Search Results

You are looking at 1 - 10 of 617 items for :

  • Refine by Access: All Content x
Clear All

weight and enthalpy during reaction were obvious [ 10 – 15 ]. In this paper, the thermogravimetry–differential thermal analysis (TG–DTA) and Fourier transform infrared spectroscopy (FTIR) were used to real time monitor the reaction process of

Restricted access

Abstract  

Characterization of the solid-state form (hydrate or polymorph) of a pharmaceutical active is a key scientific and regulatory requirement during development of and prior to seeking approval for marketing of the drug product. A variety of analytical methods are available to perform this task. By nature of the fundamental information it provides, TG-DTA offers advantages over other methods in regards to monitoring and quantitation of hydration state changes. In a single experiment with only a few milligrams of sample, TG-DTA perceives minor changes in phase, quantitates total water content and percent conversion, and illustrates hydrate type. All of this is accomplished without the necessity of generating time-consuming standard curves representing the differing ratios of hydrated to anhydrous forms. This study describes the use of TG-DTA to monitor and quantitate humidity induced solid–solid phase conversion of nitrofurantoin and risedronate. Percent conversion was qualitatively observed by both TG and DTA signals and quantitated by the TG.

Restricted access

Newly developed coupling systems are introduced and discussed for the combination of a simultaneous TG-DTA apparatus with a quadrupole mass-spectrometer. In the study of decomposition processes under atmospheric pressure, two-stage pressure reduction systems allow an exact gas analysis by the simultaneous operation of a mass-spectrometer up to 1550‡. For measurements under high vacuum, the pressure reduction systems are removed, and by direct viewing between test body and ion source a high sensitivity is achieved. The function of these combined units is demonstrated by means of applications in inorganic and organic chemistry.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: K. Siimer, P. Christjanson, T. Kaljuvee, T. Pehk, I. Lasn, and I. Saks

Abstract  

The thermal behaviour of MUF resins from different suppliers with different content of melamine was studied, along with the 13C NMR spectroscopic analysis of resin structure and the testing of particleboards in current production at Estonian PB factory Pärnu Plaaditehas AS. The chemical structure of resins from DMSO-d6 solutions was analysed by 13C NMR spectroscopy on a Bruker AMX500 NMR spectrometer. The melamine level in different MUF resins is compared by the ratios of carbonyl carbon of urea and triazine carbon of melamine in 13C NMR spectra. Curing behaviour of MUF resins was studied by stimultaneous TG-DTA techniques on the Labsys™ instrument Setaram. The shape of DTA curves characterisises the resin synthesis procedure by the extent of polymerisation of UF and MF components and is in accordance with structural data.

Restricted access

A combination system of thermogravimetric/differential thermal analysis (TG-DTA) and Fourier-transform infrared absorption spectroscopy (FT-IR) was described. This simultaneous TG-DTA/FT-IR technique gave spectroscopic and weight loss information about the thermal degradation process of engineering polyesters; poly(ethylene terephthalate)(PET) and poly(butylene terephthalate)(PBT). The evolved gases from PET were benzoic acid, carbon dioxide and carbon monoxide, while those from PBT were terephthalic acid esters and benzoic acid esters.

Restricted access

Summary An odorless woodceramics (CH800), which was prepared by carbonizing chicken wastes with phenolic resin, was characterized by XRD and thermal analysis. CH800 was found to consist mainly of amorphous carbon (non-graphitizing carbon) as studied by XRD. Differing from carbonized chicken waste, CH800 was completely free of unfavorable smell. The source of strong smell of carbonized chicken waste was studied by using TG-DTA combined with EGA technique using gas chromatography and mass spectrometry (TG-DTA/GC-MS). As a result, it was found that CH800 was completely free of compounds having strong smell, i.e., ethanol, acetonitrile, pyridine, styrene, benzonitrile and benzofuran, whereas carbonized chicken waste contained all of these compounds.

Restricted access

To improve the separation of the dihydrate and hemihydrate phases, different sample masses, heating rates and crucibles were used. A TG-DTA method was developed for the determination of water evolved from CaSO4·xH2O. The new crucible introduced for the Q-1500D MOM derivatograph gives a possibility for the evolved water to be determined independently from the TG and DTA curves.

Restricted access

Abstract  

A mixed crystal of urea–thiourea was grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized by thermogravimetric–differential thermal analysis (TG–DTA), UV and FTIR spectroscopic analyses. A fitting decomposition pattern for the title compound was formulated on the TG curve which shows a two stage weight loss between 200 and 750 °C. In this temperature range DTA curve shows exothermic peaks supporting the formulated decomposition pattern. The UV and FTIR spectra show the characteristic absorption, vibration frequencies due to urea–thiourea mixed crystals. Detailed structural analysis of the compound is under progress.

Restricted access

Abstract  

The successful combination of microscopy with thermogravimetry-differential thermal analysis is reported. Simultaneous use of all three techniques is made possible by custom fitting a quartz glass window into the furnace of a commercially available TG-DTA. The quartz window enabled direct observations from a microscope mounted above the furnace throughout the entirety of the thermal analytical experiments. Several examples are provided for the use of this combined system for evaluating dehydrations, degradation and phase conversions in pharmaceutical materials. In some examples, microscopy provided information not accessible from the thermal analytical data alone. In others, the thermal analytical data was more informative than the microscopy.

Restricted access

A completely new simultaneous digital and symmetrical TG-DTA thermoanalyzer, called TAG 24, has been designed.

Restricted access