Crystallization is used as a purification process in majority of the industries such as pharmaceuticals, food products, chemicals, catalysts, and cosmetics. Crystallization of active pharmaceutical ingredients is carried out to increase the dissolution rate and attain sufficient bioavailability in pharmaceutical industries. It can also enhance the flow properties and drug dosage control of the active pharmaceutical ingredients.
Single crystals give us a lucid understanding of the intrinsic properties of a material. A material made up of many crystals will have grain boundaries which do not allow us to measure properties such as thermal and electrical resistance effectively. Single crystals will not have defects or impurities in them. Thus, help us in making comparisons with other materials and contribute to a better understanding of particular behaviors. Therefore, it is important to investigate the growth of single crystals.
Sulphanilamide is a sulpha class drug used as an intermediate and starting material for the production of various drugs. It is an antibacterial agent and is often used in pharmaceutics and cosmetics. In this study, we wanted to obtain sulphanilamide crystals by two different crystallization methods and compare the results gathered. Sulphanilamide usually crystallizes in the form of needles, thus is ideal for the purpose of this study. In this work, crystallization of sulphanilamide was carried out by cooling method and solvent evaporation method. In Cooling method as temperature was brought down the crystals separated out. On the other hand, in solvent evaporation method, the solvent evaporated leaving behind the crystals. The process parameters that varied included stirring rate of the solution at a constant temperature, concentration of the solute in a constant volume of solvent, solvent systems chosen-acetone, methanol and ethanol, and time allowed for crystallization.
Crystals were obtained under the varying conditions. Characterization of the crystals formed was carried out using X-ray diffraction method, scanning electron microscopy, and differential scanning calorimetry. The size and morphology of the crystals formed was observed and the results were compared. It was found that the crystals obtained from using methanol as solvent, with high concentration of solute, gave the most uniform and large-sized cubic crystals under solvent evaporation method. The surface of the crystal was also seen to be smooth with well-defined edges as shown in the SEM images. Stirring reduced the size of crystals formed, and longer time of crystal formation resulted in larger crystals. Solvent evaporation method gave more uniform crystals compared to cooling method.
This study gives us an understanding of how each parameter affects crystal growth. Thus, optimum conditions for crystal growth can be determined.