In a previous study, the amount of adsorbed quinine chloride was measured using a bitterness sensor and peaks were observed in the lipid concentration and the amount of adsorbed quinine chloride [72]. In addition, the CPA value saturated for an amount of adsorbed quinine chloride of 3 μg/cm2 or more. Therefore, quinine chloride and iso-α acid show similar adsorption behaviors. This fundamental finding on the CPA value will contribute to the development of new lipid/polymer membranes and the further improvement of global selectivity.