Solubility Definitions

Solubility is expressed in units of concentration. After reviewing  many publications  featuring solubility measurement of drugs we adopted the following definitions for the solubility parameters that our instruments measure.

  • Intrinsic solubility is the equilibrium solubility of the free acid or free base form of an ionisable compound at a pH where it is fully un-ionised.
  • Equilibrium solubility is the concentration of compound in a saturated solution when excess solid is present, and solution and solid are at equilibrium.
  • Kinetic Solubility is the concentration of a compound in solution when an induced precipitate first appears.
  • Supersaturated solutions contain excess neutral species in solution, which will carry on precipitating until the system reaches equilibrium.