Inferring thermodynamic stability relationship of polymorphs from melting data

Yu, Lian

doi:10.1002/jps.2600840812

Cited by 264 publications

(153 citation statements)

References 20 publications

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“…23 TGA of TXP form II revealed no weight loss from the samples over the 110±1308C temperature range, indicating that the ®rst endotherm in the DSC trace cannot be attributed to any inclusion of solvent in the crystal. Attempts to record melting of polymorph II by increasing the DSC scanning rate up to 100 K min À1 for possible application of the Heat of Fusion Rule 23,24 were unsuccessful. By stopping a DSC run on TXP form II at 1508C and cooling to 308C, however, a broad exothermic region in the range 105±658C was recorded (see inset of Fig.…”

Section: Thermal Analysis and Ir Spectroscopymentioning

confidence: 99%

Structural relationships, thermal properties, and physicochemical characterization of anhydrous and solvated crystalline forms of tetroxoprim

Caira

Bettinetti

Sorrenti

2002

Journal of Pharmaceutical Sciences

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Section: Thermal Analysis and Ir Spectroscopymentioning

confidence: 99%

Structural relationships, thermal properties, and physicochemical characterization of anhydrous and solvated crystalline forms of tetroxoprim

Caira

Bettinetti

Sorrenti

2002

Journal of Pharmaceutical Sciences

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“…However, enantiotropy was found to exist between polymorphic pair VI L /VI H . The melting point data (30) and heat of solution data (31) can be used to determine the virtual temperature of transition in the polymorphic pairs. But in our study, the melting data method was not used to determine transition temperature because the enthalpy of fusion of lower melting is very small and it seems to overlap with exotherm which depicts the phase-phase transition (Table 1).…”

Section: Estimationmentioning

confidence: 99%

An Insight into Thermodynamic Relationship Between Polymorphic Forms of Efavirenz

Chadha

Arora²,

Saini³

et al. 2012

J Pharm Pharm Sci

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-Purpose:The aim of the work is to study the crystallization of efavirenz to understand the preferential formation of various polymorphic forms, to establish their identity, to study the transformation between the polymorphic forms on heating and to determine their free energy. Methods: Slow crystallization from different solvents under controlled conditions was employed to prepare various crystalline forms. The TGA and DSC were used to study their thermal behavior and inter-conversion of these forms. The calorimetrically determined enthalpies of solution and solubility data are utilized to determine the transition temperatures. Results: Six polymorphic forms of efavirenz are identified and characterized completely. The TGA scans of all the forms did not show any mass loss indicating absence of hydrate or solvate. The thermally induced transformations are observed in the DSC scans of five forms II-VI indicating them to be metastable which are converted to stable higher melting forms. The melting temperature and enthalpy of fusion of lower melting (Form L ) and higher melting forms (Form H ) reveal that four of these polymorphic pairs are monotropically related. The enthalpies of solution of Form L are found to be more exothermic as compared to corresponding Form H . The transition temperature (T t ) determined using enthalpy of solution and solubility data was found to be higher than the melting of both the forms except for polymorphic pair VI L /VI H . The effect of ΔC p on transition temperature is also reported. Conclusions: The form I is found to be thermodymanically most stable but least soluble. The forms II-V are metastable and are converted irreversibly to stable forms. The enthalpy of fusion rule and virtual transition temperature provided complementary evidence for the existence of monotropy in these polymorphic pairs. However, enantiotropy is demonstrated in VI L /VL H pair and is well established in our study. Novelty: The present study reveals the thermodynamic aspects of various isolated polymorphic forms of efavirenz. Solution calorimetry along with other techniques is used to study the transformation of one form to another. The emphasis is laid on determination of transition temperature of various polymorphic pairs which has not been reported earlier.

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“…In these cases the difference in the entropies of fusion are more meaningful to distinguish between monotropism and enantiotropism than the difference in the heats of fusion. [31][32][33][34] Because the melting points of D-mannitol mod. I and mod.…”

Section: -32mentioning

confidence: 99%

Energy/Temperature Diagram and Compression Behavior of the Polymorphs of d-Mannitol

Burger

Henck

Hetz

et al. 2000

Journal of Pharmaceutical Sciences

323

230

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Inferring thermodynamic stability relationship of polymorphs from melting data

Cited by 264 publications

References 20 publications

Structural relationships, thermal properties, and physicochemical characterization of anhydrous and solvated crystalline forms of tetroxoprim

Structural relationships, thermal properties, and physicochemical characterization of anhydrous and solvated crystalline forms of tetroxoprim

An Insight into Thermodynamic Relationship Between Polymorphic Forms of Efavirenz

Energy/Temperature Diagram and Compression Behavior of the Polymorphs of d-Mannitol

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