Isothermal calorimetry methods

Experimental methods for measuring plant respiratory heat rates, gas exchange rates, and relating these to growth rates and stress responses have been much refined over the past decade. Examples of experimental methods currently in use for specific applications are outlined here. 

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As can be seen, the enthalpies of different apoxy-amine systems, according to different authors, lie in a rather narrow range (100-118 kJ per mole of epoxy groups, i.e. close to the heat of the epoxy ring opening). These data confirm the above conclusion as to the small total contribution of the donor-acceptor interactions in the epoxyamine systems to the observed integrated value of the heat release and the possibility of the application of the isothermal calorimetry method to the reaction kinetic studies. 

The study and control of a chemical process may be accomplished by measuring the concentrations of the reactants and the properties of the end-products. Another way is to measure certain quantities that characterize the conversion process, such as the quantity of heat output in a reaction vessel, the mass of a reactant sample, etc. Taking into consideration the special features of the chemical molding process (transition from liquid to solid and sometimes to an insoluble state), the calorimetric method has obvious advantages both for controlling the process variables and for obtaining quantitative data. Calorimetric measurements give a direct correlation between the transformation rates and heat release. This allows to monitor the reaction rate by observation of the heat release rate. For these purposes, both isothermal and non-isothermal calorimetry may be used. In the first case, the heat output is effectively removed, and isothermal conditions are maintained for the reaction. This method is especially successful when applied to a sample in the form of a thin film of the reactant. The temperature increase under these conditions does not exceed IK, and treatment of the experimental results obtained is simple the experimental data are compared with solutions of the differential kinetic equation. 

Foubert, I., Vanrolleghem, P.A. and Dewettinck, K. (2003). A differential seanning calorimetry method to determine the isothermal crystallization kinetics of cocoa butter. Thermochemica Acta, 400 131-142. 

Chrzanowski FA, Ulissi LA, Fegely BJ, Newman AC. Preformulation excipient compatibility testing, application of a differential scanning calorimetry method versus a wet granulation simulating isothermal stress method. Drug Dev Ind Pharm 1986 12 783-800. 

Velazquez-Campoy, A., Leavitt, S. A., and Freire, E. (2004) Characterization of protein-protein interactions by isothermal titration calorimetry. Methods Mol. Biol. 261, 35-54. 

Lewis EA, Murphy KP (2005) Isothermal titration calorimetry. Methods Mol Biol 305 1-15... 

A direct experimental method that does not rely on approximations and assumptions has been reported by Ahmed et It is based on a combination of DSC with isothermal calorimetry and powder X-ray diffraction. It is particularly useful for the detection of low amounts of amorphous material in allegedly crystalline drug products. 

Lachinov and co-workers [52] have performed a more detailed study of the kinetics of block radical polymerisation of perfluoroalkylmethacrylates (FMA) in the solid state. The main method of investigation of the kinetics of FMA polymerisation was isothermic calorimetry [58]. Due to the absence of data on the heat effects of their polymerisation in the reference literature, these values were measured [52]. The values of AQ and glass transition point (T ) of polymers formed are shown in Table 8.3. Obviously heat of polymerisation of monomers of the fluoroacrylate sequence is quite close to heat of polymerisation of non-substituted monomers of the AMA sequence [59], and a significant influence of the length of the fluoroalkyl radical on this parameter is absent [52]. In accordance with the Polyani-Semenov rule, the present result makes it possible to consider that chain propagation constant of FMA with the accuracy of the pre-exponential multiplicand being equal to each other [57]. 

In differential scanning calorimetry (DSC), the sample is not heated at a constant rate, but a definite quantity of heat is either added or taken away isothermally. This method is particularly suited to measure the heats of fusion at crystallization or to follow the course of crystallization at a given temperature. 

The q values (Table 1.8) calculated from the water adsorption isotherms are similar to the Q values (Table 1.9) obtained using the calorimetry method. Certain differences between these values can be caused by different conditions of sample preparation and subsequent rehydration effects discussed earlier. 

Why is it that with isothermal calorimetry we can deterntine two thermodynamic parameters (K, and AH°), while titrations involving other methods give only one thermodynamic parameter (KJ ... 

Thermal methods play a key role in both the identification and the characterization of solid forms. A thermal method can be defined as a method where the heat flow is measured as a function of an externally varied parameter. If this parameter is, for example, time and all other parameters are held constant, the method is called isothermal calorimetry. In solution calorimetry, a solid is dissolved in a particular solvent and the associated heat of dissolution is measured. Probably the most frequently used thermal technique is differential scanning calorimetry (DSC) [8], where temperature is varied and the associated heat flow is measured. 

Detailed reviews have been published on calorimetric design, on isothermal calorimetry,2 and on adiabatic calorimetry. The emphasis in the present account is on automatic methods for measurements of heat capacity and enthalpies of phase changes by adiabatic calorimetry. 

Holdgate, G.A. (2010) Isothermal titration calorimetry and differential scanning calorimetry. Methods in Molecular Biology, 572,101 133. 

The results of the complex kinetic study of the formation of the mesophase in PDES, including a smdy of growth of the lamellar structure by an optical method and the integral kinetics of formation of the mesophase by isothermal calorimetry, are shown in Figs. 4.9 and 4.10 [30]. The linear rate of growth of mesomorphic domains (bright bands) remains constant in a relatively long time... 

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