Thermogravimetric analysis, sublimation

The thermal degradation of TsHs and other TsRs species (R = Me, /Bu, nCsHiy, Ph) in air and an inert atmosphere has been studied by thermogravimetric analysis and shows that for TsHs incomplete sublimation tends to occur, and, in air, oxidation competes with volatalization. ... 

Early devices fbr thermogravimetric analysis were limited in precision and convenience when compared with DTA or DSC equipment. Now devices for simultaneous DSC and TG are on the market which can operate at high temps in reactive atms permitting the simulation of high temp reactions on a micro scale. The use of TG for the study of reaction kinetics was described in Sect 5.3.3. An exptl study of the sublimation of ammonium perchlorate was published by Jacobs and Jones (Ref 25). Similar techniques should find application in the study of other propint systems. The product gases have been collected for further analysis using gas chromatography and mass spectrometry... 

Thermogravimetric analysis (TGA) measures the change in mass of a sample as a function of temperature. It therefore provides information on the presence of volatile components, in the present context particularly solvents or water, which form the basis of solvates or hydrates respectively, as well as processes such as decomposition and sublimation. 

Polymer (a) has number average molecular weight of 7.200, and the thermogravimetric analysis is given in Fig. 72. The major weight loss occurs between 500 and 600°C. The analysis of volatile products at different temperatures has been performed (Table 25). Some products sublimed and, according to mass spectral analysis, they may correspond to the chain fragments... 

Figure 4.64. Top Thermogravimetric analysis of organomagnesium CVD precursors, indicating the dependence of molecular structure on its decomposition temperature. Bottom Tandem TGA/DSC analyses showing a single endothermic event (sublimation) that coincides with the mass loss. The Ugand abbreviations are dpm = 2,2,6,6-tetramethyl-3,5-heptanedionate, TMEDA = N, N, N, tF-tetramethylethylenediamine, hfa = l,l,l,5,5,5-hexalluoro-2,4-pentanedione, HTEEDA = H(W, N, N, IV -tetraethylethylene diamine). Reproduced with permission from Chem. Mater. 2005, 77(23), 5697. Copyright 2005 American Chemical Society.

Thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD) of la showed that two third of acetone molecules can be removed at lower temperature of 70 °C and induced rearrangement of host to lb form. Whereas the remaining one third of acetone molecules can be removed at 225 °C to yield a pure apohost phase Ic. Thus, lb exhibits surprisingly remarkable thermal stability for a molecular assembly. Barbour and coworkers obtained single crystal of apohost phase (Ic) by sublimation at 270 °C and the follow-up single crystal diffractirMi studies reveal that the structure of Ic is similar to that of lb. Since the crystals were grown rmder vacuum, the discrete void spaces in Ic remain empty [6]. 

Minli, X., Ziemba, M. T. and Maurin, M. Sublimation characterization and vapor pressure of an FnV nonnucleoisde reverse transcriptase inhibitor using thermogravimetric analysis. AAPS PharmSciTech. 4(23) l-9, 2003.www.pharscitech.org, 2003. 

Among the most commonly used thermoanalytical techniques is thermogravimetric analysis (TGA), which provides information about the mass variations resulting from a physical (sublimation, evaporation, condensation) or chemical (degradation, decomposition, oxidation) change as a function of time and/or temperatiue [12]. 

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