主成分分析同时单点pH滴定法研究

本文将主成分分析用于多组分同时单点ｐＨ滴定法中,讨论了方法原理,指定ｐＨ值的选择,建立了主成分分析常数矩阵,对四组分醇酮氧化酸试样及模拟样进行了多次测定,均获得了满意结果。     

Use of Chemometrics: Principal Component Analysis (PCA) and Principal Component Regression (PCR) for the Authentication of Orange Juice

ABSTRACT

Principal Component Analysis (PCA) was applied to a set of physico-chemical variables obtained from 41 samples of summer orange juice, in order to reduce the number of variables. Working with the covariance matrix, three components (which explained 98.27% of the variance) were taken. With the correlation matrix, four components which explained: 85.65% of the variance were taken. With the scores corresponding to both matrixes a principal component regression (PCR) was carried out against the dependent variable of Brix grades, so as to obtain two statistical models that would allow the detection of adulterations in pure orange juice, based on dilution and later masking by the addition of sugar. The models were tested with simulated dilutions of 41 samples of juice, to assess the effectiveness of each for the detection of adulterations. Both models turned out to be equally effective, detecting adulterations starting from about 15 % of dilution.     

Effect of Cysteic Acid Position on the Negative Ion Fragmentation of Proteolytic Derived Peptides

A study on the effect of cysteic acid position on the types of fragment ions formed by collision-induced dissociation (CID) of [M – H]⁻ ions is presented. Of particular note is the observation of d-type fragment ions for peptides that contain an N-terminal cysteic acid (fixed negative charge) and cleavable amino acid side chains possessing a β-γ carbon–carbon bond. For example, the CID mass spectrum of oxidized cys-kemptide (C_oxLRRASLG) [M – H + O₃]⁻ ions contains abundant series of d-type fragment ions, and similar results are observed for oxidized cysteine-containing ribonuclease A proteolytic peptides. The d _i fragment ions are assumed to arise by a charge-remote and/or charge-assisted fragmentation mechanism, which both occur at high collision energies and involve consecutive reactions (i.e., the formation of a _i ions followed by the elimination of the side chain to form d _i ions).     

支持向量机结台主成分分析辅助激光诱导击穿光谱技术识别鲜肉品种

为提高激光诱导击穿光谱技术(Laser-induced breakdown spectroscopy,LIBS)对鲜肉品种的识别率,采用支持向量机结合主成分分析算法辅助LIBS技术对鲜肉品种进行识别.对鲜肉切片用载玻片压平,采用LIBS技术对鲜肉组织(猪肉、牛肉和鸡肉)表面进行光谱数据的采集,每种鲜肉采集150幅光谱并进行随机排列,取前75幅光谱作为训练集建立模型,后75幅作为测试集测试建模结果.研究选取K、Ca、Na、Mg、Al、H、O等元素的49条归一化谱线数据进行主成分分析,并用所得数据建立支持向量机分类模型.结果表明,通过主成分分析降维,输入变量从49个优化减少到18个,模型建模速度从88.91 s降至55.52 s,提高了支持向量机的建模效率;并使预测集的平均识别率提高到89.11%.本研究为激光诱导击穿光谱技术在鲜肉品种快速分类领域提供了方法和数据参考.     

主成分分析同时单点R滴定法研究

将主成分分析用于单点Ｒ滴定法中，同时测定了镍矿中Ｎｉ，Ｃｕ，Ｃｏ含量，讨论了方法原理，指定电位的选择，建立了主成分分析常数矩阵，对２０个模拟样和矿样进行了分析，均获得满意结果。     

甲基氯硅烷初产品的组成分析

以气相色谱和色谱-质谱联用技术分析了甲基氯硅烷初产品的组成,对于其中的2-甲基-2-丁烯与甲基二氯硅烷的色谱重叠峰,采用醇解反应处理,并以样品中不会醇解的四甲基硅烷做参照来计算其含量。     

Thermal Decomposition of Medicinal Plant Raw Materials Based on Principal Component Analysis

