Enantioseparation of amino acid amides on an (S)‐N‐(3,5‐dinitrobenzoyl)leucine‐N‐phenyl‐N‐propylamide‐bonded silica in normal phase CEC

Abstract

(S)-N-(3,5-Dinitrobenzoyl)leucine-N-phenyl-N-propylamide-bonded silica was used as a chiral stationary phase for separation of enantiomers of some racemic pi-acidic and pi-basic amino acid amides in normal phase capillary LC (CLC) and CEC. For generation of EOF in CEC, different amounts of water were added to n-hexane-isopropanol (IPA) eluents. Influences of added water and composition of polar modifier on retention, enantioselectivity and resolution were studied. Generally better separation was obtained in the eluents of lower water content. Shorter retention and better enantioselectivities were observed in the eluents of higher IPA content, whereas resolution became lower as IPA content was increased. Enantioselectivities were comparable but resolutions were much better in CEC than CLC.

Synthesis of 5‐(1,2,3‐Triazol‐4‐yl)‐2′‐deoxyuridines by a Click Chemistry Approach: Stacking of Triazoles in the Major Groove Gives Increased Nucleic Acid Duplex Stability

“…These developments include chip‐based enantioselective separations (see an example in Fig. 5) 50–52, the use of new stationary phases and/or background electrolytes for chiral CE and CEC 53–58, new chiral selectors 59–61, multi‐capillary arrays and methods that combine in a single step on‐line stacking and derivatization of enantiomers 64, 65. It is expected that the development of these new approaches and their applications in food analysis will be an important help to overcome some of the mentioned limitations of chiral‐CE.…”

Chiral separation of amides of amino acid on a (S)‐N‐(3,5‐dinitrobenzoyl)leucine‐N‐phenyl‐N‐propylamide‐bonded silica using nonaqueous capillary electrochromatography

“…3, retention is much longer in 40:60 v/v% n-hexane-IPA containing 7% water than in 100% ACN. In NP eluents with the smaller amount of added water retention times were excessively long [28]. As can be seen in Table 1, retention in 100% ACN is much shorter than that in 40:60 v/v% n-hexane-IPA containing 7% water.…”

“…We recently reported the separation of a set of p-acidic and p-basic racemates of a-amino acid amides on CSP 1 by NP-CEC in eluents of n-hexaneisopropanol (IPA) mixtures containing varying amounts of water in order to generate EOF [28]. Despite excellent enantioselectivity and resolution, elution times were excessively long due to the very small EOF generated even with the added water in the mobile phase.…”

Enantioselective capillary electrochromatography: Recent developments and new trends

“…(S)-N-(3,5-dinitrobenzoyl)leucine-N-phenyl-N-propylamide-bonded silica was used in [44] to perform separations of various p-acidic and p-basic amino acid amides in both NPLC and NP-CEC modes. To generate an EOF in CEC mode, the authors describe that the addition of water was necessary, without using any electrolyte.…”