Thermal Analysis Techniques (thermal + analysis_techniques)

Distribution by Scientific Domains

Selected Abstracts

Schiff base substitute polyphenol and its metal complexes derived from o -vanillin with 2,3-diaminopyridine: synthesis, characterization, thermal, and conductivity properties

smet Kaya
Abstract Poly-2,3 - bis[(2-hydroxy-3-methoxyphenyl)methylene]diamino pyridine (PHMPMDAP) that a new Schiff base polymer has been synthesized and characterized by spectroscopy, elemental, and thermal analyses techniques. This azomethine polymer was found to form complexes readily with Cu(II), Zn(II), Co(II), Pb(II), and Fe(II). From IR and UV-Vis studies, the phenolic oxygen and imine nitrogen of the ligand were found to be the coordination sites. Thermogravimetric analysis (TGA) data indicate the polymer to be more stable than the monomer. The structure of the polymer obtained was confirmed by FT-IR, UV-Vis, 13C-NMR, and 1H-NMR. Characterization was undertaken by TGA, size exclusion chromatography (SEC), and solubility tests. Also, electrical conductivities of PHMPMDAP and polymer,metal complexes are measured by four probe technique. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Coordination complexes of functionalized pyrazines with metal ions: reagents for the controlled release of flavourant molecules at elevated temperatures

Colin Baillie
Abstract The potential for stabilization of volatile flavourant molecules such as functionalized pyrazines by coordination to metal ions, and the application of the resultant coordination complexes as controlled release agents at elevated temperatures were explored. New complexes containing the flavourant molecules 2,3,5-trimethylpyrazine (TMP), 2-ethyl-3-methylpyrazine (EMP) and 2-acetylpyrazine (ACP) with copper(II) and copper(I) salts were prepared and structurally characterized. Representative examples of known copper(II) and calcium(II) complexes containing pyrazine carboxylic acids were also prepared. The complexes were examined by thermal analysis techniques and demonstrated, by a combination of thermogravimetric (TGA) and pyrolysis GC,MS analyses, to act as convenient reagents for the release of the parent pyrazine at elevated temperatures. Thus, pyrolysis GC,MS revealed that the complex [Cu3Cl3(EMP)2]n cleanly releases EMP in 96.5% selectivity at 200 °C. Of particular significance is that the calcium complex [Ca(3-aminopyrazine-2-carboxylate)2·H2O], under ramped pyrolysis conditions, was shown to undergo decarboxylation prior to the release of 2-aminopyrazine (AMP), as essentially the only volatile component, in the temperature range 600,800 °C. This finding provides a precedent for the application of complexes of pyrazinecarboxylate salts with metal ions (of which an almost infinite number of combinations is potentially available) as controlled release agents of the parent pyrazine molecule at elevated temperatures, suitable for exploitation by the foodstuffs, flavour and fragrance industries. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Molecular Recognition in Partially Folded States of a Transporter Protein: Temperature-dependent Specificity of Bovine Serum Albumin

Debapriya Banerjee
The specificity of molecular recognition of a transporter protein bovine serum albumin (BSA) in its different partially folded states has been studied. In order to avoid complications due to chemical denaturation, we have prepared thermally induced partially folded states of the protein. The partially folded states have been structurally characterized by circular dichroism and differential thermal analysis techniques. The change in the globular structure of the protein as a consequence of thermal unfolding has also been characterized by dynamic light scattering. Steady state, picosecond-resolved fluorescence and polarization gated spectroscopies on the ligands (DCM, LDS 750) in the protein reveal the dynamics of the binding sites and the specificity of ligand binding of BSA. Picosecond resolved Förster resonance energy transfer studies on the donor DCM and acceptor LDS 750 confirm that the specificity of ligand binding in the binding site is maintained up to 70°C. At 75°C, the protein loses its specificity of recognition at the aforesaid site. [source]

Solid-Phase Extraction of Metoprolol onto (Methacrylic acid- ethylene glycol dimethacrylate)-based Molecularly Imprinted Polymer and Its Spectrophotometric Determination

Mohammad Saber Tehrani
Abstract A new adsorbent for molecularly imprinted solid phase extraction (MISPE) of metoprolol was synthesized using methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linking agent causing a non-covalent, bulk, thermal radical-polymerization. Control polymer (non-imprinted polymer) was prepared under well defined conditions without the use of metoprolol. The synthesized polymers were characterized by IR spectroscopy, X-ray diffraction and thermal analysis techniques. This polymer was used for the rapid extraction and preconcentration of metoprolol from real samples prior to spectrophotometric determination. Extraction efficiency and the influence of flow rates of sample and stripping solutions, pH, type of eluent for elution of metoprolol from polymer, break through volume and limit of detection were studied. The detection limit of the proposed method is 0.4 ng·mL,1. The method was applied successfully to the recovery and determination of metoprolol in tablets, human urine and plasma samples. [source]