Abstract
Mefenamic acid [2-(2, 3-dimethylphenyl) amino benzoic acid] is an active pharmaceutical compound that exist in different polymorphic form and shape. In this work the effect of solvents on polymorphism and shape of mefenamic acid crystals were examined. The solvents used were ethanol, isopropanol, ethyl acetate, dimethyl acetamide, dimethyl formamide, and acetone. Natural cooling was employed during the crystallisation process. The crystals produced were dried and analysed using optical microscopy, differential scanning calorimetry, thermal gravimetric analysis, x-ray powder diffraction (XRPD) and fourier transform infrared spectroscopy (FTIR). The analysis confirmed that the crystals obtained using ethyl acetate, ethanol, isopropanol, and acetone are pure Form I with a needle-like flat shape. Meanwhile, the crystallisation using DMF produced polymorphic Form II in cubic shape.
Highlights
Solvent demonstrate an important role in the crystallisation process as it can contribute to the polymorphic selectivity of targeted pharmaceutical compound [1, 2]
The solvent-solute interactions, i.e. hydrogen bonding have been proven to affect the birth of different polymorphic forms [3]
A comparison, cannot be made for crystals obtained using dimethyl acetamide (DMA) as it is yet to be reported in the literature
Summary
Solvent demonstrate an important role in the crystallisation process as it can contribute to the polymorphic selectivity of targeted pharmaceutical compound [1, 2]. This is because, at the molecular level, the solvent can selectively adsorb onto the crystals faces or interact with the solute clusters. The solvent-solute interactions, i.e. hydrogen bonding have been proven to affect the birth of different polymorphic forms [3]. Crystallisation of sulfathiazole using water produces polymorphic Form II and III. The polymorphic Forms I and IV are obtained from acetone, while npropanol gives only Form I [5]
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