Evaluation of the Information Content of Solid-Sampling Spectrochemistry Methods Using the Theory of Information

The evaluation of analytical procedures is based on the determination of so-called primary “figures of merit” (metrological characteristics) of individual analytical elements (X) of the excitation procedures tested. Based on these experimental results, the information theory parameters, i.e., the information content and the related measures of information content, were depending on the relevance calculated. The final critical evaluation of the tested analytical procedures was realized by comparison of the given parameters.     

Modeling spreading-pressure-dependent binary gas coadsorption equilibria using gravimetric data

The present work proposes an approach to building nonideal coadsorption models in a thermodynamically consistent fashion, including the effects of pressure and spreading pressure, from simple gravimetric measurements. This is an "inverse problem" of parameter determination from appropriate and limited experimental data.The approach relies on the nonideal adsorbed solution theory, which includes activity coefficients and their dependence on spreading pressure, and on an original form of the excess Gibbs energy of mixing. A fully analytical development leads to explicit relations between the infinite dilution activity coefficients and three sets of independent information: the parameters of this excess Gibbs function, the limiting slopes of measured binary gravimetric curves at two different total pressures, and the properties of the single-component isotherms. From there, the four parameters of the model may be determined quasi-analytically and uniquely. The method is exemplified with the coadsorption of CO(2) and CH(4) on activated carbon, and a heterogeneous set of data. On one hand, the total adsorbed mass of the two components is measured at 1 bar by "incremental gravimetry." On the other hand, data obtained from independent batch-type equilibration measurements at 2 bar allow a comparison of calculated and measured data for the individual component concentrations. It is emphasized, however, that only total adsorbed mass data are needed for application of the method.     

Resolution enhancement of composite spectra using wavelet-based derivative spectrometry

An approach based on the using of the continuous wavelet transform (CWT) in derivative spectrometry (DS) is considered. Within the framework of the approach we develop a numerical differentiation algorithm with continuous wavelets for improving resolution of composite spectra. The wavelet-based derivative spectrometry (WDS) method results in best contrast in differential curves compared to the conventional derivative spectrometry method. A main advantage is that, as opposed to DS, WDS gives stable estimations of derivative in the wavelet domain without using the regularization. A wavelet shape and the information redundancy are of the greatest importance when the continuous wavelet transform is used. As an appropriate wavelet we offer to utilize the nth derivative of a component with a priori known shape. The energy distribution into scales allows one to determine a unique wavelet projection and in that way to avoid the information redundancy. A comparative study of WDS and DS with the statistical regularization method (SRM) is made; in particular, limits of applicability of these are given. Examples of the application of both DS and WDS for improving resolution of synthetic composite bands and real-world composite ones coming from molecular spectroscopy are given.     

Über die dilatometrisch indizierten Titrationen

The incorporation of alkali ions into the EDTA chelate system is followed by the dilatometric titration method. Evaluation of the titration curves permits, on one hand, the determination of the pK values for the individual complexes and, on the other hand, it allows the calculation of the volume of hydration sphere. Moreover, it can be shown that Li and Na ions, so long they are present in excess, form ion pairs with EDTA.     

Informationstheorie in der Analytik

Summary The information amount characterizing multicomponent analyses is derived for the qualitative and quantitative evaluation of independent and correlated analytical signals, respectively. It must be distinguished between detection and determination of certain selected components on the one hand and the identification of unknown components on the other hand. Selectivity, relevance and redundance of instrumental analytical methods are evaluated in connection with their potential information capacity. The information performance and effectivity are specified with regard to practical analytical problem solving.

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Teil I: Fresenius Z Anal Chem (1987) 327:312     

Determination of the ionic composition of perfluorinated sulfocationite membranes based on Donnan potential estimates

An express method for determination of the membrane ionic composition is developed based on the possibility of estimating the Donnan potential difference on the individual studied-solution/membrane interface. The Donnan potential is assessed using a new device one end of which serves as the ion-selective electrode sensor. The ionic composition of perfluorinated sulfocationite membranes is determined in systems with mixed inorganic electrolyte solutions by comparing the Donnan potentials in a given system and the reference system. As the reference, a system with perfluorinated sulfocationic membrane and individual potassium chloride solutions is used. The time of one measurement does not exceed 10–15 min. The accuracy and sensitivity of determination were 3% and 0.02 mmol/g, respectively.     

