Information theory in analytical chemistry

Summary The information of distribution analyses considerably exceeds that of integral analyses because of the spatial resolution. Distribution-analytical procedures are characterized by the ideal information amount which is determined by the ideal spatial resolving power A* that is theoretically attainable by actual scanning or mapping. Compared with it, the real information amount of distribution-analytical results are determined by a practical spatial resolving power and therefore, among others, by the number of measuring points. In dependence on the stochastical properties of multi-phase materials an optimum area can be specified for distribution-analytical investigations with a maximum information content. Methods of testing homogeneity can be characterized by means of the information theory in dependence on the arrangement of measuring points, on the evaluation of concentration or measuring values, and on their univariate, multiple or multivariate character.Part II: see [5]     

Factor analytical approaches for evaluating groundwater trace element chemistry data

The multivariate statistical techniques principal component analysis (PCA), Q-mode factor analysis (QFA), and correspondence analysis (CA) were applied to a dataset containing trace element concentrations in groundwater samples collected from a number of wells located downgradient from the potential nuclear waste repository at Yucca Mountain, Nevada. PCA results reflect the similarities in the concentrations of trace elements in the water samples resulting from different geochemical processes. QFA results reflect similarities in the trace element compositions, whereas CA reflects similarities in the trace elements that are dominant in the waters relative to all other groundwater samples included in the dataset. These differences are mainly due to the ways in which data are preprocessed by each of the three methods.

The highly concentrated, and thus possibly more mature (i.e. older), groundwaters are separated from the more dilute waters using principal component 1 (PC 1). PC 2, as well as dimension 1 of the CA results, describe differences in the trace element chemistry of the groundwaters resulting from the different aquifer materials through which they have flowed. Groundwaters thought to be representative of those flowing through an aquifer composed dominantly of volcanic rocks are characterized by elevated concentrations of Li, Be, Ge, Rb, Cs, and Ba, whereas those associated with an aquifer dominated by carbonate rocks exhibit greater concentrations of Ti, Ni, Sr, Rh, and Bi. PC 3, and to a lesser extent dimension 2 of the CA results, show a strong monotonic relationship with the percentage of As(III) in the groundwater suggesting that these multivariate statistical results reflect, in a qualitative sense, the oxidizing/reducing conditions within the groundwater. Groundwaters that are relatively more reducing exhibit greater concentrations of Mn, Cs, Co, Ba, Rb, and Be, and those that are more oxidizing are characterized by greater concentrations of V, Cr, Ga, As, W, and U.     

The stopped-flow technique in analytical chemistry

A critical survey of the stopped-flow technique is presented. The instrumentation typically used and the scope of its analytical applications are discussed. The stare-of-the-art of this technique and its wide possibilities in routine analyses are also considered.     

Independent component analysis and its applications in signal processing for analytical chemistry

Independent component analysis (ICA) is a statistical method the goal of which is to find a linear representation of non-Gaussian data so that the components are statistically independent, or as independent as possible. In an ICA procedure, the estimated independent components (ICs) are identical to or highly correlated to the spectral profiles of the chemical components in mixtures under certain circumstances, so the latent variables obtained are chemically interpretable and useful for qualitative analysis of mixtures without prior information about the sources or reference materials, and the calculated demixing matrix is useful for simultaneous determination of polycomponents in mixtures. We review commonly used ICA algorithms and recent ICA applications in signal processing for qualitative and quantitative analysis. Furthermore, we also review the preprocessing method for ICA applications and the robustness of different ICA algorithms, and we give the empirical criterion for selection of ICA algorithms in signal processing for analytical chemistry.     

Ionic liquids in analytical chemistry

Ionic liquids (ILs) are composed entirely of ions and they possess fascinating properties, including low volatility, tunable viscosity and miscibility, and electrolytic conductivity, which make ILs unique and useful for many applications in chemical analysis. The dramatic increase in the number of publications on ILs is indicative of the tremendous interest in this field from analytical chemists. This review summarizes recent efforts in the major subdisciplines of analytical chemistry, including extractions, gas chromatography, liquid chromatography, capillary electrophoresis, mass spectrometry, electrochemistry, sensors, and spectroscopy.     

Topological data analysis: A promising big data exploration tool in biology,analytical chemistry and physical chemistry

An important feature of experimental science is that data of various kinds is being produced at an unprecedented rate. This is mainly due to the development of new instrumental concepts and experimental methodologies. It is also clear that the nature of acquired data is significantly different. Indeed in every areas of science, data take the form of always bigger tables, where all but a few of the columns (i.e. variables) turn out to be irrelevant to the questions of interest, and further that we do not necessary know which coordinates are the interesting ones. Big data in our lab of biology, analytical chemistry or physical chemistry is a future that might be closer than any of us suppose. It is in this sense that new tools have to be developed in order to explore and valorize such data sets. Topological data analysis (TDA) is one of these. It was developed recently by topologists who discovered that topological concept could be useful for data analysis. The main objective of this paper is to answer the question why topology is well suited for the analysis of big data set in many areas and even more efficient than conventional data analysis methods. Raman analysis of single bacteria should be providing a good opportunity to demonstrate the potential of TDA for the exploration of various spectroscopic data sets considering different experimental conditions (with high noise level, with/without spectral preprocessing, with wavelength shift, with different spectral resolution, with missing data).     

