Calorimetry isothermal microcalorimetry

Contact angle measurements Isothermal microcalorimetry Gravimetric sorption Inverse gas chromatography Differential scanning calorimetry Thermogravimetric analysis Isothermal microcalorimetry Infra red analysis X-ray diffraction... 

Table 2 Comparison of differential calorimetry and isothermal microcalorimetry (4)...

There are a number of excellent books that provide information on pharmaceutical thermal analysis but many do not include sections on isothermal microcalorimetry. Probably the most useful textbook in print is The Handbook of Thermal Analysis. Vol 1 Principles and practice, edited by ME Brown, Elsevier Science (Amsterdam), 1998, which comprehensively covers all aspects of thermal analysis. A more specialised, but now out of print, text is Biological Microcalorimetry, edited by AE Beezer, Academic Press (London), 1982 and an excellent chapter can be found in Principles of Thermal Analysis and Calorimetry, edited by PJ Haines, RSC (Cambridge), 2002. The subject of pharmaceutical uses of DSC is more widely covered with excellent texts including Biocalorimetry, edited by JE Ladbury and BZ Chowdhry, Wiley (Chichester), 1998 and Pharmaceutical Thermal Analysis, edited by JL Ford and P Timmins, Ellis Harwood, 1989 (although a new edition of this text is due, edited by JL Ford, P Timmins and G Buckton). 

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... 

Figure 8 Structural relaxation times for quench-cooled glassy disaccharides as determined from enthalpy relaxation data. Structural relaxation times were obtained by a fit of the data to the stretched exponential function (see [37,50]). ( ) Data for sucrose obtained by differential scanning calorimetry on annealed samples [37], (O) Data for sucrose obtained by isothermal microcalorimetry [50]. (A) Data for trehalose obtained by isothermal microcalorimetry [50].

Interactions between water vapor and amorphous pharmaceutical solids were evaluated using isothermal microcalorimetry. " The desorption of water from theophylline monohydrate has been investigated using microcalorimetric approaches.The properties of surfactants and surface-active drugs in solution were studied by Attwood et al. " using calorimetry, while titration microcalorimetry has been utilized to elucidate the nature of specific interactions in several pharmaceutical polymer-surfactants systems. " Drug decomposition was evaluated as a function of different... 

Microcalorimetry is an extremely sensitive technique that determines the heat emitted or adsorbed by a sample in a variety of processes. Microcalorimetry can be used to characterize pharmaceutical solids to obtain heats of solution, heats of crystallization, heats of reaction, heats of dilution, and heats of adsorption. Isothermal microcalorimetry has been used to investigate drug-excipient compatibility [82]. Pikal and co-workers have used isothermal microcalorimetry to investigate the enthalpy of relaxation in amorphous material [83]. Isothermal microcalorimetry is useful in determining even small amounts of amorphous content in a sample [84]. Solution calorimetry has also been used to quantitate the crystallinity of a sample [85]. Other aspects of isothermal microcalorimetry may be obtained from a review by Buckton [86]. 

The binding parameters of both hosts with chloride were determined using isothermal titration calorimetry. The microcalorimetry experiments re-... 

Isothermal microcalorimetry is a versatile method that can be used for diverse applications such as assessing chemical stability, heats of dissolution by solution calorimetry, and binding affinities by titration calorimetry. An important application of isothermal microcalorimetry related to characterization of solids is the determination of the amorphous content [9]. Typically, it is desired that the product of a crystallization process is 100% crystalline. If the crystallization process is carried out in a nonoptimized way, the resulting solid may contain amorphous fractions. One possible cause for this could be that the crystallization is carried out too fast. Also, processes following the crystallization process, such as drying or milling, may induce formation of amorphous fractions. In most instances such amorphous fractions are undesired, since they may reduce the chemical stability and change the dissolution characteristics of the product. 

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 addition to conventional techniques used to observe amorphous material, such as DVS and XPRD, isothermal microcalorimetry and solution calorimetry can be used to observe and accurately quantify amorphous materials. 

From Equation (17) an analysis can be made if the quantity of ML can be determined as a function of ligand added at each aliquot. However considerable errors may arise as this quantity must be assayed, after each aliquot of ligand is added. However non-invasive techniques such as isothermal microcalorimetry calorimetry can be used to directly determine the quantity of ML without disturbing the system. For a calorimetric analysis an estimation of the enthalpy change for the macromolecule-ligand interaction must be made. An assumption can be made that at the start of the study, the initial aliquot of ligand added to the system, if sufficiently small, will completely bind to the macromolecule (as initially the macromolecule will be in excess). The enthalpy change associated with this interaction can then be used to calculate the A// for the interaction (Equation (3)). 

The determination of adsorption thermodynamic quantities such as adsorption heats can now be performed through direct or indirect methods with a great degree of accuracy. The foundations of gas—solid interface calorimetry have been well established by combining adsorption microcalorimetry with adsorption in quasi-equilibrium. The experimental results reported so far, obtained from different calorimetries, concur with the values calculated from adsorption isotherms. 

The kinetics of degradation can be studied using isothermal calorimetry, that is, calorimetry performed at constant temperature. Recently, sensitive thermal conductivity microcalorimeters useful for detecting even small amounts of degradation at room temperature have become available. For example, the slow solid-state degradation of cephalosporins at a rate of approximately 1% per year was successfully measured by microcalorimetry.624... 

Despite the great diversity in the design of microcalorimeters and the experimental procedures described in the literature [1-10], only two microcalorimetric methods have found widespread application in cydodextrin (CyD) studies and drug-design research. These two methods are differential scanning calorimetry (DSC) and isothermal titration microcalorimetry (ITC). DSC and ITC can be con-... 

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