Abstract
In this work, the solubility of a non-steroidal anti-inflammatory drug (NSAID), piroxicam, is investigated. The polymorphic form II, which is the most stable form at room temperature, was investigated in seven different solvents with various polarities. It has been found that the solubility of piroxicam in the solvents is in the following order: chloroform > dichloromethane > acetone > ethyl acetate > acetonitrile > acetic acid > methanol > hexane. Crystallization of piroxicam from different solvents has been performed with evaporative crystallization and cooling crystallization; the effects of solvent evaporation rate and solute concentration have also been studied. Both form I and form II could be produced in cooling and evaporative crystallization, and no simple link can be identified between the operating parameters and the polymorphic outcome. Results obtained in the present work showed the stochastic nature of the nucleation of different polymorphs as well as the complexity of the crystallization of a polymorphic system.
Highlights
Crystallization often serves as the final separation and purification step in the production of active pharmaceutical ingredients (APIs) [1]
Crystallization of piroxicam from different solvents has been performed with evaporative crystallization and cooling crystallization; the effects of solvent evaporation rate and solute concentration have been studied
The solubility of piroxicam form II measured in the seven solvents, including dichloromethane, chloroform, ethyl acetate, acetonitrile, acetic acid, methanol and hexane are shown in Table 1 and Figure 1a,b
Summary
Crystallization often serves as the final separation and purification step in the production of active pharmaceutical ingredients (APIs) [1]. Other process parameters should be considered as these will influence the polymorphic form It was observed in our previous study that the formation of INA polymorphs depended on the solute concentration as well as the temperature at which nucleation was onset [7,8]. It was observed that both form I (BIYSEH01, 03, 04, 10, 13, 14, 16) and form II (BIYSEH02, 08) of piroxicam could be yielded; the frequency of occurrence of the polymorphs did not show any clear dependence on the characteristics of the solvents and the other operating parameters This is in agreement with recently published literature [15] in which the stochastic nucleation of INA polymorphs was demonstrated by both experimental and modeling approaches. A Bruker Senterra Dispersive Raman microscope (Bruker, Billerica, MA, USA) with a 785 nm laser operating at 100 mW with a 5 s integration time and two scans was used to collect the spectra
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