Study of Different Crystal Habits of Aprepitant: Dissolution and Material Attributes

In the present study, aprepitant (APT) was selected to find its suitable crystal habit, which can improve its existing poor dissolution and manufacturing processability. Solvents were screened out for solubility analysis of APT and further crystal habit modification. Solid-state characterization studies like powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier infrared spectroscopy (FTIR) distinguished that tabular crystal habit was generated from acetone (APT-AC) and long tabular crystal habit was generated from ethyl acetate (APT-EA). Kawakita analysis and powder flow property studies showed that APT-EA is cohesive, has poor flow property and low bulk density compared to APT-AC (p < 0.05). Heckel plots reflected that APT-EA shows higher fragmentation and particle rearrangement during the initial stages as indicated by the higher intercept values. Higher slopes in APT-EA and APT-AC confirmed better plasticity but lower yield pressure in APT-AC proved good plastic deformation compared to APT-EA (p < 0.05). The dissolution profile of the APT-EA was found to be better than that of APT-AC. Overall, it can be concluded that APT-AC crystal habit has a better flow rate, tensile strength, and plasticity whereas APT-EA has better dissolution.

Structural study of cadmium hydroxide sulfates. VI. The layer structure of Cd4SO4(OH)6.1.5H2O studied from X-ray powder and single-crystal diffraction data

The crystal structure of the layered cadmium hydroxide sulfate Cd4SO4(OH)6.1.5H2O has been solved from X-ray powder diffraction data. The compound crystallizes with hexagonal symmetry, a=9.145(1) Å, c=15.099(3) Å, V=1093.5 Å3, Z=4, space group P63. Due to the unusual environment of one cadmium atom and to the fact that a suitable thin tabular crystal could be found later, a single-crystal X-ray diffraction experiment was also carried out. In both cases the structure was solved applying direct-methods. The refinements converged to the residual factors Rwp=0.152 and RF=0.059 from the powder data and R1=0.058 and wR=0.165 for the single crystal data case. The structure is built from brucite-type layers based on CdO6 octahedra, in which one-seventh of the octahedral sites are empty. Directly above and below these empty sites, two additional octahedrically coordinated Cd atoms are located. The crystal chemistry of the cadmium hydroxide sulfate family is discussed.

Astrophyllite from Kangerdlugssuaq, East Greenland

Astrophyllite has been found in alkalic pegmatite dykes on the two sides of Kangerdlugssuaq fjord. At the eastern locality, Kraemers Island, the dyke is silica oversaturated and the astrophyllite occurs in a broad tabular crystal habit. The dyke at the western locality, Bagnaesset, is silica undersaturated and the astrophyllite occurs in elongated prisms of acicular habit. Electron probe analyses of the crystals of the two habits have shown systematic chemical differences which not only relate to Mn and Ti compositional variations, but also reveal departures from ideal stoichiometry in varying degrees. Based on this latter feature a model involving polysomatism has been constructed which may explain the differences in crystal habit.