Contribution a l’etude de la determination de Be,B, C,N, O et F par activation Au moyen de p,d,3He et α

A set of curves and numerical values is given, representing the relative importance of the main nuclear interferences involved in the determination of Be, B, C, N, O and F by p, d,³He and α activation. The possibilities offered by these charged particles and γ photons are compared, taking into account detection sensitivities on the one hand and interferences on the other. It is then possible to define the optimum irradiation conditions for the standard determination of each of these light elements.     

High-performance liquid chromatographic determination of beta-adrenoceptor blocking agents in body fluids

Several reports have been published reviewing high-performance liquid chromatographic (HPLC) methods for the determination of beta-adrenoceptor blocking agents (beta-blockers) in biological materials (Flouvat et al., 1981; Mehta, 1983; Marko and Soltés, 1984; Ahnoff et al., 1985; Tkaczyková and Safarík, 1987). Of these, the paper by Mehta (1983) briefly summarizes the interrelationship between physiocochemical properties of beta-blockers with prechromatographic treatment of biological samples, as well as with the HPLC methods used for the determination of 12 beta-adrenoceptor blocking drugs. The work by Ahnoff et al. (1985) concerning the monitoring of cardiovascular drugs also deals with HPLC assays of 18 beta-blockers in plasma. The Appendix to this report presents the great majority of HPLC methods for determining 30 beta-blockers in various body fluids. HPLC methods providing resolution and determination of individual beta-blocker enantiomers have not been included since this topic is being covered by Walle and Walle (1989). The Appendix is just a guide to the methods reviewed for the HPLC determination of parent beta-blockers as well as some of their metabolites co-assayed in various body fluids. It does not include details such as the internal standard, recovery, setting of the detector, limit of determination, etc., given in the individual methods listed. The isolation technique of the drug(s) from the given body fluid represents the main step in the sample work-up procedure. Along with this information, only the type of the HPLC column packing and the detection principle used by each method's developers are given.     

KINMODEL (AGDC): a multipurpose computational method for kinetic treatment

KINMODEL (AGDC) is a kinetic computational methodology that is valid for the treatment of any reaction mechanism and that allows the determination of different kinetic and non-kinetic parameters from the experimental data acquired by monitoring absorbance at one or several different wavelengths. It is a numerical computational model that can be applied to any reaction mechanism, with the advantage that on changing the treatment from one mechanism to another it is not necessary to modify even a single line of the program code since it automatically establishes and solves the set of differential rate equations. It is able to treat a broad set of reaction mechanisms in the individual and joint determination of the following groups of parameters (a) the individual rate constants of the different reaction mechanisms; (b) the values of the molar absorption coefficients (which are very valuable in the case of intermediate species and their identification) of all the species involved in the mechanism, and (c) the concentrations of the species participating in the mechanism. The program can be used by non-experts in the field and it is able to treat mechanisms involving ambiguities in the solutions and in the identification of parameters when kinetic constants and molar absorption coefficients are optimized together, and it allows a discrimination to be made between the possible mechanisms responsible for the course of the reaction after the residuals have been analyzed statistically, automatically choosing the one that best fits the kinetic data.     

Thermodynamics of homogeneous equilibrium copolymerization from the point of view of the Flory-Huggins theory

A general treatment of the thermodynamics of binary copolymerization from the point of view of the Flory-Huggins theory is given. The relations allow one to determine, on the basis of experimental data, the thermodynamic parameters of copolymerization and the parameters of intercomponent interaction (χ). On the other hand, when these parameters are known, it is possible to predict, for any initial set of conditions, the equilibrium concentrations of comonomers and the equilibrium microstructure of a copolymer. The presented simulations indicate that positive values of interaction parameters increase the volume fractions of copolymer units in equilibrium with comonomers, in comparison to an analogous copolymerization system without intercomponent interactions.     

