Thermal analysis methodology

A comprehensive review of compositional and failure analysis of polymers, which includes many further examples of analysis of contaminants, inclusions, chemical attack, degradation, etc., was published in 2000 [2], It includes details on methodologies, sampling, and sample preparation, and microscopy, infrared spectroscopy, and thermal analysis techniques. 

In a manner similar to that just described for differential thermal analysis, DSC can be used to obtain useful and characteristic thermal and melting point data for crystal polymorphs or solvate species. This information is of great importance to the pharmaceutical industry since many compounds can crystallize in more than one structural modification, and the FDA is vitally concerned with this possibility. Although the primary means of polymorph or solvate characterization s centered around x-ray diffraction methodology, in suitable situations thermal analysis can be used to advantage. 

Most workers in the pharmaceutical field identify thermal analysis with the melting point, DTA, DSC, and TG methods just described. Growing in interest are other techniques available for the characterization of solid materials, each of which can be particularly useful to deduce certain types of information. Although it is beyond the scope of this chapter to delve into each type of methodology in great detail, it is worth providing short summaries of these. As in all thermal analysis techniques, the observed parameter of interest is obtained as a function of temperature, while the sample is heated at an accurately controlled rate. 

These parameters need to be considered for reactions that go towards the intended completion as well as for possible upsets (see section C). Measuring methodologies for determining characteristic material property values (Stoffkenngrofcen), e.g., differential thermal analysis ("DTA"), calorimetry, and adiabatic experiments, and their possible use and applications are given in the literature /1, 2, 3, 41. 

Emphasis has already been placed on the different experimental methodologies, for instance by Hume-Rothery et al. (1953) who stressed the need to use different complementary techniques in the definition of ternary or more complex systems. The necessity of combining thermal analysis with microscopic techniques was especially highlighted, for example, in the determination of solid liquid equilibria. 

The development of thermal analysis methods in materials research has led to a plethora of new methodologies since the elaboration of the first thermal method by by Le Chatelier and Robert-Austen [16,86], Thermal analysis consists of a group of techniques in which a physical property of a material is measured as a function of temperature at the same time when the substance is subjected to a controlled increase, or in some cases, decrease of temperature. Temperature-programmed techniques, such as DTA [87-89], TGA [87], DSC [53,90], TPR [91,92], and TPD [93-96], contribute to perform a more complete characterization of materials. 

Methodology for studying the polymorphism of fats, among which thermal analysis, most typically, differential scanning calorimetry (DSC), X-ray diffraction (XRD), neutron diffraction, infrared absorption spectroscopy, and nuclear magnetic resonance (NMR), are briefly mentioned here. 

Of all the methods available for the physical characterization of solid materials, it is generally agreed that crystallography, microscopy, thermal analysis, solubility studies, vibrational spectroscopy, and nuclear magnetic resonance are the most useful for characterization of polymorphs and solvates. However, it cannot be overemphasized that the defining criterion for the existence of polymorphic types must always be a non-equivalence of crystal structures. For compounds of pharmaceutical interest, this ordinarily implies that a non-equivalent X-ray powder diffraction pattern is observed for each suspected polymorphic variation. All other methodologies must be considered as sources of supporting and ancillary information, but cannot be taken as definitive proof for the existence of polymorphism by themselves. 

Thermal analysis methods are defined as those techniques in which a property of the analyte is determined as a function of an externally applied temperature. Regardless of the observable parameter measured, the usual practice requires that the physical property and the sample temperature are recorded continually and automatically and that the sample temperature is altered at a predetermined rate. Thermal reactions can be endothermic (melting, boiling, sublimation, vaporization, desolvation, solid-solid phase transitions, chemical degradation, etc.) or exothermic (crystallization, oxidative decomposition, etc.) in nature. Such methodology has found widespread use in the pharmaceutical industry for the characterization of compound purity, polymorphism, solvation, degradation, and excipient compatibility. ... 

As a result of the Process Analytical Technologies (PAT) initiative launched by the U.S. Food and Drug Administration (FDA), analytical development is receiving more attention within the pharmaceutical industry. Illustrating the importance of analytical methodologies, Thermal Analysis of Pharmaceuticals presents reliable and versatile characterization tools for the successful development of pharmaceutical products. It draws attention to the most widely applicable methods and demonstrates how to interpret the associated data. 

Keywords Hydroialciie-likc compounds Hydroxylation of Phenol Selective oxidation Structure-activity relationships In situ powder X-ray diffraction In situ DRIFT FT-IR spectroscopy Thermal analysis (TGA-DTA-EGA-TPRO) Synthesis methodology Influence of reaction parameters Ordered network Synergism... 

The number of studies in which adsorption microcalorimetry has been successfully applied to this end has increased in recent years, especially concerning the determination of the acidic function of molecular sieves, and extensive reviews of the systems investigated using this methodology have been published [1,5-14,19,78-81]. In particular, an extensive review [4] summarizes some of the most recently published results concerning applications of microcalorimetry to the study of the acid-base sites of zeolites and mesoporous materials. The efficiency of thermal analysis techniques for the characterization of the acid-base strength of zeolite materials is also discussed, as well as their ability to provide information consistent with catalytic data [4]. 

This chapter is concerned with the large family of Simultaneous Thermal Analysis (STA) techniques, in which two or more types of measurement are made at the same time on a single sample. This methodology, entailing a more complex instrument, often specially built, has been found to be essential in a variety of thermal studies, and instruments for simultaneous measurements have been constructed for more than fifty years - often as soon as it was technically possible, as the benefits of this approach were rapidly appreciated. 

The production of a radionuclide becomes the basis of activation analysis methodology. In effect, a radioisotope is formed when the nuclei of any stable isotope is exposed to a source of neutrons or any other particle. The thermal neutron reaction upon Na-23 can be used to illustrate this mode of formation ... 

Earlier TG/MS data for residual moisture in freeze-dried biological products were obtained by the continuous monitoring method of Chiu and Beattie using a DuPont 990 thermal analysis system interfaeed with a glass tee to a DuPont 21-104 mass spectrometer and the methodology... 

There are a number of different measurement techniques to determine the Tg. The most commonly used methodologies are thermal analysis techniques. Other techniques are available (such as spectral analysis and electrical characterization), but their use is limited and therefore they will not be discussed here. The three thermal analysis methods that will be discussed in this section are as follows ... 

Definitions, nomenclature, terms and sources of information in thermal analysis are to be found in refs. [15,16]. The basis of thermal analysis has recently been reviewed by Wunderlich [6], thermo-analytical instramentation, techniques and methodology by Gallagher [17] the history of thermal analysis was traced by Mackenzie [18]. Thermal analysis of polymers is described in various books [19-23] and reviews [24-28]. Thermal analysis is a powerful secondary technique. 

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