Simon Gaisford - Articles and news items

Isothermal calorimetry in the pharmaceutical sciences

Isothermal calorimetry in the pharmaceutical sciences

Issue 3 2013, Thermal Processing / 13 June 2013 / Anthony E. Beezer and Simon Gaisford, UCL School of Pharmacy

Fifty years ago, isothermal microcalorimetry (IMC) was a means to determine thermodynamic data (principally values for enthalpies of formation or reaction to assist in the calculation of Gibb’s Free Energy functions and entropies). These data were used in the compilation of tables of thermodynamic values, for use in evaluating, inter alia, reaction feasibilities, reaction extents (effectively equilibrium constants) and, indeed, reaction enthalpies. For these measurements, an experimental timescale of 30 minutes was considered long. The applications of IMC have developed and expanded considerably over the years, to the point where it can be considered a real-time process monitor with application to virtually all areas of pharmaceutical development. Accompanying this evolution has been a significant growth in the availability of commercial instruments (in contrast to the previous practice of individual, laboratory designed and built instruments).

Fast-scan differential scanning calorimetry

Issue 4 2008, Past issues / 2 August 2008 /

Differential scanning calorimetry (DSC) is a widely used technique within the pharmaceutical industry because the range of phase transitions it can measure usually allows near complete physical characterisation of a new active principal early during preformulation. In addition, because DSC measures a property change that is ubiquitous† (heat) there are very few samples that cannot be investigated.

Calorimetry for polymorph detection

Issue 2 2007, Past issues / 27 March 2007 / Simon Gaisford PhD., School of Pharmacy, University of London and Michael AA O’Neill PhD., Department of Pharmacy and Pharmacology, University of Bath

Characterising the properties of a material, understanding how these properties change in relation to local environment and quantifying potential interactions with other species are facets central to any drug development programme. Not understanding and, more importantly, not controlling these factors can have serious consequences for a pharmaceutical, from irreproducible processing to poor bioavailability, product instability and, worse, patentability. Properties that may be characterised include solubility, dissolution rate, stability (in combination with other excipients and as a function of relative humidity and temperature) and per cent crystallinity (or amorphous content).


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