Studies on Aspirin Crystals Generated by a Modified Vapor Diffusion Method

Abstract

Abstract. The objectives of the current investigation were (1) to study the influence of selected two different non-solvents (diethylether and dichloromethane) on the drug crystal formation of a model drug, aspirin (ASP-I) by the modified vapor diffusion method and (2) to characterize and compare the generated crystals (ASP-II and ASP-III) using different analytical techniques with that of unprocessed ASP-I. When compared to the classical vapor diffusion method which consumes about 15 days to generate drug crystals, the modified method needs only 12 h to get the same. Fourier transform-infrared spectroscopy (FT-IR) reveals that the internal structures of ASP-II and ASP-III crystals were identical when compared with ASP-I. Although the drug crystals showed a close similarity in X-ray diffraction patterns, the difference in the relative intensities of some of the diffraction peaks (especially at 2θ values of around 7.7 and 15.5) could be attributed to the crystal habit or crystal size modification. Similarly, the differential scanning calorimetry (DSC) study speculates that only the crystal habit modifications might occur but without involving any change in internal structure of the generated drug polymorphic form I. This is further substantiated from the scanning electron microscopy (SEM) pictures that indicated the formation of platy shape for the ASP-II crystals and needle shape for the ASP-III crystals. In addition, the observed slow dissolution of ASP crystals should indicate polymorph form I formation. Thus, the modified vapor diffusion method could routinely be used to screen and legally secure all possible forms of other drug entities too.

Solubility Study of Acetylsalicylic Acid in Ethanol + Water Mixtures: Measurement, Mathematical Modeling, and Stability Discussion

“…It has been reported that the significant difference in the enthalpy could be due to changes in the crystallinity of acetylsalicylic acid after the solubility test. This has been shown when acetylsalicylic acid has been crystallized from various organic solvents ( 53 ). The enthalpy data in Table II shows that the acetylsalicylic acid crystals filtered after the solubility test in 100% water have less crystallinity compared to untreated acetylsalicylic acid.…”

Synthesis and Antimicrobial Activity of 2-Trifluoroacetonylbenzoxazole Ligands and Their Metal Complexes

“…Such increased activity of the metal complexes can be explained on the basis of Overtone concept and Tweedy chelation theory. 56,57) According to the overtone concept of cell permeability, the lipid membrane that surrounds the cell favors the passage of only lipid-soluble materials; therefore, lipophilicity is an important factor which controls the antibacterial activity. On chelation, polarity of the metal ion is reduced to a greater extent due to the overlapping of ligand orbital and partial sharing of the positive charge of the metal ion with donor groups.…”

Understanding Crystal Cleavability and Physical Properties of Crystal Surfaces Using <i>in Silico</i> Simulation

“…Therefore, when the molecules on the crystal plane are peeled off by cleavage, the number of stacked crystal planes and the peak intensity are reduced. 29) It is also shown that the XRD peak of the ground sample is lower than that of the unground sample. In other words, it is reported that the peak area of PXRD is reduced when the number of stuck crystal facets is reduced by grinding.…”

“…In other words, it is reported that the peak area of PXRD is reduced when the number of stuck crystal facets is reduced by grinding. 29) The (1 0 0) and (0 0 2) peak of PXRD were integrated and the peak areas were obtained. Moreover, the total integrated value of each PXRD was calculated.…”