Mechanistic investigations of cinchona alkaloid-based zwitterionic chiral stationary phases.
Novel zwitterionic cinchona alkaloid-based chiral selectors (SOs) were synthesized and immobilized on silica gel. The corresponding brush-type chiral stationary phases (CSPs) were characterized as zwitterionic ion-exchange-type materials and exhibited remarkable enantioselectivity for their zwitterionic target analytes, viz. underivatized amino acids and aminosulfonic acids. We rationally designed structural modifications on the strong cation exchange (SCX) subunit of the zwitterionic SO and investigated the influence on chiral recognition power for amphoteric solutes. SOs with chiral isopropyl- or cyclohexyl-moieties in vicinity to the SCX site showed broadest application range by baseline resolving 39 out of 53 test compounds, including α-, β-, and γ-amino acids with different substitution patterns. Furthermore, we introduced two pseudoenantiomeric zwitterionic CSPs which combined the unique features of providing comparable enantioselectivities but reversed enantiomer elution orders. By application of slightly acidic polar organic mobile phases as preferred elution mode, we found that certain amounts of aprotic acetonitrile in protic methanol substantially increased enantioselectivity and resolution of amino acids in a structure-dependent manner.
Department of Analytical Chemistry, University of Vienna, Währinger Strasse 38, 1090 Vienna, Austria.
Reinhard
R
Pell
Siniša
S
Sić
Wolfgang
W
Lindner
D002411:Cation Exchange Resins; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods*; D002852:Chromatography, Ion Exchange / Q000295:instrumentation / Q000379:methods*; D002930:Cinchona Alkaloids / Q000737:chemistry*; D007477:Ions; D013237:Stereoisomerism
D002411:Cation Exchange Resins; D002930:Cinchona Alkaloids; D007477:Ions