一种新的目标转换因子分析算法用于混合物红外光谱中纯组分光谱的解析

本文针对运用目标转换因子分析从混合物红外光谱中解析出纯组分光谱的有关限制,进行了有效的改进。把抽象正交特征光谱与以单一向量为初始向量的目标转换因子分析相结合,提出了一种新的算法,结果令人满意。     

一种新的目标转换因子分析算法用于混合物红外光谱中纯组分光谱的解析

本文针对运用目标转换因子分析从混合物红外光谱中解析出纯组分光谱的有关限制,进行了有效的改进.把抽象正交特征光谱与以单一向量为初始向量的目标转换因子分析相结合,提出了一种新的算法,结果令人满意.     

目标识别因子分析解析完全未知混合体系的研究

本文以目标识别因子分析为基础, 将因子分析与聚类分析相结合, 给出了从完全未知混合体系中提取纯物种光谱的新方法。所得纯物种光谱经光谱检索作定性判别, 然后利用外标法对混合物中的各组份进行标定。该方法用于计算机模拟体系及三组份实际混合体系的红外光谱解析, 结果令人满意。     

完全未知混合体系中纯组份的红外光谱解析

提出一种新的目标转化因子分析，其初始向量的构造基于实际最大差异光谱，无需分离即可从红外混合体系中解析出纯组份光谱。该算法简单易懂，不必迭代，运算量小，应用于模拟及实际体系，结果令人满意。     

完全未知混合体系的纯物种光谱辨析

基于因子分析的迭代目标转换算法,本文提出一种从完全未知混合物体系中获取纯物种光谱的解析方法。该法简单明了,不增加任何困难即可拓广至含n组份的混合体系,对光谱峰形状亦无任何附加限制要求。先采用计算机模拟技术对该法进行了校验,继用于紫外可见与荧光光谱的实际混合体系的解析,均获满意结果。     

完全未知混合体系的纯物种光谱辨析

基于因子分析的迭代目标转换算法,本文提出一种从完全未知混合物体系中获取纯物种光谱的解析方法.该法简单明瞭,不增加任何困难即可拓广至含n组份的混合体系,对光谱峰形状亦无任何附加限制要求.先采用计算机模拟技术对该法进行了校验,继用于紫外可见与荧光光谱的实际混合体系的解析,均获满意结果.     

免疫-遗传算法用于混合物重叠核磁共振信号解析

通过对免疫系统中抗体对外来抗原的识别、消除等过程的模拟,建立了一种新型的免疫算法模型.将标样信号作为抗体,混合物重叠信号作为抗原输入免疫算法模型,通过迭代运算,从抗原中消除抗体所表示的信息,当抗原被抗体完全消除时,即实现了混合物重叠信号的解析.对多组分混合氨基酸NMR谱图的解析结果证明,该算法可方便地用于多组分重叠信号的解析,为利用数据库解析混合物或生物大分子等物质的复杂NMR谱图开辟了一条全新的途径.     

基于计算最大差异光谱的目标转换因子分析用于解析混合物红外光谱

基于因子分析的目标转换法[1]利用抽象光谱构成的矩阵具有使纯物种光谱向自身逐步逼近的性质[2],用于混合物红外光谱的解析,简单明确[3]．在进一步的探索中,我们发现该算法对原始光谱的构成具有较强的依赖性．本文特别构造了这样的体系,即在混合物样品中剔除了某一物种占优势的样品,应用新算法后,避免了对采样的依赖性．1方法与原理根据自模拟曲线分辨算法（SelfModelingCurveResolution,SMCR）[4~6],纯物种光谱可写成式中,Akj为抽象正交光谱,Xik为系数,Fij为纯物种光谱,n为物种数．根据吸光度不能为负这一限制条件,可以…     

多组分体系红外光谱法矩阵分析

近年来用分光光度法结合电子计算机,对多组分混合物不经分离进行测定的方法发展较快。在无机多组分体系方面,有以线性规划法分析稀土元素混合物和用矩阵方法分析锰、锌混合物的研究。对有机多组分体系作者曾对三个相互干扰组分:阿斯匹林、非那西丁和咖啡因用线性规划法及坐标轮换法进行紫外光谱计算分析;胡鑫尧等则对此体系作了红外光谱计算分析研究,并提出了非线性规划     

