Computer-assisted multicomponent spectral analysis with fuzzy data sets

A new approach to the interpretation of spectra with “fuzzy sets” is described. A computer program CIF (Compound Identification with Fuzzy sets) is applied. This program is capable of finding components in a mixture by comparing the sample spectrum with reference spectra in a library. The applications discussed involve the interpretation of infrared spectra. The problems of spectral library search are discussed, an elementary introduction to fuzzy set theory is given, and applications to spectral library search are demonstrated.     

Decoding complex multicomponent chromatograms by fourier analysis

Summary The present work discusses the many attributes—classified as observable, intrinsic or hidden—which can be conceived for any complex multicomponent chromatogram. Discussion ensues on how to decode such chromatograms, i.e. determining the intrinsic and/or hidden attributes from those which can be observed. There are two main steps. The first is based on Fourier Analysis (FA) and determines the intrinsic attributes: i.e., the number of single components which can be detected; their distribution over the available chromatographic space and peak capacity. The second evaluates the hidden attributes: i.e., the effects of incomplete separation, the number of peaks created by one or more single components as well as their degree of purity. The hidden attributes can be obtained by applying the theory of Statistical Degree of peak Overlapping (SDO) and the paper goes into the extent to which the SDO step depends on the FA results. In addition, the role Exponential distribution plays as a point of reference for the distribution of both single component peak position interdistances and peak heights is discussed. Finally, a simplified graphical FA procedure is presented and the main achievements in this field are reviewed. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

板蓝根颗粒中蔗糖含量的红外光谱法测定

A method for rapid quantitative determination of sucrose in isatis-root granules by Fourier Transform Infrared Spectrophotometry(FTIR) was developed. Potassium ferricyanide was chosen as an inside mark material because it has only one strong absorption peak at 2117cm-1 and the peak was chosen as its quantitative peak. The peak at 1283cm-1 is the characteristic absorption of sucrose and was chosen as the quantitative peak of sucrose. The ratio of the two absorbances is I=Ai/As.K3[Fe(CN)6] and sucrose were mixed according to a certain mass ratio m=mi/ms to prepare standard samples. The curve of m versus I is the quantitative working curve. The linear range for sucrose is 5.0～23.0mg/g,the recovery is in the range of 91%～103%,the relative standard deviation is less than 5%.     

The destruction-free analysis of polymers by fourier transform infrared photoacoustic and fourier transform Raman spectroscopy: A comparison

With the introduction of rapid–scanning Fourier transform infrared (FTIR) and recently Raman (FT–Raman) spectroscopy, vibrational spectroscopy has been launched into a new era of applications in polymer chemistry and physics. Thus, the increase in sensitivity provided by multiple scanning has led to the breakthrough of new, destruction–free sampling techniques, such as photoacoustic and Raman spectroscopy. This paper provides a comparison between data produced by FTIR photoacoustic and FT–Raman analysis of a range of polymers, and structural information available from both techniques is discussed.     

TGA/FT-IR: Thermogravimetric analysis with fourier transform infrared detection of evolved gases

Thermogravimetric analysis (TGA) is a widely employed technique for measuring the change in weight of a sample as a function of temperature or time in a controlled atmosphere. FT-IR has been utilized with success in the identification of gases [1]. The combination of these two techniques permits a complete characterization of materials in terms of thermal stability and decomposition mechanisms [2]. A complete integrated system for TGA/FT-IR analysis is described.     

Flow injection analysis with fourier transform infrared detection for clinical and process analysis

As the analysis of glucose and urea is of special interest in the field of clinical and process analysis, an enzymatic FIA-FTIR system is presented, based on the reactions of glucose to gluconic acid using glucose oxidase as well as of urea to ammonium carbonate catalyzed by urease. The method is tested with standard solutions, with samples simulating the blood composition and with a variety of fruit juices and soft drinks. Whereas the systematic error is within few percent, as concluded from the slope of the calibration graph, the reproducibility of the method is up to now not satisfactory for routine applications in process analysis and has to be improved.     