轮胎橡胶多组分分析方法的研究

轮胎橡胶物证是涉车案件中常见物证,对于相关案件的侦破具有重要的物证价值。本文根据轮胎橡胶组分体系的特点,设计了以大型仪器为主线的多组分分析方案。所选用的仪器设备及方法有:裂解气相色谱仪(Py-GC)、裂解气相色谱与质谱联用仪(Py-GCMS)、差示扫描量热仪(DSC)、热重分析仪(TGA)、原子吸收分光光度计(AAS)、化学法;实验中,测试了轮胎橡胶的胶型、配合剂定性(防老剂定性、促进剂定性、其他助剂定性)、玻璃化温度,焓值,高聚物含量、配合剂含量、炭黑含量、无机填料(盐酸不溶物、氧化锌含量、二氧化硅含量)、硫含量等十三个测试项目;并将已知配方的硫化胶理论值与测试样品结果比对分析。分析结果表明:建立的系列方法的测试结果准确、可靠,可以为轮胎橡胶的分析鉴别提供技术支持。     

Sample screening systems in analytical chemistry

The state of the art and the potential of sample screening systems (SSS) for the expeditious, reliable selection of samples to meet the requirements of customers and legislation is presented and discussed. The underlying procedures use simple equipment and operations and provide a yes/no binary response that occasionally requires confirmation. After a brief discussion of the distinction between ‘screening' and ‘analysis' and the principal features of analytical screening systems, the main aims and features of SSS are presented. Several classifications of these allow one to offer a general view of the topic. Representative examples are classified according to the complexity of the sample pretreatment required, and are used to demonstrate the impact SSS may have on analytical chemistry in the next century.     

Teaching of process analytical chemistry

In the teaching of analytical chemistry for chemical engineering students it is essential today to teach the chemical analysis of dynamic systems, not only in the process control of the modern technological systems, where the control of composition or structure of different material streams is necessary, but also in all other instances where analysis, decision and intervention follow each other, forming a closed cycle. Teaching can be made effective if students already have a knowledge of the basic disciplines (including analytical chemistry). The schedule of the teaching programme should include the mathematical statistical treatment of process signals, quality of the signals, signal-improvement methods, characteristics of instruments, calibration and an introduction to sensors, analysers suitable for continuous or periodical measurements and local area networks. As practical exercizes an apparatus for investigation of the dynamic properties of a thermoanalytical detector system, a computer program for simulating process variables and the control loop including the measuring system are presented.     

分析化学信号在多尺度空间的滤噪

从多分辨率分析出发，结合离散正交小波变换(DWT)的理论，通过对各尺度下未抽取前的小波系数进行非线性滤波处理，达到在保护信号边缘的同时，有效实现白噪声及脉冲噪声的滤除。实验数据仿真结果研究也证明了该方法的可行性。     

光子晶体在分析化学中的应用

光子晶体是一新兴的光学材料,正越来越多地应用于分析化学领域,有可能成为新的研究热点。本文着重介绍与分析化学相关的光子晶体研究,特别关注其在色谱、毛细管与芯片电泳等分离分析方面的应用。     

Effluent analysis in analytical chemistry: an overview

This review summarizes and discusses effluent analysis, focusing on the methods and techniques that have been most frequently described in the literature since 1975. The methods are classified into four main categories: (1) physical and chemical properties; (2) inorganic metals analysis; (3) inorganic non-metallic analysis; (4) organic analysis.     

Ultrasound in analytical chemistry

Ultrasound is a type of energy which can help analytical chemists in almost all their laboratory tasks, from cleaning to detection. A generic view of the different steps which can be assisted by ultrasound is given here. These steps include preliminary operations usually not considered in most analytical methods (e.g. cleaning, degassing, and atomization), sample preparation being the main area of application. In sample preparation ultrasound is used to assist solid-sample treatment (e.g. digestion, leaching, slurry formation) and liquid-sample preparation (e.g. liquid–liquid extraction, emulsification, homogenization) or to promote heterogeneous sample treatment (e.g. filtration, aggregation, dissolution of solids, crystallization, precipitation, defoaming, degassing). Detection techniques based on use of ultrasonic radiation, the principles on which they are based, responses, and the quantities measured are also discussed.     

