Quantitative analysis, differential scanning calorimetry

Thermal analysis is a term used to cover a group of techniques in which a physical property of a substance and/or its reaction product(s) is measured as a function of temperature. This experiment is confined to the area of differential thermal analysis (DTA) and, more specifically, its quantitative development, differential scanning calorimetry (DSC) [1-15]. 

Based on the structure-related addition schemes for the thermal properties, it should, for example, be possible to quantitatively generate differential scanning calorimetry curves for polymers, copolymers and their mixtures. With easy access to the data bank, it should be possible for thermal analysts to compare their newly measured DSC curves with the computer generated standard curves for on-line analysis of macromolecules. 

This chapter describes various aspects of thermal studies conducted on CaS04 2H20 and a and P forms of CaS04 /2H20, using differential thermal analysis, differential scanning calorimetry, and thermogravimetry. The effect of environmental conditions on the quantitative deterioration of the various calcium sulfate compounds is also examined. The development of more recent techniques such as controlled reaction thermal analysis is also presented.t ... 

The techniques referred to above (Sects. 1—3) may be operated for a sample heated in a constant temperature environment or under conditions of programmed temperature change. Very similar equipment can often be used differences normally reside in the temperature control of the reactant cell. Non-isothermal measurements of mass loss are termed thermogravimetry (TG), absorption or evolution of heat is differential scanning calorimetry (DSC), and measurement of the temperature difference between the sample and an inert reference substance is termed differential thermal analysis (DTA). These techniques can be used singly [33,76,174] or in combination and may include provision for EGA. Applications of non-isothermal measurements have ranged from the rapid qualitative estimation of reaction temperature to the quantitative determination of kinetic parameters [175—177]. The evaluation of kinetic parameters from non-isothermal data is dealt with in detail in Chap. 3.6. 

If the observed AH is positive (endothermic reaction), the temperature of the sample will lag behind that of the reference. If the AH is negative (exothermic reaction), the temperature of the sample will exceed that of the reference. Owing to a variety of factors, DTA analysis is not normally used for quantitative work instead, it is used to deduce temperatures associated with thermal events. It can be a very useful adjunct to differential scanning calorimetry, since with most instrumentation DTA analysis can be performed in such a manner that corrosive... 

In many respects, differential scanning calorimetry (DSC) is similar to the DTA method, and analogous information about the same range of thermal events can be obtained. However, DSC is far easier to use routinely on a quantitative basis, and for this reason it has become the most widely used method of thermal analysis. The relevance of the DSC technique as a tool for pharmaceutical scientists has been amply documented in numerous reviews [3-6,25-26], and a general chapter on DSC is documented in the U.S. Pharmacopeia [27]. 

Analysis of Major Elements. Major elements were determined quantitatively by neutron activation analysis at the University of Toronto SLOWPOKE reactor. This technique was chosen because the available sample size was small. Differential scanning calorimetry with a Perkin-Elmer DSC-1B was used to establish the plaster composition further and to investigate its thermal behavior. 

Thermal analysis techniques (differential thermal analysis (DTA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and evolved gas analysis (EGA)) provide qualitative, semiquantitative, and in special cases, quantitative measurements of the energetic evolution of nanophase materials on heating. Variation of the heating rate and the atmosphere surrounding the sample provide additional information. Some examples are given below in the context of specific systems. 

Anonymous Differential Scanning Calorimetry, A Quantitative Technique for Differential Thermal Analysis. MPL-6632, Perkin-Elmer Instrument Division, Norwalk, Conn. (1964). 

Differential thermal analysis was the first major improvement developed over simple melting point analysis, and in countless studies was used to determine the characteristic temperature ranges associated with a variety of thermally induced reactions. Differential scanning calorimetry subsequently effectively replaces the DTA method, primarily because of its ability to yield quantitative information regarding the magnitude of the heat associated with the thermal reaction. For this reason, DSC has become accepted as the most widely used method of thermal analysis for the pharmaceutical industry. 

Grentzer, T. H. Holsworth, R.M. Provder, T. Kline, S. "Quantitative Reaction Kinetics by Differential Scanning Calorimetry", Proceedings of the Tenth North American Thermal Analysis Society Conference, (Oct. 26-29, 1980), Boston, Mass., 269. 

Differential scanning calorimetry, DSC, is a variant of differential thermal analysis. With DSC, the required heat for the transition is added or removed at the transition temperature. Thus, this method is particularly suited to quantitatively measuring heats of fusion or crystallization, as, for example, with crystallization at a given temperature. 

Mathematical modeling of the cure process coupled with the automation of various thermal analytical instruments and Fourier Transform Infrared Spectroscopy (FT-IR) have made possible the determination of quantitative cure and chemical reaction kinetics from a single dynamic scan of the reaction process. This paper describes the application of FT-IR, differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) in determining cure and reaction kinetics in some model organic coatings systems. 

Sects. 4.2-4A. Intermediate between thermometry and calorimetry is differential thermal analysis, or DTA. In this technique transition temperature information is derived by the qualitative changes in heats of transition or heat capacity. As the instrumentation of DTA advanced, quantitative heat information could be derived from temperature and time measurements. The DTA has in the last 50 years increased so much in precision that its applications overlap with calorimetry, as is shown in the discussion of the different forms of differential scanning calorimetry, DSC (Sects. 4.3 and 4.4). 

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