Homochiral porous organic cage used as stationary phase for open tubular capillary electrochromatography

Abstract

Porous organic molecular cages, as a new type of porous materials, have in recent years attracted a tremendous amount of attention for their potential applications. However, to the best of our knowledge, there has been no attempt to utilize porous organic molecular cages as stationary phases in capillary electrochromatography (CEC). We report herein the use of a homochiral porous organic cage (POC) (CC3-R) as a stationary phase in open tubular capillary electrochromatography (OT-CEC) for the separation of chiral compounds and positional isomers. The column was fabricated using CC3-R as the stationary phase by a static coating method. Separation of furoin, benzoin, and alprenlol were achieved on the CC3-R coated column, with the highest resolution value (Rs = 3.35) for the separation of benzoin. The influences of pH and buffer concentration on separation have been investigated. Besides, the CC3-R column also exhibited good selectivity for the separation of positional isomers, including those of nitrophenols, phenylenediamines, aminophenols, and ionones. The run-to-run (n = 5), day-to-day (n = 5), column-to-column (n = 3), and batch-to-batch (n = 3) relative standard deviations (RSDs) for the analyte migration time were in the range of 0.5–1.5%, 0.2–1.8%, 1.2–2.1% and 1.5–2.8%, respectively. The RSDs for the migration time and enantioselectivity of the analyte were less than 5.9% and 2.2% (inter-day, n = 5) after a week of continuous use. This work also indicates that porous organic molecular materials are promising for enantioseparation in CEC and look set to become more attractive in separation science.