Studies on the thermal decomposition of commercial raw plant materials used in medicine were performed. 144 independent samples of plant materials — herbs, leaves,flowers, inflorescences, fruits, roots, rhizomes and barks, collected by Medicinal Plant Works‘Herbapol’, were analyzed. Thermal decomposition was performed using OD-103 Derivatograph. As a result of analysis, it was established, that thermal decomposition of majority of samples proceeds through three stages. The analysis of fruits revealed, that their thermal decomposition proceeds in four stages. In order to obtain a more clear classification of the analyzed plant materials principal component analysis (PCA) was applied. Interpretation of the PCA results allows to state, that samples of raw materials from the same plant species in majority of cases are characterized by similar course of thermal decomposition due to similar chemical composition. In this way the differences in general chemical composition of medicinal plants raw materials can be determined. This revised version was published online in August 2006 with corrections to the Cover Date.     

ToF-SIMS Depth Profiling of Trehalose: The Effect of Analysis Beam Dose on the Quality of Depth Profiles

In static secondary ion mass spectrometry (SIMS) experiments, an analysis dose of 10(12) ions/cm(2) typically produces optimum results. However, the same dose used in dual beam depth profiling can significantly degrade the signal. This is because during each analysis cycle a high-energy beam is rastered across the same x-y location on the sample. If a sufficient amount of sample is not removed during each sputter cycle, the subsequent analysis cycle will sample a volume degraded by the previous analysis cycles. The dimensionless parameter R' is used to relate the amount of damage accumulated in the sample to the amount of analysis beam dose used relative to the etching beam. Depth profiles from trehalose films spin-cast onto silicon wafers acquired using Bi(1) (+) and Bi(3) (+) analysis beams were compared. As R' increased, the depth profile and the depth resolution (interface width) both degraded. At R' values below 0.04 for both Bi(1) (+) and Bi(3) (+), the shape of the profile as well as the depth resolution (9 nm) indicated that dual beam analysis can be superior to C(60) single beam depth profiling.     

主成分-线性判别法对大气易挥发性有机化合物的预警

应用遥感傅里叶变换红外光谱,采用主成分提取-线性判别分析(PCA-LDA)技术,对丙酮、二氯甲烷、甲苯、苯、氯仿和甲醇等六组分的任意混合体系进行定性鉴别。被选用的这6种大气有毒有机化合物的红外光谱图相互间存在着严重的混叠,并和反向传播人工神经网络(BP-ANN)的预测结果进行了比较。PCA-LDA的鉴别判对率达92.2%,识别率94.4%,误判率7.8%;BP-ANN分别为91.1%、95.6%和8.9%。结果表明PCA处理克服了LDA对多变量数据预测的局限性,预测性能和BP-ANN相当。鉴于BP-ANN计算耗时和繁琐,PCA-LDA模型被确定为建立VOCs预警模型最适当的方法。     

CO Adsorption on N2‐Precovered NaY Faujasite: A FTIR Analysis of the Resulting Adsorbed Species

To productively complete the information regarding the reversible adsorption of a gas mixture on the micropores of cationic zeolites, the adsorption of the two gases N₂ and CO on NaY faujasite is taken as a model case study. We analyze herein CO adsorption (77 K) on two distinct N₂‐precovered NaY sets (low and medium). We outline the continuous desorption of N₂ adducts during CO admittance to full N₂ desorption for the highest CO loadings. These features contrast with preceding results obtained for N₂ loading on CO‐precovered NaY. By comparing these results with the sole CO admission and combining both studies regarding the co‐adsorption sets, we demonstrate the influence of the basic strength of the two gases regarding the nature of the surface‐adsorbed species formed. We also propose and discuss a hypothesis regarding the formation of adsorbed mixed species having both N₂ and CO as ligands. These new findings strengthen the statistical response of IR signatures as a helpful proposal for analyzing adsorbed species and their assignments. This survey completes the molecular understanding of gas‐mixture adsorption that lacks experimental data to date.     

