Sensitive enantiomeric separation of aliphatic and aromatic amines using aromatic anhydrides as nonchiral derivatizing agents.

New pre-column derivatizing reagents: phthalic anhydride, 3-nitrophthalic anhydride, diphenic anhydride, 1,8-naphthalic anhydride and diphenylmaleic anhydride have been developed for resolving chiral compounds having amine groups. Although all of these agents produce derivatives with high molar absorptivities, the later two also fluoresce. Upon derivatization, aromatic analytes containing free carboxylic groups are produced. Both of these moieties enhance chiral recognition on cyclodextrin-based columns. The derivatization reaction is carried out at room temperature by shaking a buffered aqueous solution of a sample with an acetonitrile solution of the reagent. The reaction is fast and proceeds without any detectable racemization. The labeled compounds have favorable chromatographic properties which are demonstrated by resolution of a number of chiral compounds on cyclodextrin-bonded phases operated with non-aqueous polar organic eluents. The selectivity and good efficiency of this system contributes to its high sensitivity and in its applicability for detecting low levels of enantiomeric impurities. The detection limit is in the picomole range and less than 0.1% enantiomeric impurities can be determined in some cases.