Solubility of Paracetamol and Polyvinylpyrrolidone in Mixtures of Carbon Dioxide, Ethanol, and Acetone at Elevated Pressures

The solubilities of two solutes, paracetamol (PCM) and polyvinylpyrrolidone (PVP), are presented in mixtures of carbon dioxide (CO2), acetone, and ethanol at a temperature of 313 K and at elevated pressures between 10 MPa and 16 MPa. The solubilities of the solutes have been quantified in terms of the solute molar fraction as a function of the composition of the mixture of CO2/acetone/ethanol. The composition of the mixture has been quantified in terms of the CO2 molar fraction in the range of 0.46 < x(CO2)< 0.94. As well, the solubilities of mixtures of both solutes have been measured to determine the solubility behavior when paracetamol and polyvinylpyrrolidone are both present. The saturation solubilities of the solutes have been determined visually, observing the transition of a supersaturated multiphase system to a saturated single-phase system in a variable-volume high-pressure view cell. As an indicator for this transition the "vanishing cloud point" has been used. The obtained solubilities show that CO2 acts as an antisolvent and that the solubilities increase with increasing pressure. Furthermore it is shown that PVP is significantly less soluble than PCM. The solubilities of both solutes decrease with increasing content of acetone in the mixture. The influence of the PVP molecular weight (40 kg center dot mol(-1) and 1300 kg center dot mol(-1)) on the solubilities has been analyzed, observing that the solubilities of PVP in terms of molar fractions decrease with increasing molecular weight. For the case of both solutes being present in the mixture it could be shown that the presence of the sparingly soluble PVP does not significantly influence the solubility of the slightly soluble PCM, while the presence of the slightly soluble PCM significantly influences the solubility of the sparingly soluble PVP.