A new approach for the estimation of the melting enthalpy of metastable crystalline compounds using differential scanning calorimetry: Application to the two crystallographic forms of Etiracetam

Herman, C.;Leyssens, Tom;Vermylen, V.;Halloin, V.;Haut, B.
(2012) Journal of Thermal Analysis and Calorimetry : an international forum for thermal studies — Vol. 107, n° 2, p. 777-788 (2012)

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Authors
  • Herman, C.ULB
    Author
  • Leyssens, TomUCLouvain
    Author
  • Vermylen, V.UCB
    Author
  • Halloin, V.ULB
    Author
  • Haut, B.ULB
    Author
Abstract
This article focuses on the development of an innovative method, based on thermodynamic considerations and with the use of Differential Scanning Calorimetry (DSC), for the estimation of the melting enthalpy of crystalline compounds which are metastable near their melting temperature. The curves obtained, at various heating rates, are analysed in two steps. In the first step, the area of a zone generated by the melting endothermic peak is calculated following a specific method. In the second step, the melting enthalpy is extracted from this area through an enthalpy balance. This method is applied to both identified crystallographic forms, named form I and form II, respectively, of Etiracetam (UCB Pharma). The results show that the melting enthalpy of the stable form II compare well with the ones obtained using conventional methods. The curves of the metastable form I present thermal instabilities (partial solid-solid polymorphic transition and beta-recrystallization) near the form I melting peak leading to difficulties for a direct determination of the melting enthalpy by conventional methods. The proposed method is therefore very useful for the estimation of the form I melting enthalpy. © Akademiai Kiado, Budapest, Hungary 2011.
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Herman, C., Leyssens, T., Vermylen, V., Halloin, V., & Haut, B. (2012). A new approach for the estimation of the melting enthalpy of metastable crystalline compounds using differential scanning calorimetry: Application to the two crystallographic forms of Etiracetam. Journal of Thermal Analysis and Calorimetry : an international forum for thermal studies, 107(2), 777-788. https://doi.org/10.1007/s10973-011-1555-0 (Original work published 2012)