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Prague, Czech Republic

The extracts of a homeopathic Chamomilla vulgaris preparation and chamomile tea were analyzed by surfaceenhanced Raman scattering and surface-enhanced IR spectroscopies. The aqueous or methanolic extracts were deposited on nanostructured, electrochemically prepared Au surfaces. Only saccharose was identified reliably in homeopathic sample. The presence of other component is evident but they could not be identified. Source

Mercury is one of the most dangerous environmental pollutants. Its toxicity depends on the mercury species present. Sample storage, methods of extraction of Hg species and their derivatization for GC are described and discussed. Source

Extracts of hibiscus leaves were analyzed by depositing on Au or Ag surfaces and subsequent measurement of their surface-enhanced Raman and IR spectra. The spectra reflect different composition of the extracts depending on polarity of the solvents used. The Raman spectra show characteristic bands of plant pigments while the IR spectra correspond to compounds in the cuticular waxy layer. The spectra obtained on Au and Ag surfaces show the bands of the same species while the spectral backgrounds are different. The adsorption/desorption cycles were also studied. The principal component analysis shows that the extracted compounds are mostly bonded by physisorption. Source

Determination of iron by the title method is complicated by spectral interferences of polyatomic ions, in particular ArO+ and CaO+. This work was focused on the possibility of reducing the interference using a dynamic reaction cell (DRC). The cell was pressurized with He (collision gas) and methane (reaction gas). Settings of DRC were optimized to achieve maximal efficiency of elimination of interferences. The determination of 56Fe and 57Fe was tested and the limit of detection and linearity of calibration curves were determined. The accuracy of the method was verified by analysis of a certified reference material. Source

Tatarkovica M.,Ustav analyticke chemie | Broncovaa G.,Ustav analyticke chemie | Krondakb M.,Ustav Jaderneho Vyzkumu Rez A.s.
Chemicke Listy | Year: 2012

A brief introduction to the theory of electrochemical impedance spectroscopy (EIS) and its application in chemical analysis using a system of metal electrodes with chemically or electrochemically deposited a sensitive layers. Galvanostatic EIS provides an electrode response to AC perturbation as a function of AC frequency. A constant DC together with superimposed AC is applied to the electrode. The measured quantity is the AC component of the voltage induced by the applied current. A Pt electrode coated with electrochemically generated polythiophene was used for measurement of impedance spectra. Galvanostatic EIS was applied in both quantitative and qualitative chemical analysis of model samples containing inorganic ions. Different methods of impedance spectra analysis were used and compared. In quantitative evaluation of impedance spectra, three methods (local minimum shift, impedance at constant AC frequency and phase shift of local minimum) were tested. The most suitable evaluation method was the first mentioned one. The simultaneous qualitative and quantitative analyses can be monitored using the principal component analysis. The method confirmed the recognition of ions with polythiophene electrode only. Source

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