TG-FTIR: The combination for outstanding analytical results
Albrecht Rager BRUKER OPTIK GmbH, Rudolf-Plank-Straße 23, D-76275 Ettlingen
Thermogravimetric analysis (TG) follows changes in mass of the sample as a function of temperature whereas TG gives information about composition and thermal behavior of the sample, an identification of gases released from the sample during thermal treatment cannot be performed by thermal analysis itself. For this purpose, coupling a spectroscopic method such as Fourier-Transform - Infrared (FT-IR) spectroscopy is an excellent solution. Proper optimization of the TG, the FT-IR and the interface yields to a combination, who guarantees for outstanding results. Certain points are discussed by examples:
Infrared spectroscopy, a classical technique, depends upon the interaction of infrared radiation with the vibrating dipole moments of molecules. With the exception of homonuclear diatomics and noble gases, each vapor phase spectrum is characteristic for a single compound. Qualitative evolved gas analysis followed by digital library search makes identification a child's play.
FT-IR spectroscopy is a suitable method for the analysis of gas mixtures which usually occur during thermal decomposition. An optimally coupled TG-FT-IR system is necessary in order to analyze in detail complex and in particular overlapping decomposition steps. For complex mixture analysis, subtraction routines allow to separate known compounds from the mixture spectrum for further library identifications and factor analysis allowing even quantitative considerations of overlapping spectra.
Pulse Thermal analysis® methods expands the possibilities of quantitative TG-FTIR into new dimensions. By a simple "mouseclicks", the amount of a released compounds are defined.
The vacuum-tight construction of the thermal micro balance and the gas cell, allows to evacuate both systems together. Lowered pressures offers a further parametric variation and therefore a more optimised TG-step separation. IR-Identification of larger fragments leads to more structural information on the investigated sample.
zurück