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Effect of the Tethering Groups of Chiral Stationary Phases Based on (+)‐(18‐Crown‐6)‐ 2,3,11,12‐Tetracarboxylic Acid on the Liquid Chromatographic Resolution of β‐Amino Acids

Abstract Effect of the tethering groups of chiral stationary phases (CSPs) based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid on the liquid chromatographic resolution of β‐amino acids was investigated by resolving various β‐amino acids on two CSPs having different tethering groups. In the resolution of β‐amino acids with the mobile phase of 50% methanol in water, containing 10 mM acetic acid or 10 mM sulfuric acid, it was found that acetic acid is more effective as an acidic modifier than sulfuric acid on the CSP, which has an N‒H amide tethering group, while sulfuric acid is more effective than acetic acid on the CSP which has an N‒CH3 amide tethering group. In addition, the elution orders for the resolution of 3‐amino‐3‐phenylpropionic acid on the two CSPs were opposite to each other. From these chromatographic resolution results, it was concluded that the tethering groups of the CSPs based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid play some important role in the chiral recognition of β‐amino acids, even though the exact role of the tethering groups is not clear at the present time. However, the chromatographic trends for the resolution of selected β‐amino acids with the variation of the content of organic and acidic modifiers in aqueous mobile phase and the column temperature were generally consistent on the two CSPs.