SEM-EDS investigation on PM10 data collected in Central Italy: Principal Component Analysis and Hierarchical Cluster Analysis

Background

Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) were applied on PM10 particle data in order to: identify particle clusters that can be differentiated on the bases of their chemical composition and morphology, investigate the relationship among the chemical and morphological parameters and evaluate differences among the sampling sites. PM10 was collected in 3 different sites in central Italy characterized by different conditions: yard, urban and rural sites. The concentration of 20 chemical parameters (C, O, Na, Mg, Al, Si, P, Cd, Cl, K, Ca, Sn, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn) were determined by Scanning Electron Microscopy – Energy Dispersive X-ray Spectroscopy (SEM-EDS) and the particle images were processed by an image analysis software in order to measure: Area, Aspect Ratio, Roundness, Fractal Dimension, Box Width, Box Height and Perimeter.

Result

Results revealed the presence of different clusters of particles, differentiated on the bases of chemical composition and morphological parameters (aluminosilicates, calcium particles, biological particles, soot, cenosphere, sodium chloride, sulphates, metallic particles, iron spherical particles). Aluminosilicates and Calcium particles of rural and urban sites showed a similar nature due to a mainly natural origin, while those of the yard site showed a more heterogeneous composition mainly related to human activity. Biological particles and soot can be differentiated on the bases of the higher loads of Fractal Dimension, which characterizes soot, and content of Na, Mg, Ca, Cl and K which characterize the biological ones. The soot of the urban site showed higher loadings of Roundness and Fractal Dimension than the soot belonging to the yard and rural sites, this was due to the different life time of the particles. The metal particles, characterized mainly by the higher loading of iron, were present in two morphological forms: spherical and angular particles. The first were generated by a fusion process at high temperature, while the second one had crustal origin (those characterized by typical terrigenous elements) and also human origin.

Conclusion

In this work a protocol for the morphological-chemical characterization of single particles has been developed. SEM analysis allows to classify particles in 10 different families and PCA and HCA have provided information about the sources of PM and similarities and differences among the sites.

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主成分分析用于浙贝母中无机元素含量的研究

采用原子吸收光谱（AAS）法测定了10个浙贝母样品中12种无机元素的含量,建立浙贝母无机元素指纹图谱,并用SPSS13．0方差分析和主成分分析对浙贝母中的微量元素进行了分析。结果表明,浙贝母的特征无机元素是Cd,Cu,Pb,Mg,Cr,Fe,Zn。可见主成分分析法是浙贝母无机元素分析的有效方法。     

Use of Principal Component and Cluster Analysis for the Comparison of Reversed-Phase HPLC Columns

Abstract

The retention of ethoxylated nonylhylphenyl surfactants was determined in reversed-phase high-performance liquid chromatography (RP-HPLC) using various supports (C1, C2, C6, C8, C18, polyethylene-coated silica, and polyethylene-coated alumina). The retention data matrix was evaluated both by principal component analysis and cluster analysis. The retention characteristics of both polyethylene-coated supports were similar to that of C1, the retention capacity of RP columns for surfactants increased with the increasing length of the covalently bonded hydrocarbon chain. The retention of ethoxylated surfactants depended nonlinearly on the length of ehtyleneoxide chain suggesting that the polar ethyleneoxide chains are in folded state under the chromatographic separation.     

非那西丁的合成与复方阿司匹林的主成分分析——推荐一个有机化学实验

以对氨基苯乙醚为原料,与乙酸成盐提高溶解度与反应活性,再与乙酸酐发生亲核取代反应,两步制备非那西丁.以核磁共振氢谱对化合物结构进行解析,并且利用薄层色谱和高效液相色谱对复方阿司匹林中的有效成分进行分析,讨论了色谱技术之间的区别与联系.本实验内容包括加热回流、离心、重结晶、核磁共振波谱以及薄层色谱和高效液相色谱的应用,有利于培养学生的综合分析问题能力.     

Spectroscopic Investigation of the Structure of a Protein Adsorbed on a Hydrophobic Latex

Spectroscopic methods provide a powerful tool for investigating the structural properties of immobilized proteins. For that purpose, there was a strong need for a hydrophobic particle that allows determination of the adsorbed protein conformation by fluorescence and circular dichroism. Among the various hydrophobic suspensions that are available, perfluoro-alkoxy fluoro carbon Teflon latex satisfies the requirements of low light absorption and scattering. As an example, preliminary results of structural changes of a proteolytic enzyme dissolved in aqueous solution and in the adsorbed state are given.     

