Thermal gravimetry-mass spectrometry

Pyrolysis Gas Chromatography—Mass Spectrometry-Computer and Thermal Gravimetry—Mass Spectrometry—Computer Methods... 

Crystalline products with the structure of AIPO4-II have been produced using four different amines as structure-directing species. A method for quantifying the amount of amine in the precursors has been developed. This involves the use of thermal desorption/mass spectrometry in combination with thermo-gravimetry. This method also provides information as to the distribution of the water within the structure. 

A primary method [2] is one that is capable of operation at the highest metrological level, which can be completely described and for which a complete uncertainty statement can be produced in SI units. The amount of substance can be measured either directly, without reference to any other chemical standard, or indirectly, by use of a ratio method which relates the amount of unknown entity X to a chemical standard. Primary direct methods, such as gravimetry and certain electrochemical and thermal methods are the exceptions in chemistry, as the majority of measurements are made indirectly by comparison with other pure substance RMs as discussed above and below. These ratio methods include isotope dilution mass spectrometry and chromatographic and classical methods. Hence the importance of pure substance RMs. 

The thermal characterisation of elastomers has recently been reviewed by Sircar [28] from which it appears that DSC followed by TG/DTG are the most popular thermal analysis techniques for elastomer applications. The TG/differential thermal gravimetry (DTG) method remains the method of choice for compositional analysis of uncured and cured elastomer compounds. Sircar s comprehensive review [28] was based on single thermal methods (TG, DSC, differential thermal analysis (DTA), thermomechanical analysis (TMA), DMA) and excluded combined (TG-DSC, TG-DTA) and simultaneous (TG-fourier transform infrared (TG-FTIR), TG-mass spectroscopy (TG-MS)) techniques. In this chapter the emphasis is on those multiple and hyphenated thermogravimetric analysis techniques which have had an impact on the characterisation of elastomers. The review is based mainly on Chemical Abstracts records corresponding to the keywords elastomers, thermogravimetry, differential scanning calorimetry, differential thermal analysis, infrared and mass spectrometry over the period 1979-1999. Table 1.1 contains the references to the various combined techniques. 

Primary Reference Material PRM a reference material certified with (a) primary method(s). In practice such materials are mainly pure substances, manufactured materials, rarely matrix materials as already explained above. PRMs of matrix materials are very limited in number. NIST has available some CRMs certified with thermal ionisation-isotope dilution mass spectrometry (TMDMS) which has been classified by the Comite Consultatif sur la Quantite de Matiere (CCQM) of BIPM as primary method. PRMs also exist for gas analysis. The Netherlands Meet Instituut (NMI) in Delft, The Netherlands has available several primary gas RMs prepared by gravimetry... 

Classical or wet chemistry analysis techniques such as titrimetry and gravimetry remain in use in many laboratories and are still widely taught in Analytical Chemistry courses. They provide excellent introductions to the manipulative and other skills required in analytical work, they are ideal for high-precision analyses, especially when small numbers of samples are involved, and they are sometimes necessary for the analysis of standard materials. However, there is no doubt that most analyses are now performed by instrumental methods. Techniques using absorption and emission spectrometry at various wavelengths, many different electrochemical methods, mass spectrometry, gas and liquid chromatography, and thermal and radiochemical methods, probably account for at least 90% of all current analytical work. There are several reasons for this. 

It must be emphasised that infrared and Raman spectroscopy should not be used to the exclusion of other techniques such as H and C nuclear magnetic resonance, which are particularly useful characterisation techniques. Other useful techniques are mass spectroscopy, ultraviolet-visible spectroscopy, chromatography, thermo-analytical techniques (such as differential scanning calorimetry (DSC), thermal gravimetry (TG) etc.), or combined techniques such as GC-MS (gas chromatography combined with mass spectrometry)... 

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