Determination and Correlation of the Solubility for Berberine Chloride in Pure Imidazolium-Based Ionic Liquids

The solubility of berberine chloride in several imidazolium-based ionic liquids (ILs), that is, [Rmim]BF4, [Rmim]NO3, [Rmim]PF6, and [Rmim]NTf2 (R = butyl, hexyl, and octyl), were measured using a laser monitoring observation method from 299.45 to 364.35 K at atmospheric pressure. The solubility of berberine chloride in selected ionic liquids increased as the temperature increased and is dominantly dependent on the type of IL's anion structure with the trend of NTf2- >> NO3- > PF6- > BF4-. The ILs with NTf2- anion exhibited good dissolubility to berberine chloride, especially at high temperature. The correlated solubility data via Apelblat equation is in better agreement with the experiment solubility compared to Dual parameter equation and Ah equation.