Memory effect of diethylamine mobile phase additive on chiral separations on polysaccharide stationary phases.

The existence of a memory effect for amine additives on polysaccharide chiral stationary phases has often been suggested, but not clearly demonstrated. Demonstration of this effect is made difficult by the uncertainty as to which analytes benefit from use of amine additives and, typically, an unclear history of column use. In this work, analytes were selected for differences in their behavior with and without additives. Columns were used with no prior history. A persistent memory effect was demonstrated on a CHIRALPAK AD-H column in hexane-based mobile phases. This effect was short-lived, with polar organic mobile phases. Memory was short-lived on a CHIRALCEL OJ-H column. Flushing with isopropanol was shown to remove most of the memory effect. Compounds expected to require amine additives on CHIRALCEL OD-H column did not. Acid treatment of the AD-H and OD-H columns changed their performance, which was subsequently restored by the incorporation of amine.