无机硫氧化合物的分析化学

介绍滴定分析和仪器分析对无机硫氧化合物水溶液的定量分离分析。滴定分析一般只能定量S^2-,S^2-2,SO^2-3,S2O^2-4,S2O^2-3,SxO^2-6等离子中的一种或多种的总量,仪器分析则对多种离子混合物的分离和定量非常有效。     

光谱结合主成分分析和模糊聚类方法的样品聚类与识别

针对紫外光谱结合化学计量学方法快速测定渣油烃族组成模型适应性问题,对渣油光谱进行主成分分析,以主成分得分作为聚类的特征变量进行模糊聚类,建立了光谱结合主成分分析和模糊聚类方法的样品聚类与识别方法和识别,为光谱结合化学计量分析方法中构正模型的正确选择提供了依据。     

Fourier methods in analytical chemistry

Summary Starting with the basic physical principles, the method of Fourier transform spectroscopy is described and explained. In addition to the technical and mathematical details, as for instance error correction, examples are presented with spectra obtained by this method. Advantages and disadvantages are discussed. New special developments in Fourier spectroscopy are briefly mentioned, e.g., phase modulation, compensative mode, and amplitude spectroscopy. Finally, some problems in analytical chemistry which have been studied by means of Fourier transform spectroscopy are summarized (155 references).

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Fourier-Methoden in der analytischen ChemieI. IR-Fourier-Transform-Spektroskopie

Zusammenfassung Ausgehend von den physikalischen Grundlagen wird das Verfahren der Fourier-Transform-Spektroskopie beschrieben und erläutert. Neben technischen und mathematischen Einzelheiten (wie z. B. Fehlerkorrektur) werden auch praktische Beispiele diskutiert. Vor- und Nachteile des Verfahrens werden erörtert. Neue, spezielle Entwicklungen in der Fourier-Spektroskopie werden kurz erwähnt, z. B. Phasenmodulation, Kompensationsmethode und Amplitudenspektroskopie. Abschließend werden einige analytische Probleme besprochen, die mit Hilfe der Fourier-Transform-Spektroskopie untersucht wurden (155 Literaturzitate).

     

Phase-transfer catalysis in analytical chemistry

Phase-transfer catalysis (PTC) has been a well-established technique on the synthesis of organic chemicals for more than three decades. Its scope and underlying mechanistic features have been the subject of numerous studies and appear to be recognized and understood.

This review is intended to approach the subject by focusing on the extraction–preconcentration–derivatization/reaction prior to analysis and to chronicle recent progress made. We present the salient aspects of PTC modes followed by a brief review of mechanistic considerations including reaction mechanisms, selectivity, rates and kinetics pointing out to the potency of PTC in analytical chemistry. Specific guidelines are given on how to optimize a PTC-based analysis with respect to catalyst, solvent, reaction conditions and more, based on reaction characteristics.

Finally, using the PTC principles as a framework, selected real-life applications are provided, the capabilities and limitations of PTC are addressed for the purpose of direct analysis of organic analytes and certain advantages are highlighted.     

Ferrocene-based derivatization in analytical chemistry

Ferrocene-based derivatization has raised considerable interest in many fields of analytical chemistry. This is due to the well-established chemistry of ferrocenes, which allows rapid and easy access to a large number of reagents and derivatives. Furthermore, the electrochemical properties of ferrocenes are attractive with respect to their detection. This paper summarizes the available reagents, the reaction conditions and the different approaches for detection. While electrochemical detection is still most widely used to detect ferrocene derivatives, e.g., in the field of DNA analysis, the emerging combination of analytical separation methods with electrochemistry, mass spectrometry and atomic spectroscopy allows ferrocenes to be applied more universally and in novel applications where strongly improved selectivity and limits of detection are required.     

Literature documentation in analytical chemistry

Zusammenfassung 67 Referate aus den Jahren 1978 und 1979 von 23 Originalarbeiten in verschiedenen Zeitschriften aus dem Jahr 1978 wurden aus den Anal. Abstr., Chem. Abstr. und Fresenius Z. Anal. Chem. als Stichproben ausgewählt und auf Informationsgehalt sowie Aufbau untersucht. Ein generell angewendetes Aufbauprinzip konnte in keiner der drei Zeitschriften festgestellt werden. Die Angaben analytisch-relevanter Ergebnisse erwiesen sich als unzureichend. Die Zusammenhänge zwischen Zusammenfassung in einer Originalarbeit und Referat werden aufgezeigt und diskutiert.

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Literature documentation in analytical chemistryII. Information content and structure of abstracts

Summary 67 Abstracts from 1978 and 1979 of 23 original papers in different journals from 1978 were selected as random samples from Anal. Abstr., Chem. Abstr. and Fresenius Z. Anal. Chem. for examination of information content and structure. A generally applied principle of structure for abstracts could not be recognized in any of these journals. The statements on analytically relevant results proved to be insufficient. The relationships between a summary in a original paper and the abstract were shown and discussed.

Teil I: Fresenius Z. Anal. Chem. 301, 359 (1980)