Determination of sucrose by flow injection analysis with fourier transform infrared detection

A new methodology for the determination of sucrose in complex aqueous matrices by flow injection analysis with FTIR detection is presented. The methodology based on the enzymatic hydrolytic cleavage of sucrose by means of invertase to -D-glucose and -D-fructose. A special manifold consisting of two internally coupled injection valves being switched simultaneously is applied to facilitate recording FTIR spectra of the sample before and after the enzymatic reaction. The analytical readout is taken from the resulting difference spectrum obtained by subtracting the FTIR spectra of the sample before and after the reaction. The developed methodology uses a GC-IR software to continuously record the FTIR spectra of the effluent from the manifold. The proposed method gives linear results in the range of 10 to 100 mmol/l and has been successfully applied to the analysis of sucrose in synthetic mixtures as well as in real samples such as soft drinks.     

Fourier transform raman spectroscopy using a bench-top fourier transform infrared spectrometer

The use of a bench top FTIR spectrometer for near infrared Fourier transform Raman spectroscopy is demonstrated. The use of near infrared excitation results in fluorescence free Raman spectra allowing previously difficult samples to be measured.     

Application of multicomponent spectrophotometry in analysis of copper electroplating bath solutions

Multiwavelength multicomponent analysis for copper and nickel is explored within the spectral range 230-900 nm in order to enable copper (?0.2 g l^?1) and nickel to be determined simultaneously even at high (20 l^?1) and nickel concentrations in industrial electroplating baths. Calibration based on pure-component spectra is compared to multivariate calibration based on data reduction with principal component analysis with the partial least-square algorithm. By use of multivariate calibration techniques, sulphuric acid can also be determined indirectly by its effect on the absorbance of the metal ions. The performance of the method is evaluated for different spectral ranges and the experimental results are related to the selectivity of the different systems quantified by the condition number of the actual absorptivity matrix.     

高灵敏度高选择性多组分痕量分析研究:卡尔曼滤波-分光光度法

本文根据卡尔曼滤波算法结合高灵敏显色反应提出了一种新的高灵敏度高选择性多组分痕量分析方法, 对卡尔曼滤波处理过程, 估计初值, 新息序列, 信息增量等作为分析结果评价, 波长数目选择的依据等基础性理论问题进行了探讨, 应用于十余种高灵敏显色反应体系, 对多种金属离子混合物及实际样品进行同时或分别测定, 可不经任何分离, 操作简便, 结果良好。     

Conformations of seven-membered rings: the fourier transform model

A representation of the puckered conformations of seven-membered rings, using the Fourier Transform model and derived from the torsion angles, is presented in terms of two puckering amplitudes and their corresponding puckering phases. p]These four parameters are used to describe the main conformational types and to study the planarity of the rings, symmetrical forms, pseudorotation pathways and symmetrical interconversions through the puckering levels. This analysis provides a criterion for characterizing the basic conformations which have already been established by earlier work. A comparison with previous models is also given and the representation applied to some 1,4-benzodiazepine compounds.     

Combined thermogravimetry and fourier transform infrared spectroscopy techniques for gas evolution analysis

The usefulness of thermogravimetry has been amply demonstrated for a wide variety of material analysis applications. In many instances, however, additional information is required for adequate characterization of the sample and its thermal decomposition behaviour. In this respect, the analysis of evolved gases, or condensed liquids, has proven a highly useful approach. Among the various physical methods used for analysis of the thermal degradation products, infrared spectroscopy has often been found very powerful, being versatile, rapid and widely accessible. In this study, we report a simple new approach in which the evolved gases and condensed liquids from the thermal decomposition of various products are recuperated in an infrared gas cell and on a PVC membrane filter, respectively. The gaseous components were analysed by transmission FT-IR, and the condensed liquid products were examined directly on the PVC membrane by FT-IR in the internal reflexion mode. The technique was used, for example, to examine the pyrolysis products (gases and liquid) of Koberit, a proposed substitute for asbestos. The method was also applied to the study of chemically derivatized asbestos materials in an attempt to unravel the surface chemical modifications.     

Assessment of local analysis by fourier transform laser microprobe mass spectrometry with external ion source

Laser microprobe mass spectrometry (LMMS) is a technique for local analysis of inorganic and organic constituents in the m range. This paper will focus on selected applications. First of all, element detection is illustrated by data from a 50-nm TiW layer on silicon and by the detection of residual Cr on HPLC column packing material. Speciation capabilities of LMMS are demonstrated on pure substances and on a coated neo-ceramic. Finally, the feasibility of organic analysis is shown in the case of a biologically active compound and dyed cloth fibres.     

