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Abstract  

The application of differential scanning calorimetry (DSC) for purity determination is well documented in literature and is used amongst others in the analysis of pure organic crystalline compounds. The aim of this work is to examine whether the DSC method for purity determination consistently produces values for the purity of polycyclic aromatic hydrocarbons (PAHs) which are sufficiently accurate as required for the certification of reference materials. For this purpose, 34 different existing PAH certified reference materials were tested. The DSC results are shown to be consistent with the results obtained by other methods assessing the organic impurities content in PAHs, like gas chromatography (GC), high performance liquid chromatography (HPLC) and mass spectrometry. Significant differences between the measured values and the certified purity values were observed only in a limited number of cases.

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Abstract  

DSC method was used to study thermal stability of nitrocompounds. It was assumed the model to estimate stability of solid phase in which perfect solid phase is totally stable and amorphous-liquid domains connected with impurities decompose according to the kinetic model determined for the liquid phase above the melting point. The influence of sample purity on relative stability, which is k l/k s — ratio of decomposition rate constants in liquid and solid phase, at temperature 20 K below the melting point was predicted. The increase of liquid domains in solid phase causes decrease of k l/k s ratio (relative stability) at chosen temperature.

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Olive and pumpkin seed oils play a specific role in Slovenian edible oil market. That is why exact and accurate tools for assessing the oils’ quality and purity (adulteration) are needed. One of the tools is registering certain names and foodstuffs in National registers and the Register of European Union. Another tool is the analysis which can help to assess the characteristics of the oil and to classify it in categories. In the field of olive oils, this has been done excellently with the European Commission regulations. In the present work we tried to test few pumpkin seed oils for fatty acids content, trans isomers of fatty acids, composition of sterols and tocopherols. The main goal was to check the purity of the oils and understand the present situation in the field. The analytical results show that some samples are adulterated with seed oils. What can consumers benefit? From the Slovenian olive oil experience it can be concluded that the path towards better quality oils does not strictly follow analytical methods but tries to track well-established rules and definitions of quality and purity. The consumers must learn and be aware that the quality and purity can be analytically proven.

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References Cited Adayev , Vladimir Nikolayevich 2000 K voprosu o “chistote” okruzhayushchego prostranstva v predstavleniyakh nentsev i obskikh ugrov [The Issue of “Purity” of the Surrounding Environment in the Representations of Nenets

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Demszky, G. 1980: “CS”. [“R”.] Kritika 10: 18–21. Demszky G. “CS”. [“R”.] Kritika 1980 10 18 21 Douglas, M. 1989: Purity and Danger. An Analysis of the

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Abstract  

The radionuclide purity of medical (99mTc) and technical (60Co,109Cd) products was determined by γ-spectrometry. The impurities found allowed in all cases to draw conclusions on the method of production. The importance of radionuclide purity control is demonstrated.

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The preparation of high-purity magnesium oxide

I. Separation of microquantities of calcium from macroquantities of magnesium

Journal of Radioanalytical and Nuclear Chemistry
Authors: A. Dębska-Horecka, T. Pukas, and I. Stroński

Abstract  

The results are presented of an investigation with the radioactive isotope45Ca of processes of coprecipitation, crystallization and liquid—liquid extraction of calcium for the preparation of high-purity salts of magnesium.

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215 228 Noszticzius, Z., Balogh, S., Gyökérné Wittman, M., Kály-Kullai, K., Megyesi, M., Volford, A.: Permeation method and apparatus for preparing fluids containing high purity chlorine

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Activation analysis of high-purity silicon

II. Multi-element analysis: Separation scheme for 21 elements

Journal of Radioanalytical and Nuclear Chemistry
Authors: F. De Corte, A. Speecke, and J. Hoste

Abstract  

A method for the simultaneous determination of 21 elements in high purity silicon was developed by activation analysis. Extraction, ion exchange, distillation and precipitation techniques were used combined with NaI(Tl) and Ge(Li) γ-spectrometry. Attention was paid to the separation time, sensitivity and selectivity of the method.

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DSC purity determinations have become very popular today [3]. The latest edition of the Mettler software package for thermal analysis, TA72.S GraphWare, now comprises a powerful purity evaluation program. It is based on the simultaneous calculation of the mole ratio of the sum of the eutectic impurities, the melting point of the pure component, the melting point of the substance present and the linearization term. The portion of the melting curve investigated is selected appropriately.

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