Study on solubility of pharmaceutical compounds in ionic liquids

Dissertation to obtain the degree of master in Chemical and Biochemical Engineering

The sufficient solubility of N-acetyl-L-cysteine (NAC), coumarin (COU) and 4-hydroxycoumarin (4HC) in alternative solvents obtained in this work can open new perspectives in pharmaceutical processing. Solid–liquid equilibrium (SLE) measurements have been made using a dynamic (synthetic) method. The melting point and the enthalpy of fusion of the pharmaceutical compounds were acquired using differential scanning calorimetry (DSC). The solubility of N-acetyl-L-cysteine and 4-hydroxycoumarin in trifluoromethanesulfonate ionic liquids was found to be significantly higher than in the studied bis(trifluoromethylsulfonyl)imide ionic liquids, and when compared, coumarin have the opposite behaviour. The best solvent amongst studied for this antioxidant (NAC) and anticoagulants (COU and 4HC) was discovered. The solid–liquid phase equilibrium were described using six different correlation equations which revealed relatively good description with the acceptable standard deviation temperature range. Moreover, the solubility data was used to calculate the 1-octanol/water partition coefficients and experimental partition coefficients (logP) was found to be negative in N-acetyl-L-cysteine and positive in the case of coumarin, at five temperatures with N-acetyl-L-cysteine being more hydrophilic and coumarin more hydrophobic; These results are also proof of the possibility of using these compounds as pharmaceutical products.