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The purpose of the present study was to harmonize the protocol of equilibrium solubility measurements for poorly water-soluble drugs to lower inter-laboratory variance. The “mandatory” and “recommended” procedures for the shake-flask method were harmonized based on the knowledge and experiences of each company and information from the literature. The solubility of model drugs was measured by the harmonized protocol (HP) and the non-harmonized proprietary protocol of each company (nonHP). Albendazole, griseofulvin, dipyridamole, and glibenclamide were used as model drugs. When using the nonHP, the solubility values showed large inter-laboratory variance. In contrast, inter-laboratory variance was markedly reduced when using the HP.

The preparation of cinchonidine (CCND) nanocrystals and their immobilization onto the inner surface of a fused silica capillary was investigated for use in the enantioseparation by capillary electrochromatography. The CCND nanocrystals were prepared by an emulsion method that utilizes crystal growth in an oil-in-water emulsion without a stabilizer. As a result, white-colored aqueous dispersions of organic nanoparticles were obtained. SEM images showed that the prepared CCND nanocrystals were from 300 to 700 nm in size. When the obtained dispersion was introduced into a poly(diallyldimethylammonium chloride) (PDDAC) coated capillary, the nanocrystals were strongly adsorbed onto the inner surface due to an electrostatic interaction between cationic PDDAC and the negatively charged organic nanocrystals. In CCND nanocrystals coated capillary, CEC enantioseparations of racemic amino acids were successfully achieved. The reproducibilities of the detection times were acceptable with a relative standard deviation of less than 7%, indicating that stable nanocrystal coating could be obtained by our proposed method.