Enantioseparation and chiral recognition of α-amino acids and their derivatives on (-)-18-crown-6-tetracarboxylic acid bonded silica by capillary electrochromatography.
Capillary electrochromatography was employed for enantioseparation of α-amino acids and their derivatives. (-)-18-Crown-6-2,3,11,12-tetracarboxylic acid bonded on the silica was used as the chiral stationary phase and methanol/Tris-citric acid (20 mM, pH 3.0-4.5) (20:80, v/v) was used as mobile phase. The enantioseparation performance was discussed and structure-chiral separation relationship were tried to be explained. The enantiomeric resolution was increased when the pH of the mobile phase decreased or hydrogen of amino acid was substituted with halogen. The resolution of 4-bromophenylalanine was 2.37 at pH 4.5, however, this value was increased to 3.35 at pH 3.0. Bromo- or chloro-substituted phenylalanine tended to show higher resolution than fluoro-substituted one. For fluoro-substituted phenylalanine the resolution was increased in order of 4-, 3- and 2-substituted one. α-Methyltryptamine did not show reasonable separation. As the thermodynamic study is a useful tool to understand the chiral recognition, the temperature effect on the enantioseparation was studied and the thermodynamic parameters were calculated. The most important mechanism of chiral recognition for the analytes tested could be barrier effects based on the thermodynamic calculations. The coefficient of determination between hydrophobicity and separation factor was found to be 0.87, indicating favorable separation with higher hydrophobicity of amino acids.
School of Lifescience, Inner Mongolia University for the Nationalities, Tongliao, China.
Enqi
E
Wu
Kyung Tae
KT
Kim
Sreenivas Kalyan
SK
Adidi
Young Keun
YK
Lee
Jong Woon
JW
Cho
Wonjae
W
Lee
Jong Seong
JS
Kang
D000596:Amino Acids / Q000737:chemistry* / Q000302:isolation & purification*; D053801:Capillary Electrochromatography / Q000379:methods*; D043844:Crown Ethers / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D012822:Silicon Dioxide / Q000737:chemistry*; D013237:Stereoisomerism
D000596:Amino Acids; D043844:Crown Ethers; C090732:18-crown-6 2,3,11,12-tetracarboxylic acid; D012822:Silicon Dioxide