Spacer length effect of a chiral stationary phase based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid.
A new chiral stationary phase (CSP) containing 11 methylene-unit spacer was prepared by bonding (+)-(18-crown-6)-2,3,11,12-carboxylic acid to aminoundecylsilica gel. The new CSP was superior to the one containing three methylene-unit spacer in the resolution of alpha-amino acids, beta-amino acids, amines, and amino alcohols in terms of both the separation (alpha) and the resolution factors (R(S)). In the resolution of alpha-amino acids on the new CSP containing a long spacer, the retention factors (k(1)) were quite small compared to those on the CSP containing a short spacer. However, in the resolution of relatively more lipophilic beta-amino acids, amines, and amino alcohols, the retention factors (k(1)) were generally greater on the CSP containing a long spacer than on the CSP containing a short spacer. All of these resolution behaviors have been rationalized by the effective competition of the ammonium ions (R-NH(3)(+)) generated by the residual undecylamino groups of the new CSP under acidic condition with the ammonium ions (R-NH(3)(+)) of analytes for the complexation inside the cavity of the crown ether ring of the CSP and the effective lipophilic interaction between the CSP and the relatively more lipophilic analytes.
Hyun
Myung Ho
MH
Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Pusan, Republic of Korea. mhhyun@pusan.ac.kr
Hun Kim
Do
D
D000438:Alcohols / Q000737:chemistry; D000596:Amino Acids / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D043844:Crown Ethers / Q000737:chemistry*; D006838:Hydrocarbons; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008956:Models, Chemical; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013997:Time Factors
D000438:Alcohols; D000596:Amino Acids; D043844:Crown Ethers; D006838:Hydrocarbons; D000644:Quaternary Ammonium Compounds; C090732:18-crown-6 2,3,11,12-tetracarboxylic acid; C030011:carbene; D008697:Methane