Abstract
In this work, the preformulation study on the solid state characterization for the anhydrous form and the monohydrate form of l-phenylalanine has been initially conducted by the use of powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and microscopy. Meanwhile, the solubility of both forms and the transformation kinetics from anhydrous form to monohydrate form in different water/acetone mixtures were studied as well. The transformation rate can be prohibited by increasing temperature and reducing water content in the solvent mixtures. These results will contribute to a better understanding of drugs’ pseudopolymorphism for pharmaceutical industry. Key words: Crystallization, l-phenylalanine, polymorphism, identification, transformation.
Highlights
Pseudopolymorphism refers to the crystalline forms of a compound in which solvent molecules are included as an integral part of the structure (Pedireddi and PrakashaReddy, 2003)
The preformulation study on the solid state characterization for the anhydrous form and the monohydrate form of L-phenylalanine has been initially conducted by the use of powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and microscopy
The monohydrate form of L-phenylalanine was obtained by recrystallization method described as follows: A saturated solution of anhydrate was prepared at 70°C and quenched in a thermostat maintained at 5°C
Summary
Pseudopolymorphism refers to the crystalline forms of a compound in which solvent molecules are included as an integral part of the structure (Pedireddi and PrakashaReddy, 2003). The propensity of a compound to form pseudopolymorphs is deemed to be relevant to molecular structures, hydrogen bonding ability and crystal packing (Khankari and Grant, 1995; Bingham et al, 2001; Infantes and Motherwell, 2002; Gillon et al, 2003). The water molecule, because of its small size, activity and ability to act as both a hydrogen bond donor and acceptor, is found to be more capable of linking to drug molecules to form new crystal structures than any other solvent. It is found that approximately onethird of active pharmaceutical ingredients (APIs) can form crystalline hydrates (Stahl, 1980; Giron et al, 2002)
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