Evaluation of solvents’ effect on solubility, intermolecular interaction energies and habit of ascorbic acid crystals

Solubility of active pharmaceutical ingredient (API) in solvents is very important for drug development and manufacturing. Solubility data may provide further information such as thermochemical properties and intermolecular interactions that may lead to a better understanding of the formation of API crystals. In this study, solubility of ascorbic acid was determined by gravimetric method in four different commonly used polar protic solvents: water, methanol, ethanol and 2-propanol. The solubility of ascorbic acid crystal was also predicted using Conductor-like Screening Model – Realistic Solvent (COSMO-RS) approach. In this computational analysis, the generated ΔG values are based on the solubilities that were experimentally obtained to simulate the intermolecular forces. The intermolecular interaction data from COSMO-RS provide an insight into the relationship between the intermolecular interactions and its crystal habit across four different polar protic solvents. The habit of the crystals was then determined using light microscopy and scanning electron microscopy techniques, while the polymorphic form of the crystals was identified by X-ray powder diffraction and single X-ray diffraction techniques. The solubility and characterization data showed that the solvents with high polarity increased the solubility of ascorbic acid. The data also showed that different solvent polarity influenced the crystal habit, but did not change the crystal structure to form a new polymorph. Keywords: Solubility, Intermolecular forces, Crystal habit, COSMO-R

The effect of particle size on physicochemical and thermal analysis of rice husk for explosion studies

The effect of rice husk particle size on physicochemical and thermal behaviour was studied for identify whether it has the potential to explode. The thermal degradation of the lignocellulosic constituent in rice husk was evaluated via thermogravimetric analysis (TGA). Rice husk morphology and elemental composition were evaluated via scanning electron microscopy with energy dispersive X-ray (SEM-EDX). Results showed that the rice husk samples were richer in cellulose than in lignin in terms of weight percent, indicating that they were combustible. Uncontrolled combustion propagation can lead to an explosion. However, the presence of ±5 wt% silicon in rice husk may reduce the explosion severity due to its low thermal conductivity. Furthermore, the smallest particle size, 71 μm recorded faster thermal degradation and more explosive as compared to 106, 160 and 250 μm. This preliminary data is very useful to improve the safety technique specifically for rice husk dust explosion protection, prevention, and mitigation