Abstract
It is well known that the implementation of the conventional model-fitting (CMF) method leads to several indistinguishable ‘best’ candidate models (BCMs) for a single-step isothermal solid-state reaction (ISSR), meaning that subjective selection becomes unavoidable. Here, we developed a more robust comprehensive model-fitting method (COMF) which, while maintaining the mathematical simplicity of CMF, utilizes a ranking criterion that enables automatic and unambiguous determination of the BCM. For each model evaluated, COMF, like CMF, fits the integral reaction rate, but, unlike CMF, it also fits the experimental conversion fraction and reaction speed. From this, three different determination coefficients are calculated and combined to rank the considered models. To validate COMF, we used two sets of experimental kinetic data from the literature regarding the isothermal desolvation of pharmaceutical solvates: (i) tetrahydrofuran solvates of sulfameter, and (ii) methanol solvates of ciclesonide. Our results suggest that from an algorithmic perspective, COMF could become the model-fitting method of choice for ISSRs making the selection of BCM easier and more reliable.
Highlights
Solid-state reactions (SSRs) induced by heating occur in a broad range of processes such as the desolvation and dehydration of pharmaceutical crystals [1,2,3,4,5,6,7,8] or thermal decomposition of solids, e.g., pyrolysis [9,10,11,12,13]
comprehensive model-fitting method (COMF) on two sets of experimental kinetic data from the literature regarding the isothermal desolvation of pharmaceutical solvates: (i) tetrahydrofuran solvates of sulfameter [4] and (ii) methanol solvates of ciclesonide [3]
We validated COMF on two sets of experimental kinetic data from the literature regarding the isothermal desolvation of pharmaceutical solvates: (i) tetrahydrofuran solvates of sulfameter [4]; and (ii) methanol solvates of ciclesonide [3]
Summary
Solid-state reactions (SSRs) induced by heating occur in a broad range of processes such as the desolvation and dehydration of pharmaceutical crystals [1,2,3,4,5,6,7,8] or thermal decomposition of solids, e.g., pyrolysis [9,10,11,12,13]. We are interested in using CMF for analyzing single-step isothermal solid-state reactions (ISSRs) [22], which usually take place during the drying process of pharmaceutical hydrates/solvates [1,2,3,4,21,23,24,25,26]. ISSR and the complete kinetic triplet is calculated This is done by fitting the integral reaction rate of each model explored with a straight line. We improve CMF by developing a more robust comprehensive model-fitting method (COMF) for the case of single-step ISSRs. Our method maintains the mathematical simplicity of CMF, while it utilizes an alternative ranking criterion that enables automatic and unambiguous determination of the BCM.
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