Transitions isothermal microcalorimetry

The evolution in calorimetry technology has also led to the development of protocols for quantitative analysis (Buckton and Darcy 1999). Fiebich and Mutz (1999) determined the amorphous content of desferal using both isothermal microcalorimetry and water vapour sorption gravimetry with a level of detection of less than 1 per cent amorphous material. The heat capacity jump associated with the glass transition of amorphous materials MTDSC was used to quantify the amorphous content of a micronised drag substance with a limit of detection of 3 per cent w/w of amorphous... 

To fully understand the performance of amorphous materials, it is necessary to be able to measure the molecular mobility of the samples on interest. This is because at temperatures as far as 50 K below the glass transition temperature, pharmaceutical glasses exhibit significant molecular mobility that can contribute to both chemical and physical instability.The main techniques that have been developed for monitoring molecular motions in amorphous materials are nuclear magnetic resonance (NMR) and calorimetric techniques (e.g., DSC and isothermal microcalorimetry). Average molecular relaxation times and relaxation time distribution functions obtained from these... 

Quantitative investigation of recognition of this pair of liposomes was performed with isothermal titration microcalorimetry (ITC). It has been found that one-to-one binding between adenine and barbituric acid in the lipid/water/lipid interface occurs. However at T= 58°C, above the main lipid phase transition, the situation is different and no liposomal binding is detected. This is mainly due to the molecular disorder within the bilayer (liquid-disordered/liquid ordered phase coexistence) that limits the capacity of complementary moieties to bind, due to the weakening of the hydrogen bonds at these high temperatures. 

Llewellyn and Maurin (2005) demonstrated that gas (nitrogen and argon) adsorption microcalorimetry can be used a powerful technique for depth examination of the surface state of adsorbents and a minute following of adsorption mechanisms such as phase changes and transitions. The use of this technique in parallel to the measurements (and appropriate analysis) of the adsorption isotherms of the same gases, and DSC and/or NMR cryoporometry measurements can provide deeper insight into the interfacial phenomena over a broad temperature range. 

Adapted from Steinmann, W., Walter, S., Beckers, M., Seide G., Gries, T., 2013. Thermal analysis of phase transitions and crystallization. In Elkordy A.A. (Ed.), Polymeric Fibers, Applications of Calorimetry in a Wide Context— Differential Scanning Calorimetry, Isothermal Titration Calorimetry and Microcalorimetry. ISBN 978-953-51-0947-1. InTech. Rijeka, pp. 277-306. Available from http //www.intechopen.com (accessed 7.7.15). 

In Fig. 1.21a, the differential heats of adsorption of CO on H—BEA zeolite and on MFI-Silicalite are reported as a function of the adsorbed amounts. Volumetric isotherms are illustrated in the figure inset. In both cases the adsorption was fully reversible upon evacuation of the CO pressure, as typical of both physical and weak, associative chemical adsorption. For H-BEA a constant heat plateau at 60kJ mol was measured. This value is typical of a specific interaction of CO with coordinative unsaturated Al(III) atoms, as it was confirmed by combining adsorption microcalorimetry and molecular modeling [73, 74, 78, 89] Note that the heat value was close to the heat of adsorption of CO at cus Al(III) sites on transition catalytic alumina, a typical Lewis acidic oxide [55, 73], Once saturated the Al(III) defects, the heat of adsorption started decreasing down to values typical of the H-bonding interaction of CO with the Br0nsted acidic sites (- 30 kJ mol , as reported by Savitz et al. [93]) and with polar defects, either confined in the zeolite nanopores or at the external surface. 

---