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Peak splitting in the CE separation of enantiomers caused by organic solvents in the sample
Author(s) -
Stapf Fabian I.,
Oehme Michael,
Kiessig Steffen,
Schwarz Maria A.,
Kálmán Franka
Publication year - 2007
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.200700270
Subject(s) - enantiomer , chemistry , analyte , aqueous solution , solvent , electrolyte , impurity , phase (matter) , aqueous two phase system , chromatography , analytical chemistry (journal) , organic chemistry , electrode
Two robust chiral standard separation systems were developed for the analysis of the chiral purity of chemically different model compounds applied in homogeneous asymmetric hydrogenation catalysis. Sulfated CDs were used as chiral selectors as they allow the analysis of neutral, acidic as well as basic compounds in the same electrophoretic system. Poorly water‐soluble amines were dissolved in different organic solvent/buffer mixtures. Reproducibly, depending on the amount of organic solvent in the sample solution, peak splitting occurred and/or more peaks than expected were observed, implying impure model compounds. The dependence of the “chiral purity” on experimental parameters, e.g. , kind and amount of sample solvent, length of injection plug, inner surface modification of the capillary, kind of sulfated CD, hydrophobicity, and basicity of the analytes, etc. was investigated. It is gathered that different equilibrium constants of the strong binding basic analytes and highly sulfated CD complex in the organic phase of the injection plug and the aqueous electrolyte phase are resulting in two different mobility zones for each enantiomer. It follows that each enantiomer is showing two peaks instead of one. Experimental strategies are shown to avoid these peak splitting/artificial impurity effects and obtain the “real” chiral purity picture of the samples.