components from synchronous two-dimensional correlation spectra computed by MPCA as the input variables. The ratios of correct classification were 100% and 96.3% for calibration set and prediction set, respectively. The area under the receiver operating characteristic curves (ROC) of 0.991 for prediction set was obtained by LS–SVM. The results indicate that two-dimensional correlation infrared spectra combined with MPCA–LS–SVM may be a rapid screening technique for discrimination of adulterated milk with good accuracy. 相似文献
13.
Smith AW Chung HS Ganim Z Tokmakoff A 《The journal of physical chemistry. B》2005,109(36):17025-17027
We investigate the thermal denaturation of trpzip2 between 15 and 82 degrees C using two-dimensional infrared (2D IR) vibrational spectroscopy, dispersed vibrational echo (DVE) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The FTIR and DVE spectra of trpzip2 show in the amide I region of the spectrum two resonances, which arise primarily from the interstrand coupling between local amide I oscillators along the peptide backbone. The coupling is seen directly in the 2D IR spectra as the formation of cross-peak ridges. Although small shifts of these frequencies occur on heating the sample, the existence of cross-peak ridges at all temperatures indicates that stable hydrogen bond interactions persist between the two beta-strands. These observations indicate a significant amount of native structure in the thermally denatured state of trpzip2. 相似文献
14.
The effects of elevated hydrostatic pressure on four representative proteins, lysozyme, human serum albumin, ubiquitin and RNase A, were investigated by using Fourier transform infrared (FTIR) spectroscopy, by principal component analysis (PCA) and by moving-window two-dimensional (MW2D) correlation analysis. In addition, we revealed the pressure-induced changes of secondary structure elements using curve fitting. With pressure increase, the amide I band shifted to lower wavenumbers, with a transition at 200 MPa, which was indicative of hydration enhancement. Moreover, the pressure-induced behavior of pure water was studied, similar transition pressure was observed with protein in aqueous solution, suggesting that structure change of water around 200 MPa caused a hydration enhancement of protein. Under pressure higher than 200 MPa, the structural changes of the four proteins were obviously different except for the common features shifting to lower wavenumbers with pressure, basically due to the distinct structural differences among them. 相似文献
15.
Lehmann E Chmelik C Scheidt H Vasenkov S Staudte B Kärger J Kremer F Zadrozna G Kornatowski J 《Journal of the American Chemical Society》2002,124(29):8690-8692
Interference microscopy and FTIR microscopy are applied to study intracrystalline concentration profiles of methanol in CrAPO-5 zeolite crystals. By using both techniques, the high spatial resolution of interference microscopy is complemented by the ability of FTIR spectroscopy to pinpoint adsorbates by their characteristic IR bands. For the first time two-dimensional concentration profiles of an unprecedented quality are reported which show a nonhomogeneous distribution of adsorbate in zeolite crystal under equilibrium with the adsorbate vapor. These nonhomogeneous profiles are attributed to regular intergrowth effects in CrAPO-5. A possible internal structure of CrAPO-5 crystals is suggested. 相似文献
16.
Payam Kalhor Yan-Zhen Zheng Hamad Ashraf Bobo Cao Prof. Zhi-Wu Yu 《Chemphyschem》2020,21(10):995-1005
Deep-eutectic solvents (DESs) are regarded as alternative green solvents to ionic liquids. In this work we report the structural properties and hydrogen bonding (H-bonding) interactions of an aqueous DES system. The used DES, ethaline (ETH), is composed of choline chloride and ethylene glycol (EG) in 1 : 2 molar ratio. The investigations were carried out by FTIR spectroscopy combined with quantum chemical calculations. Excess spectroscopy and two-dimensional correlation spectroscopy (2D-COS) were used to explore the data in detail. The results showed that, upon mixing, ETH transforms to EG dimers and trimers and D2O clusters transform to various ETH-D2O complexes. Theoretical calculations show that water molecules insert between the anion and cation of ETH, break the strong doubly ionic Cl− … H−OCh+ H-bond, share charges of the ions and form H-bond with them, thus modulate the interaction properties of ETH. This study deepens our molecular-level understanding of the system and would shed light on its applications. 相似文献
17.
二维相关荧光光谱技术 总被引:2,自引:0,他引:2
从发展历史、计算方程、一般规则和特有性质等方面系统地介绍了近年来在二维相关荧光光谱技术方面的方法探索和应用进展。以不同的外扰方式,如浓度、激发波长、猝灭以及其他如pH等分类,举例阐述了二维荧光相关光谱的可操作性及其应用,并与普通一维荧光光谱比较,说明了二维荧光相关光谱技术的优势。 相似文献
18.
Karlsson D Anders Borg O Lunell S Davidsson J Karlsson HO 《The Journal of chemical physics》2008,128(3):034307
The UV photodissociation of bromo-3-fluorobenzene under collisionless conditions has been studied as a function of the excitation wavelength between 255 and 265 nm. The experiments were performed using ultrafast pump-probe laser spectroscopy. To aid in the interpretation of the results, it was necessary to extend the theoretical framework substantially compared to previous studies, to also include quantum dynamical simulations employing a two-dimensional nuclear Hamiltonian. The nonadiabatic potential energy surfaces (PES) were parameterized against high-level MS-CASTP2 quantum chemical calculations, using both the C-Br distance and the out-of-plane bending of the bromine as nuclear parameters. We show that the wavelength dependence of the photodissociation via the S0-->1pipi*-->1pisigma* channel, accessible with a approximately 260 nm pulse, is captured in this model. We thereby present the first correlation between experiments and theory within the quantitative regime. 相似文献
19.
Toja F Nevin A Comelli D Levi M Cubeddu R Toniolo L 《Analytical and bioanalytical chemistry》2011,399(9):2977-2986
The preservation of design object collections requires an understanding of their constituent materials which are often polymeric
blends. Challenges associated with aging of complex polymers from objects with an unknown physical history may compromise
the interpretation of data from analytical techniques, and therefore complicate the assessment of the condition of polymers
in indoor museum environments. This study focuses on the analysis of polymeric materials from three well-known Italian design
lamps from the 1960s. To assess the degree of chemical modifications in the polymers, non-destructive molecular spectroscopic
techniques, Fourier-transform infrared (FTIR) and fluorescence spectroscopy, have been applied directly on the object surfaces
using an optical fiber probe and through examination of micro samples. FTIR spectra of the different polymers, polyvinylacetate
(PVAc) for the lamps Taraxacum and Fantasma, and both acrylonitrile–butadiene–styrene polymer (ABS) and cellulose acetate
(CA) for the lamp Nesso, allowed the detection of ongoing deterioration processes. Fluorescence spectroscopy proved particularly
sensitive for the detection of molecular changes in the polymeric objects, as the spectra obtained from the examined lamps
differ significantly from those of the unaged reference materials. Differences in fluorescence spectra are also detected between
different points on the same object further indicating the presence of different chemical species on the surfaces. With the
aid of complementary data from FTIR spectroscopy, an interpretation of the emission spectra of the studied polymeric objects
is here proposed, further suggesting that fluorescence spectroscopy may be useful for following the degradation of historical
polymeric objects. 相似文献