大气开放光路傅里叶变换红外光谱的定性分析

通过目标波段熵最小化(BTEM)和目标因子分析(TFA)两种化学计量学方法研究了大气开放光路傅里叶变换红外(OP/FT-IR)光谱,从多组分测量数据重建特定目标分子的光谱特征,以实现对大气这种复杂体系的定性分析。在牧场周围完成了5次连续OP/FT-IR光谱测量,将光谱按照测量时间顺序排列,获得5个数据矩阵作为研究对象。结果表明,BTEM和TFA两种方法均可从多组分光谱数据矩阵重建出目标分子的光谱特征,重建效果略有差异。TFA能够克服干扰,提取出目标分子的光谱特征,其重建光谱与相应的参考光谱高度相似。BTEM方法无需目标分子的参考光谱,目标函数最优解所对应的谱图就是纯组分光谱。本研究利用两种方法各自的优势,用化学计量学方法定性分析OP/FT-IR光谱,不仅将BTEM方法应用于OP/FT-IR光谱,而且比较这两种方法的应用,为实现多组分OP/FT-IR光谱定性分析提供了新思路。     

优化迭代目标转换因子分析法

本文采有一系列步骤，如优化波长集合与优化标准浓度阵的选择，其目的是为了尽量发掘组份间的内在差异且在计算过程中予以保持，降低组份间相关性来改善迭代目标转换因子分析法的分辨混合体系的性能。应用该优化迭代目标转换因子分析法，对二元稀土和三元氨基酸体系进行光度法多组份同时测定，结果满意。     

Resolution prediction and optimization of temperature programme in comprehensive two-dimensional gas chromatography

A model is developed for predicting the resolution of interested component pair and calculating the optimum temperature programming condition in the comprehensive two-dimensional gas chromatography (GC x GC). Based on at least three isothermal runs, retention times and the peak widths at half-height on both dimensions are predicted for any kind of linear temperature-programmed run on the first dimension and isothermal runs on the second dimension. The calculation of the optimum temperature programming condition is based on the prediction of the resolution of "difficult-to-separate components" in a given mixture. The resolution of all the neighboring peaks on the first dimension is obtained by the predicted retention time and peak width on the first dimension, the resolution on the second dimension is calculated only for the adjacent components with un-enough resolution on the first dimension and eluted within a same modulation period on the second dimension. The optimum temperature programming condition is acquired when the resolutions of all components of interest by GC x GC separation meet the analytical requirement and the analysis time is the shortest. The validity of the model has been proven by using it to predict and optimize GC x GC temperature programming condition of an alkylpyridine mixture.     

Local resolution of two-way data from multicomponent equilibria

A self-modeling curve resolution (SMCR) method is proposed to calculate concentration and spectral profiles for the two-way spectral data from an equilibrium containing several chemical components. The proposed method has three main distinctive steps: (i) fixed size moving window evolving factor analysis (FSMWEFA) is used to identify the selective and zero concentration regions for a desired component, (ii) orthogonal projection resolution (OPR) is used to calculate its concentration profile and (iii) the component striping is done directly to resolve other components. The results of simulated and real polyprotic acid dissociation equilibria showed that the proposed combined method performs well even in situation when the successive stepwise equilibrium constants are close to each other. The applicability of method for resolving the triprotic acid system with rank deficiency due full spectral overlapping of two involved chemical species also is shown.     

A Computer Program for the Selection of Gradient Elution in High Performance Liquid Chromatography

Abstract

A computer program is presented for the selection of a gradient mobile phase that will give the same resolution for all the component pairs in the mixture. Each pair is treated as a separate experiment. The computer is used to compile these experiments and to recommend an optimum gradient.     

Identification of essential components of Houttuynia cordata by gas chromatography/mass spectrometry and the integrated chemometric approach

Starting with Biller-Biemann's work [J.E. Biller, K. Biemann, Anal. Lett. 7 (1974) 515], various kinds of approaches have been proposed to extract GC/MS data to obtain pure components responses. In this paper, an integrated chemometric approach is proposed, which combine four sequential steps, data pretreatment, component perception, resolution and component identification, and then the proposed approach is manipulated to analyze the essential oils of a herbal medicine named Houttuynia cordata (HC). On the basis of the selective information obtained from both chromatograms and mass spectra, the proposed integrated chemometric approach can resolve the two-way GC/MS responses matrix into pure chromatograms and mass spectra without any model assumption on the peak shape. The resolution results obtained from HC samples demonstrate the performance of the proposed approach and indicate that it may be a promising one for analyzing complex chromatograms.     

