Mass spectrometry with thermogravimetry

Keen and co-workers [20] used EGA to monitor the evolution of additives from rubber and polymers in order to evaluate the effectiveness of encapsulated BHT antioxidant from polyisoprene. The technique involves the coupling of a thermogravimetry mass spectrometry with oxidative DSC. 

The number of experimental factors which influence the results increases considerably when thermogravimetry is combined with other techniques such as DTA, gas chromatography46, mass spectrometry, X-ray etc. A systematic discussion of all these additional factors would lead too far, therefore only a representative example will be discussed here. One of the often-applied multiple techniques is the combination TG-DTA. Besides the actual thermal reactions of the sample, the important factors in DTA are the heat capacity and the thermal conductivity of the sample. Optimum heat transfer is required for such thermoanalytical measurements therefore the shape of the sample and its contact with the crucible is of special importance. 

Thermoanalysis methods such as pyrolysis-gas chromatography-mass spectrometry [GC-MS] and thermogravimetry mass spectrometry have been used to characterise hydrocarbon sludges from petrochemical plants and polluted soils [26,27]. In combination with conventional extraction and supercritical fluid extraction followed by [ GC-MS ], over 100 constituents were identified in samples. White et al. [28] also applied pyrolysis-[GC-MS] to the determination of hydrocarbons and showed that the analysis can be complicated by the presence of natural organic matter. White [28] inferred the presence of biogenic compounds in Alaskan soil. 

A systematic study of both physical and chemical aspects in plastics pyrolysis was launched in the Cycleplast project [6]. Thermal degradation of commodity polymers, including kinetic factors and mechanism, were systematically investigated by Professor Bockhom and collaborators, using thermogravimetry, linked with mass spectrometry, as well as closed loop laboratory-scale pyrolysis reactors. The resulting kinetic parameters are discussed further. 

When decomposition is evidently not simple, with two or more processes being observed to overlap, sufficient information must be obtained to enable the contributions from each of the participating reactions, including secondary reactions between products, to be distinguished. Use of mass spectrometry or Fourier transform infrared spectroscopy coupled with thermogravimetry (see below) allows the evolution of individual gaseous species to be measured as functions of time or temperature. 

Baffin, G. and Grenier-Loustalot, M.-F. (2004) Coupling thermogravimetry with cold trap/gas chromatography and mass spectrometry. Spectra Analyse, 33 (241), 36-43. 

Thermogravimetry/mass spectrometry was used to determine adsorptive capacity of several commercially available activated carbons produced from coal, coconut, and petroleum pitch precursors. The range of their N2 BET surface areas was between 400 to 2000 m /g. Although, carbons with high adsorption capacity contained similar C, N, and O contents, proximate analyses, surface areas and micropore volumes, no significant correlations were found between chemical and physical properties and the NO, adsorptive capacity. One possibly important characteristic of the carbons correlated with NO, adsorption capacity was specific and narrow pore size distribution with an effective pore diameter of 0.56 nm. 

Applying conventional (thermogravimetry TG Differential thermal analysis DTA evolved gas detection EGD) and combined (thermogravimetry-mass spectrometry TG-MS) techniques, the pCD inclusion complexes with thymol and Lippia sidoides Cham EO (LsCEO) extract produced by kneading method were characterized. Its formations were detected through released gas... 

Thermogravimetry-mass spectrometry was done with a Perkin Elmer TAS 2 TGA connected by a capillary transfer line to a Hewlett Packard mass selective detector. A heating rate of 40 C7min was used so that the volatiles would rapidly desorb from the sample. Helium was used as a carrier gas at a pressure of 40 psi. The time traces of water and NMP were done at mass to charge ratios of 18 and 99 respectively. 

This study combines a thermal analysis technique -thermogravimetry with atmospheric pressure chemical ionization mass spectrometry and applies the combined technique to the third question. The literature contains references relating to the analysis of styrene butadiene copolymers using thermal analysis techniques (1-5). Pyrolysis - mass spectrometry (5) and vacuum thermogravimetry - mass spectrometry (7) have also been used to investigate polymers such as polystrene and styrene butadiene rubber. 

Reports on the detailed thermal behaviour of PEEK/HAp composites [as well as other polymer/HAp (nano)composites] are scarce in the literature. Advanced thermal analysis methods, e.g., modulated temperature differential scanning calorimetry (MTDSC) or hyphenated thermoanalytical methods such as thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR) or mass spectrometry... 

The well-known advantages of a quadrupole mass spectrometer (QMS) as a universal gas analysis instrument have often been used in combination with thermoanalytical methods. Especially interesting is the coupling of a mass spectrometry (MS) with thermogravimetry (TG,TGA) or simultaneous TG with Differential Scanning Calorimetry (DSC). 

Spectrometric methods, especially mass sf>ectrometry (MS) and Fourier transform infrared spectrometry (FilR) have been used, often coupled with thermogravimetry. For molecules that are pwlar and of low molar mass, FTIR is particularly useful. For nonpwlar molecules and those of higher molar mass, MS is more adaptable. There are problems, however, in interfacing the thermal analysis instrument operating at atmospheric pressure to the MS operating imder vacuum. This is discussed in Topic F3. 

Figure 8.21 Thermogravimetry analysis coupled with mass spectrometry of Tio ysOHj,sF,s compound showing the water and T1F4 evolutions. Reproduced with the permission of ACS or American Chemical Society...

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