Mass Spectrometry for Semiquantitative Analysis of Thermal Decomposition: A Methodological Case Study on the Pyrolysis of a (CH3)SiO1.5 Hybrid Gel

Rationale: The thermal decomposition of (CH3)SiO1.5 gels has been systematically investigated by TG-MS, revealing a complex temperature-dependent evolution of gaseous species. This work demonstrates that the TG-MS analysis, coupled with rigorous data processing, allows to set up an insightful methodology to evolve from a qualitative monitoring tool into a quantitative approach, opening new avenues for thermal and compositional analysis. Methods: By combining ion current integration with fragmentation pattern analysis, a semiquantitative determination of the gas-phase composition was achieved, enabling correlation between individual species release, reaction mechanisms, and total mass loss. Results: The stoichiometric analysis of the evolved products has allowed the reconstruction of the gel's initial chemical composition solely from MS data, offering a powerful alternative to conventional structural characterization. The excellent agreement between measured (17.28%) and MS-derived (17.24%) mass loss confirms the reliability of the approach, considering also that the thermal decomposition of the methylsiloxane hybrid gel investigated is representative of a complex system generating numerous overlapping volatile species. Conclusions: The proposed study investigates the potentialities of the TG-MS analysis in setting up a powerful tool for the study of thermal decomposition of hybrid organic-inorganic materials. The proposed approach opens new perspectives for thermal process investigations and for the compositional analysis of materials where conventional characterization methods are limited or unavailable.