Röntgenkleinwinkelstreuung von Mehrphasensystemen Interpretation der Elektronendichtefluktuation

The mean square fluctuation of the electron density of a multi-phase system is determined by the electron densities and the volume fractions of the phases of the system. On the other hand the same quantity can be measured directly by means of small angle X-ray scattering (SAXS). For the interpretation of the measuring value obtained additional information is required. In the case of a two-phase-system the knowledge of the electron density difference between the two phases enables the determination of their volume fractions and vice versa. The knowledge of further parameters is necessary for the evaluation of a three-phase-system. It is shown that for the determination of the void fraction of a semi-crystalline high polymer the crystallinity of the sample must be taken into account, especially when the void fraction is small.     

Decision trees in selection of featured determined food quality

The determination of food quality, authenticity and the detection of adulterations are problems of increasing importance in food chemistry. Recently, chemometric classification techniques and pattern recognition analysis methods for wine and other alcoholic beverages have received great attention and have been largely used. Beer is a complex mixture of components: on one hand a volatile fraction, which is responsible for its aroma, and on the other hand, a non-volatile fraction or extract consisting of a great variety of substances with distinct characteristics. The aim of this study was to consider parameters which contribute to beer differentiation according to the quality grade. Chemical (e.g. pH, acidity, dry extract, alcohol content, CO(2) content) and sensory features (e.g. bitter taste, color) were determined in 70 beer samples and used as variables in decision tree techniques. This pattern recognition techniques applied to the dataset were able to extract information useful in obtaining a satisfactory classification of beer samples according to their quality grade. Feature selection procedures indicated which features are the most discriminating for classification.     

Experimental shift allowance in the deconvolution of SIMS depth profiles

We study the deconvolution of the secondary ion mass spectrometry (SIMS) depth profiles of silicon and gallium arsenide structures with doped thin layers. Special attention is paid to allowance for the instrumental shift of experimental SIMS depth profiles. This effect is taken into account by using Hofmann's mixing‐roughness‐information depth model to determine the depth resolution function. The ill‐posed inverse problem is solved in the Fourier space using the Tikhonov regularization method. The proposed deconvolution algorithm has been tested on various simulated and real structures. It is shown that the algorithm can improve the SIMS depth profiling relevancy and depth resolution. The implemented shift allowance method avoids significant systematic errors of determination of the near‐surface delta‐doped layer position. Copyright © 2013 John Wiley & Sons, Ltd.     

Molecular mechanisms of signalling specificity via phosphorelay pathways in Arabidopsis

Multistep phosphorelay (MSP) pathways mediate a wide spectrum of adaptive responses in plants, including hormonal and abiotic stress regulations. Recent genetic evidence suggests both partial redundancy and possible functional cross-talk on the one hand and a certain level of specificity on the other. Here, we discuss recent achievements improving our understanding of possible molecular mechanisms of specificity in MSP. We consider a certain evolutionary conservation of ancestral two-component signalling systems from bacteria in a process of molecular recognition that, as we have recently shown, could be applied also to a certain extent in the case of plant MSP. Furthermore, we discuss possible roles of kinase and phosphatase activities, kinetics of both these enzymatic reactions, and phosphorylation lifetime. We include also recent findings on the expression specificity of individual members of MSP pathways and, finally, based on our recent findings, we speculate about a possible role of magnesium in regulation of MSP pathways in plants. All these mechanisms could significantly influence specificity and signalling output of the MSP pathways.     

Chemometric methods in energy dispersive X-ray fluorescence

Chemometric methods like principal component regression (PCR) are an excellent tool for the determination of matrix parameters from scattered radiation. PCR is used for the determination of carbon, hydrogen and oxygen from water and oil-based samples. This information is used in combination with fundamental parameters to determine zink in liquid samples. The method allows an accurate prediction of element concentrations in strong varying matrices.