Two novel procedures for automatic resolution of two-way data from coupled chromatography

In order to deal with the problem of simultaneous qualitative and quantitative analysis of the complicated samples in analytical chemistry, two novel procedures for automatic resolution of two-way data from coupled chromatography were developed in this work. The first can be used to determine automatically the number of components involved in a certain peak cluster. The second method is an iterative resolution procedure named the stepwise key spectrum selection which has also been developed to resolve automatically the spectra and chromatographic profiles of every component in the peak cluster investigated. The results obtained from simulated and real data show that the proposed methods perform fairly well.     

Inner chromatogram projection (ICP) for resolution of GC-MS data with embedded chromatographic peaks

The chromatographic peak located inside another peak in the time direction is called an embedded or inner peak in contradistinction with the embedding peak, which is called an outer peak. The chemical components corresponding to inner and outer peaks are called inner and outer components, respectively. This special case of co-eluting chromatograms was investigated using chemometric approaches taking GC-MS as an example. A novel method, named inner chromatogram projection (ICP), for resolution of GC-MS data with embedded chromatographic peaks is derived. Orthogonal projection resolution is first utilized to obtain the chromatographic profile of the inner component. Projection of the two-way data matrix columnwise-normalized along the time direction to the normalized profile of the inner component found is subsequently performed to find the selective m/z points, if they exist, which represent the chromatogram of the outer component by itself. With the profiles obtained, the mass spectra can easily be found by means of a least-squares procedure. The results for both simulated data and real samples demonstrate that the proposed method is capable of achieving satisfactory resolution performance not affected by the shapes of chromatograms and the relative positions of the components involved.     

Increasing the mass resolution in a TOF aerosol mass spectrometer using a nonlinear post focusing method

The mass resolution for the time of flight aerosol mass spectrometer for aerosol component analysis is dependent on the initial direction and energy of the ions. We have found that the shape of the optimum post focusing electric field is nonlinear. The maximum electric potential should be applied to the ions whose initial direction is 90°. To determine the post focusing effects, a laser ablation mass spectrometer was installed. By using this LA-MS, it was found that the average energy distribution of the laser ablated ions was 8 eV. To establish an optimum mass resolution, a time delay and a high voltage are needed. The study results showed that 1500 ns and 3.7 kV, respectively, were the optimum parameters for time delay and voltage for this system. Using these optimized parameters, good resolution between the isotope mass signals of copper was achieved.     

Development and validation of an improved method for the analysis of vancomycin by liquid chromatography selectivity of reversed-phase columns towards vancomycin components

The current method prescribed in official monographs for the purity control of vancomycin is inappropriate in that several components are not separated from each other and other components are coeluted with the main component vancomycin B. The method uses an ODS column at pH 3.2. In this study, several changes were introduced in order to improve the separation. The optimization of the separation method at low pH indicated that pH 1.7 was optimum and that the use of dioxane as organic modifier drastically improved the separation. These conditions were used to test a set of more than 40 reversed-phase columns for their selectivity towards vancomycin components. The selection of the most suitable columns was performed by means of principal component analysis. Most of these columns did not allow the separation of didechlorovancomycin from monodechlorovancomycin 1. It was found that neutral to slightly alkaline mobile phases allowed better separation. Further optimization of the separation method and a robustness study were performed by means of experimental design. This optimization indicated that pH 7.7 was optimum and gradient elution was also used to effect complete analysis. The final method uses a Kromasil column and the mobile phase comprises dioxane, water and ammonium formate solution pH 7.7. The separation of monodechlorovancomycin 2 and of some unknown impurities from the main component vancomycin B is described for the first time. The method shows good repeatability, linearity and sensitivity.     

Optimization of the LC Separation of 15 Phenolic Compounds with Plackett–Burman Designs

In this study Plackett–Burman designs have been used to find the optimum conditions for separation of 15 phenolic compounds by LC. The responses used were the minimum resolution between two peaks and the analysis time. The adopted factors and experimental field were organic modifier (MeOH or ACN), percentage of acetic acid in the aqueous phase, flow rate, gradient with ten steps of percentage increase of the organic component of the mobile phase, and ten factors representing the duration of the steps. Use of Plackett–Burman designs achieved separation of the phenolic compounds within 45 min.