涂石蜡大米傅立叶变换红外吸收光谱识别分析

针对11种未涂石蜡大米和18个涂不同量石蜡的大米样品,以石油醚提取的油脂为试样,采用傅立叶变换红外光谱仪,扫描样品的傅立叶变换红外吸收光谱,并对光谱进行预处理,提取红外特征信息,将2855与1746、1462与1163 cm-1处特征峰的面积比值为坐标,采用Origín 6.0软件作识别分类图.结果表明:特征峰的面积比值与所涂石蜡量成线性变化,大米油脂的特征峰面积比值在一定的区域分布,涂以0.05%以上石蜡的大米,其油脂特征峰面积比值与未涂石蜡米油脂的值有一定区别.     

Feature analysis of protein structure by using discrete Fourier transform and continuous wavelet transform

In this paper, discrete Fourier transform (DFT) and continuous wavelet transform (CWT) are used to predict the protein structure. Hydrophobicity plays a key role in the form of protein structure. The amino acid sequence is first mapped into hydrophobicity sequence, and then process it by DFT and CWT so that power spectral density is gained. The results show that continuous wavelet transform can extract the features of protein structure effectively and availably and has a tremendous development foreground.     

Determination of electron transfer kinetic parameters by fourier transform electrochemical impedance spectroscopic analysis

A new attempt to obtain electron transfer kinetic parameters at an electrified electrode/electrolyte interface using Fourier transform electrochemical impedance spectroscopic (FTEIS) analyses of small potential step chronoamperometric currents is presented. The kinetic parameters thus obtained allowed mass transport free voltammograms to be constructed in an overpotential region, where the diffusion limits the electron transfer reaction, using the Butler-Volmer (B-V) relation. The B-V voltammograms clearly distinguish electrode reactions that are not much different in their electron transfer kinetic parameters, thus showing very similar normal linear sweep voltammetric (SCV) behaviors. Electrochemical reduction of p-benzoquinone, which displays nearly the same SCV responses at a gold electrode regardless whether the electrode is covered by a thiolated beta-cyclodextrin self-assembled monolayer, was taken as an example for the demonstration. The results show that the two voltametrically similar systems display very different electron transfer characteristics.     

Attenuated total reflectance fourier transform infrared analysis of fly ash geopolymer gel aging

Structural changes in fly ash geopolymers activated with different sodium hydroxide and silicate concentrations are investigated using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy over a period of 200 days. A strong correlation is found between the concentration of silicate monomer in the activating solution and the position of the main Si-O-T stretching band in the FTIR spectrum, which gives an indication of the relative changes in the gel Si/Al ratio. The FTIR spectra of geopolymer samples with activating solution concentrations of up to 1.2 M SiO2 indicate that an Al-rich gel forms before the final gel composition is reached. The time required for the system to reach a steady gel composition depends on the silicate activating solution concentration and speciation. Geopolymers activated with solutions containing predominantly high-order silicate species rapidly reach a steady gel composition without first forming an Al-rich gel. A minimum silicate monomer concentration of approximately 0.6 M is required to shift the geopolymer synthesis mechanism from hydroxide activation to silicate activation. Silicate speciation in the activating solutions also affects zeolite formation and geopolymer microstructures, with a more homogeneous microstructure and less zeolite formation observed at a higher SiO2 content.     

自动调节光谱响应的高精度多组分分析研究: 人工神经网络分光光度法

本文论证了人工神经网络(ANN)对多组分光度分析的应用。探讨了人工神经网络算法及其影响因素。用此法做五组分体系(维生素B1, B2, B6, C和菸酰胺)紫外光度分析, 并与CPA方法作比较。该方法的特点在于可由调节不同光谱范围的线性及非线性响应的计算过程来自动校正。研究结果证实了该方法的优越性。     

Quantitative analysis by nuclear magnetic resonance with fourier transform II?13C resonance

Quantitative analyses have been carried out by ¹³C NMR spectroscopy using Fourier transformation. The Overhauser effect, due to the broad band decoupling of protons, has been suppressed using the two existing methods (gated decoupling and paramagnetic species), and results from each are compared. Both require a calibration curve, and the second method, when applied to aromatic substances, needs the ratio between the sample to be analysed and the paramagnetic species to be less than a certain value. Experiments have been made with pure products and blends of pure products containing both saturated and aromatic carbons. The precision of the results is given.