Separation and Retention Behavior of Aromatic Carboxylic Acid Isomers by High‐Performance‐Liquid‐Chromatography Using β‐Cyclodextrin Bonded Phase with Diamine‐s‐Triazine Moiety

A β‐cyclodextrin (β‐CD) bonded phase with diamine‐s‐triazine moiety was prepared. The separation and retention behavior of the isomers of five aromatic carboxylic acids, including toluic acid, aminobenzoic acid, nitrobenzoic acid, hydroxybenzoic acid, and naphthoic acid were investigated by a high‐performance liquid chromatography (HPLC) using the β‐CD bonded phase prepared. The influence of mobile phase pH in the range of 2.7‐3.6 on the retention of these analytes was examined. The isomers of the aromatic carboxylic acids, with the exception of nitrobenzoic acid, were optimally and effectively separated at pH 2.7, while the three isomers of nitrobenzoic acid could be well separated at pH 3.3. Compared with the chromatographic results obtained previously on the amine‐s‐triazine‐β‐CD bonded phase, the retention factors of the isomers of aromatic carboxylic acid on the diamine‐s‐triazine‐β‐CD bonded phase increase to a relatively much greater extent. Thus, the functionality of the spacer arm of the bonded phase playing an important role in the retention of aromatic carboxylic acid isomers is demonstrated. The results also imply that the hydrogen‐bonding interaction and the mechanism of anion exchange sorption as well may contribute significantly to the retention mechanisms.