Abstract
Evolved gas analysis by mass spectrometry (EGA-MS) is well known as one of the thermal analysis methods for measuring the thermal behavior of evolved gases from a sample as a function of the temperature, which is controlled by a predetermined heating program. Presently, this method is recognized as a powerful tool for understanding the thermal pathways of materials. Since MS is a vacuum technique, in previous studies, many problems existed due to trade-offs between minimizing pyrolysate condensations and maximizing sample temperature/physicochemical measurement accuracy by efficient coupling of thermal systems with mass analyzers. In order to resolve these problems, several types of EGA-MS equipped with interface systems, which consist of capillary type and skimmer-type structures, have been developed successfully and investigated satisfactorily. This study can be summarized as follows:
1) A capillary interface structure that connects a sample chamber and a vacuum chamber for a simultaneous thermogravimetry mass spectrometry (TG-MS) system was modified to overcome condensation and memory effects and improve maintenance significantly. The effect of humidity on thermal decomposition of a sample was identified by TG-MS equipped with a specially designed furnace to prevent water condensation coupled with a humidity generator for adjusting the water vapor pressure in the atmosphere.
2) The applicability of EGA-MS using a skimmer interface system was expanded by adapting a pressure control function (PCF), which was devised for improving the serious structural disadvantage of the skimmer interface system.
3) Sample-controlled thermogravimetry (SCTG), by which the sample temperature is varied to maintain a constant rate of mass loss by controlling the furnace heating, has been successfully developed and applied to TG-MS. The demonstrated data proved that this novel feature improves the resolution and enhances the accuracy of identification and quantification, even for materials decomposing by consecutive reactions.
4) EGA-MS systems equipped with a photoionization (PI) attachment using a vacuum ultraviolet (VUV) deuterium discharge lamp as photon source have been developed successfully. It is proposed that the unique PI mass spectra obtained in real time by EGA-PIMS can satisfactorily characterize the decomposition products by only parent ions with no contribution as a result of fragmentation during ionization.
The design and construction of EGA-MS systems and their valuable applications are described briefly.
