Measurement of solubility curves for crystallization processes

Abstract

Solubility data plays a crucial role in the chemical and biological field. Measurement of drug solubility in various solvents is one of the key elements of compound characterization during the whole discovery and development process [1]. It enables engineers to design and optimize crystallization processes, especially in the pharmaceutical field, where a narrow crystal size distribution of the product is an essential specification. For this project, the turbidimetric and direct UV absorption methods were employed to measure the aqueous solubility of artemisinin and paracetamol. The reliability of the turbidity meter in determining the solubility data of poorly soluble drugs like artemisinin could not be justified as the results were unsatisfactory despite significant attempts to troubleshoot the errors. The UV absorption method was explored. A comparison between solubility results of paracetamol obtained from the 2 methods was made. Both methods proved to be fairly reliable with a percentage error between experimental and literature solubility curve within ± 6%. Lastly, the UV calibration curve of artemisinin was determined. Artemisinin was found to have a λmax value of 260 nm, which corresponds with literature [2]. However, the solubility concentrations could not be found as it was uncharacteristically beyond the range of calibration.