Thermodynamic Solubility Assays

• Thermodynamic solubility tests evaluate the solubility of solid crystalline material in aqueous solvent as a saturated solution in equilibrium
• Thermodynamic aqueous solubility tests can be performed in any media or buffer

Kinetic Solubility Assays

• Aqueous kinetic solubility tests evaluate the solubility of a compound already fully dissolved in an organic solvent
• Kinetic solubility tests can be performed in any media or buffer

Fasted State Simulated Gastric Fluid (FaSSGF) pH 1.6 Solubility

• Solubility assay performed in artificial FaSSGF
• This biologically relevant fluid mimics gastric juices because it contains natural surfactants (salts and acids)

Fasted (FaSSIF) and Fed State Simulated Intestinal Fluid (FeSSIF) pH 6.5 Solubility Assays

• Solubility assay performed in artificial FaSSIF/FeSSIF
• This biologically relevant fluid mimics intestinal juice because it contains natural surfactants (bile salts and lecithin)

Partition Coefficient (Log D) Assays

• Log D coefficient is the ratio of concentrations of a compound in the two phases of a mixture of two immiscible solvents at equilibrium
• This method involves dissolving the compound in a known volume of octanol (hydrophobic) and water or PBS (hydrophilic)
• Shake-flask method