Classification of Wines Based on Combination of ^1H NMR Spectroscopy and Principal Component Analysis

A combination of ^1H nuclear magnetic resonance （NMR） spectroscopy and principal component analysis （PCA） has shown the potential for being a useful method for classification of type, production origin or geographic origin of wines. In this preliminary study, twenty-one bottled wines were classified/separated for their location of production in Shacheng, Changli and Yantai, and the types of the blended, medium dry, dry white and dry red wines, using the NMR-PCA method. The wines were produced by three subsidiary companies of an enterprise according to the same national standard. The separation was believed to be mainly due to the fermentation process for different wines and environmental variations, such as local climate, soil, underground water, sunlight and rainfall. The major chemicals associated with the separation were identified.     

Two‐Dimensional Infrared Correlation Spectroscopy and Principal Component Analysis on the Carbonation of Sterically Hindered Alkanolamines

Despite the academic and industrial importance of the chemical reaction between carbon dioxide (CO₂) and alkanolamine, the delicate and precise monitoring of the reaction dynamics by conventional one‐dimensional (1D) spectroscopy is still challenging, due to the overlapped bands and the restricted static information. Herein, we report two‐dimensional infrared correlation spectroscopy (2D IR COS) and principal component analysis (PCA) on the reaction dynamics of a sterically hindered amine, 2‐[(1,1‐dimethylethyl)amino]ethanol (TBAE) and CO₂. The formation of carbonate rather than carbamate species, which contribute to the unusual high working capacity of ～1 mole CO₂ per mole of TBAE at 40 °C, occurs through deprotonation of the hydroxyl group, protonation on the nitrogen atom of the amino group, and formation of a carbonate species due to the steric hindrance of the tert‐butyl group. In particular, PCA captures the chemical transition into a carbonate species and the main contributions of ${\nu _{{\rm{CO}}_2 } }$ , ${\nu _{{\rm{OH}}} }$ , ${\nu _{{\rm{C - N}}} }$ , and ${\nu _{{\rm{C}} = {\rm{O}}} }$ bands to the carbonation, while 2D IR COS verifies the interrelation of four bands and their changes. Therefore, these results provide a powerful analytic method to understand the complex and abnormal reaction dynamics as well as the rational design strategy for the CO₂ absorbents.     

Chromic Acid Adsorbed on Kieselguhr: A New Reagent for the Oxidation of Primary Alcohols to Aldehydes

A new reagent, chromic acid adsorbed on kieselguhr, suitable for the oxidation of primary alcohols to the corresponding aldehydes is described.     

Study on Light Aging of Silk Fabric by Fourier Transform Infrared Spectroscopy and Principal Component Analysis

To investigate environmental effect on cultural materials, Fourier transform infrared technique (FTIR/ATR) was applied to analyze the silk aging process. Changes in chemical and conformational structures of silk fabric undergoing ultraviolet induced degradation were investigated. The IR spectra provided strong bands of photosensitive amide I, II, and III. For overlapping amide III region, both of the original and second-derivative IR spectra revealed that UV irradiation induced the structural transformation from β-sheet domain to β-turn conformation, which was supported by the increase of β-turn marker band at 1015 cm^?1 associated with polyglycine. Additionally the reduced bands associated with (GlyAla)_n segment at 1000 and 976 cm^?1, and the decreased band at 1070 cm^?1 related to β-sheet structure also illustrated the conformational transition. Furthermore, we applied a chemometric method of principal component analysis for the evaluation of silk degradation based on variations in amide I spectral region. The score plot using the first two principal components effectively summarized the general trend of silk-aging and revealed the quick degradation appeared in the initial stages (12 h and 24 h) and the 108-hr stage. This work provides a potential novel application of the infrared spectroscopy in noninvasive qualitative and quantitative investigation of silk degradation.