Influence of transition metal doping on tris(thiourea)zinc(II) sulphate crystals

Optical, thermal and dielectric properties of Ni(II)-doped tris(thiourea)zinc(II) sulphate single crystals grown by slow evaporation solution growth technique has been investigated. The lattice parameters of the as-grown crystals were obtained by single crystal X-ray diffraction analysis. The modes of vibrations of different functional groups present were identified by FT-IR studies. The surface morphological changes are observed in the doped specimen. The structure and the crystallinity of the material were confirmed by powder X-ray diffraction analysis. The UV–vis optical absorption spectrum shows the lower optical cut-off at ∼284 nm and the crystals are transparent in the entire visible region. The relative second harmonic generation efficiency measurements reveal the enhancement of efficiency by doping with small quantities of Ni(II).     

A class of convolution integral equations involving a generalized polynomial set

The aim of this paper is to derive a solution of a certain class of convolution integral equation of Fredholm type whose kernel involves a generalized polynomial set. Our main result is believed to be general and unified in nature. A number of (known or new) results follow as special cases, simply by specializing the coefficients and parameters involved in the generalized polynomial set. For the sake of illustration, some special cases are mentioned briefly.     

Solubility diagrams of the potassium iodide-water-ethanol and iodine-water-ethanol ternary systems

The solubility of potassium iodide and iodine in water-methanol mixed solvents was studied by the method of sections at 25°C and atmospheric pressure. The solubility of potassium iodide was found to decrease as the content of ethanol in aqueous-alcoholic solutions increased. The solubility of crystalline iodine had a complex dependence on mixed solvent composition; it was maximum in mixtures containing 90 wt % alcohol. The compositions of the solid phases that crystallized in the KI-H₂O-C₂H₅OH and I₂-H₂O-C₂H₅OH systems were substantiated by X-ray measurements.     

State of Platinum Group Metals and Gold in Mineral Acid Solutions and the Catalytic Activity of These Metals in the Oxidation of N-Methyldiphenylamine-4-Sulfonic Acid

The state of rhodium, iridium, platinum, and gold in HCl, HClO₄, H₂SO₄, and HNO₃ solutions was studied by capillary electrophoresis. The electrophoresis was performed in an acidic phosphate buffer solution using an unmodified fused-silica capillary. It was found that the catalytic activity of the metals in the reaction of N-methyldiphenylamine-4-sulfonic acid oxidation with periodates in weakly acidic solutions depends on the analyte speciation. It was found that rhodium and iridium cations formed upon the treatment of a sample with concentrated perchloric acid catalyze the above reaction; this is favorable for the selective determination of these cations in the presence of platinum and gold.     

The influence of surfactants on the acid—base and redox properties of reagents of the diphenylamine series

The influence of aqueous solutions of surfactants on the redox and acid—base properties of diphenylamine redox reagents was studied by potentiometric titration and UV spectroscopy. The formal redox potentials, the pK _a values of the reagents in aqueous solutions and in the presence of surfactants, and the constants of binding of the reagents by micellar solutions of surfactants were estimated. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1386–1388, August. 2000.     

Application of MATLAB package for the automation of the chemometric processing of spectrometric signals in the analysis of complex mixtures

We describe three types of automatic software for the chemometric processing of spectrometric data. The software was developed in the MATLAB working environment and includes data import, mathematical preprocessing, chemometric analysis, and generation of a report file. The software is designed to solve problems regarding identification of some components of multicomponent mixtures, determination of compounds with overlapping signals, and differentiation of samples by their spectral responses. To test the software, we present examples of spectrometric analyses of coffee, fruit juices, and alcoholic beverages using chemometric methods of independent component analysis (ICA) and partial least squares–discriminant analysis (PLS–DA). In particular, we simulated electronic absorption spectra for the identification of three artificial colors (E110, E102, and E122) in alcoholic beverages, NMR spectra for the simultaneous determination of five components (acetic acid, γ-aminobutyric acid, arginine, acetaldehyde, and proline) in orange juice without using reference standards, and NMR spectra of coffee samples to determine its varietal authenticity (Arabica or Robusta). The duration of automatic chemometric processing did not exceed 1 min per sample. The developed software can be optimized for other matrices and/or brands of spectrometers.     

Independent component analysis (ICA) algorithms for improved spectral deconvolution of overlapped signals in 1H NMR analysis: application to foods and related products

The major challenge facing NMR spectroscopic mixture analysis is the overlapping of signals and the arising impossibility to easily recover the structures for identification of the individual components and to integrate separated signals for quantification. In this paper, various independent component analysis (ICA) algorithms [mutual information least dependent component analysis (MILCA); stochastic non‐negative ICA (SNICA); joint approximate diagonalization of eigenmatrices (JADE); and robust, accurate, direct ICA algorithm (RADICAL)] as well as deconvolution methods [simple‐to‐use‐interactive self‐modeling mixture analysis (SIMPLISMA) and multivariate curve resolution‐alternating least squares (MCR‐ALS)] are applied for simultaneous ¹H NMR spectroscopic determination of organic substances in complex mixtures. Among others, we studied constituents of the following matrices: honey, soft drinks, and liquids used in electronic cigarettes. Good quality spectral resolution of up to eight‐component mixtures was achieved (correlation coefficients between resolved and experimental spectra were not less than 0.90). In general, the relative errors in the recovered concentrations were below 12%. SIMPLISMA and MILCA algorithms were found to be preferable for NMR spectra deconvolution and showed similar performance. The proposed method was used for analysis of authentic samples. The resolved ICA concentrations match well with the results of reference gas chromatography–mass spectrometry as well as the MCR‐ALS algorithm used for comparison. ICA deconvolution considerably improves the application range of direct NMR spectroscopy for analysis of complex mixtures. Copyright © 2014 John Wiley & Sons, Ltd.