Time-series analysis in analytical process control

Analysis of time series tries to extract tendencies from measured values dependent on time. For this purpose the cusum technique has proved to be a very sensitive tool for the evaluation of both current and completed time series. Even very weak tendencies can be detected at a high level of noise. Time-series analysis further tries to predict values to come from hitherto performed measurements. As a very flexible model exponential smoothing could be successfully used. Even for processes with a high extent of non-stationarity this model allowed a good prediction owing to the dynamics of the process. Three types of time-series analysis, i.e., evaluation of current measurements, retrospective evaluation and prediction of data (also known as “in vivo”, “post mortem” and “in futurum” time-series analysis) are demonstrated for problems stemming from analytical process control.     

Application of wet chemistry techniques to process analysis and control

The availability of reliable and rugged automatic titrators, flow-injection analysers and ion chromatographs provides opportunities for their application in industrial process analysis. The control of industrial processes such as the removal of sulphur during gas treatment presents a challenge as accurate on-line and in-line analysers are required. The application of automatic titrators and ion chromatographs to the compositional analysis of caustic and alkanolamine gas sweetening solutions is described. Comparisons with other techniques such as flow-injection analysis and ultraviolet and near-infrared spectrometry are made and the pertinent features and benefits of each are discussed.     

Fuzzy theory in analytical chemistry

The concept of fuzzy theory is described in order to provide the analyst with the means for dealing with vague statements, uncertain observations or the fuzziness of human perception and interpretation, in general. In a theoretical part, basic notions of fuzzy theory are given, such as types of membership functions, operations with fuzzy sets, definitions of fuzzy numbers, points, functions, and relations, and the use of linguistic variables. The difference between fuzziness and probability is outlined. The applications section demonstrates advantages of fuzzy theory methods compared to common mathematical methods with respect to data handling for calibration of analytical methods, to classification of Chromatographie and spectroscopic patterns, to component identification and multicomponent analysis, and to designing fuzzy expert systems for selection of analytical procedures.     

The role of analytical chemistry in process quality control

The growing need for quality supervision and control in production processes is briefly outlined. After a summary of available process analytical devices, and a short discussion of their possibilities and limitations, an alternative approach is discussed. This approach is based on the development of a dynamic process model which allows on-line quality predictions to be made by means of so- called state estimators. The advantage is that it becomes possible to use quantities which give only indirect information about the product quality, but which are more readily accessible for continuous or on-line monitoring in earlier stages of the process.     

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.     

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。     

Green analytical chemistry as an integral part of sustainable education development

1. Download : Download high-res image (137KB)
2. Download : Download full-size image

     

Teaching the integrated and modern perspectives of analytical chemistry

The present situation of analytical chemistry teaching within a chemistry curriculum is exemplified by the reformed chemistry curriculum in Germany. This approach is contrasted with teaching analytical chemistry within a novel curriculum in natural sciences termed 'applied science'. The latter curriculum ensures a superior education in chemistry, physics, biology, mathematics and information science, thus gaining an integrated perspective of analytical chemistry.     

Teaching the integrated and modern perspectives of analytical chemistry

The present situation of analytical chemistry teaching within a chemistry curriculum is exemplified by the reformed chemistry curriculum in Germany. This approach is contrasted with teaching analytical chemistry within a novel curriculum in natural sciences termed ‘applied science’. The latter curriculum ensures a superior education in chemistry, physics, biology, mathematics and information science, thus gaining an integrated perspective of analytical chemistry.     

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。     

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。     

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.     

撰写教育教学论文是提升教学研究的好手段

简述了做好教学研究是提高教育教学质量的关键,撰写教育教学论文是提升教学研究的好手段。明确了撰写教育教学论文的目的和内容。以教学研究中撰写的论文示例强调了写好论文的基础来源于扎实的教学实践,功力来源于科学研究,做法来源于把教学研究当作科学研究那样去做。     

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.     

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.