Investigation of thermodynamic properties of ascorbic acid crystal in different solvents using experimental and simulations methods
Crystal chemistry is identified as an important key factor to be explored in relation to the thermodynamic of crystallization solution to lead the formation of active pharmaceutical ingredient (API) crystals. In this study, solubility of ascorbic acid was determined by gravimetric method in four dif...
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| Format: | Thesis |
| Language: | English |
| Published: |
2019
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| Subjects: | |
| Online Access: | http://umpir.ump.edu.my/id/eprint/29307/1/Investigation%20of%20thermodynamic%20properties%20of%20ascorbic%20acid%20crystal%20in%20different%20solvents%20using%20experimental%20and%20simulations%20methods.wm.pdf |
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| Summary: | Crystal chemistry is identified as an important key factor to be explored in relation to the thermodynamic of crystallization solution to lead the formation of active pharmaceutical ingredient (API) crystals. In this study, solubility of ascorbic acid was determined by gravimetric method in four different polar protic solvents; water, methanol, ethanol and 2-propanol. It shows that ascorbic acid is highly soluble in high polar molecule (water) and the solubility was decreased with the reduction of solvent polarity (methanol > ethanol> 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 Gibbs free energy (ΔG) values is based on the solubility that were experimentally obtained to simulate main intermolecular forces like hydrogen bond, Van der Waals forces and electrostatic forces. Hydrogen bond forces is found to be stronger compared to other intermolecular forces which give directionality to crystal formation. The other thermodynamic properties of ascorbic acid in different solvents was analysed using van’t Hoff plot. Crystallization is likely to occur at a more thermodynamically favorable condition in ΔG is low. This thermochemistry information provides an insight on the relationship between the crystal habit and its habit across four different polar protic solvents. The habit of crystal was then observed and its crystal quality was characterized by powder X-ray diffraction (PXRD), single x-ray diffraction (SCXRD), light microscopy and scanning electron microscopy techniques. The thermal properties of the crystals were studied using results from thermal gravimetric analysis (TGA) and differential scanning calorimeter (DSC). The results showed that high polarity solvents formed stronger intermolecular forces during dissolution hence influence the solubility of ascorbic acid. Strong intermolecular forces are also observed to help to give directionality during crystallization process. Strong polarity and stronger hydrogen bond propensity solvent tend to form equidimensional crystal like prism while weaker polarity solvent showed smaller crystal formation. Solvent polarity changes the habit of ascorbic acid crystal but did form a new polymorph. |
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