A kinetic study of polymorphic transition of anhydrous caffeine with microcalorimeter

Miniaturized Assay for Solubility and Residual Solid Screening (SORESOS) in Early Drug Development

“…In DSC, CAF form II showed a shallow endothermic peak at 141.4-C (onset temperature) and a sharp endothermic peak at 235.7-C (data not shown). The first endotherm was related to the reported enantiotropic transition of CAF form II to the high-temperature form and the second endotherm to the subsequent melting of form I (20). The formation of CAF modification I after heat treatment of form II (180-C for 16 h) was confirmed by standard XRPD analysis (Fig.…”

“…The residual solids were subsequently dried on filter paper at room temperature for 30 min. The high temperature form I of CAF was prepared by heating the commercial CAF (form II) at 180-C for 16 h in a closed vessel (20).…”

“…CAF exists as two anhydrous crystal forms (I, II) and one crystalline nonstoichiometric hydrate with 0.8 moles of water per mole of CAF (29,30). Form II of CAF, which is the stable polymorph at ambient conditions converts to form I at high temperature (20).…”

Thermochemical study of two anhydrous polymorphs of caffeine

“…The pellets for the combustion experiments were made quickly and kept, under inert atmosphere, inside a refrigerator (5°C) for a maximum period of 24 h. Due to its metastability, at room temperature, the process was repeated whenever necessary, for example, if a systematic tendency in the specific energy of combustion was observed on successive combustion runs. Although, Epple et al [12] and Descamps and coworkers [10,13], based on time-and temperature-resolved X-ray powder diffraction, and kinetic studies made by Lehto and Laine [14] by using isothermal microcalorimetry, confirm that, at room temperature, the conversion form I ! form II is very slow.…”

Insights into phase stability of anhydrous/hydrate systems: a Raman‐based methodology

“…[40,52,54 -58] The anhydrous β-form, hereafter named as CAa (anhydrous CA), is stable at room temperature, whereas the α-form only occurs at higher temperatures. [44,45,56,59] The present paper has been organized as follows. Firstly, the methodology applied is described.…”