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Enantiomeric separation of chiral dipeptides by CE‐ESI‐MS employing a partial filling technique with chiral crown ether
Author(s) -
Xia Shifei,
Zhang Lan,
Lu Minghua,
Qiu Bin,
Chi Yuwu,
Chen Guonan
Publication year - 2009
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.200800799
Subject(s) - acetic acid , enantiomer , chemistry , chromatography , crown ether , methanol , electrolyte , ether , amino acid , nuclear chemistry , ion , analytical chemistry (journal) , stereochemistry , organic chemistry , electrode , biochemistry
Enantiomer of chiral dipeptides were separated by CE‐ESI‐MS in a bare fused‐silica capillary using (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid (18C 6 H 4 ) as the chiral selector. As 18C 6 H 4 is a kind of nonvolatile chiral selector, in order to prevent from 18C 6 H 4 into the ion‐source of CE‐ESI‐MS, a partial filling technique was employed in this study. Some dipeptides with one chiral center or two chiral centers, such as DL ‐Leu‐ DL ‐Leu, D ‐Ala‐ D ‐Ala and L ‐Ala‐ L ‐Ala, Gly‐ D ‐Phe and Gly‐ L ‐Phe were used to evaluate this CE‐ESI‐MS system. Optimized conditions were achivevd with 2.0 mol/L acetic acid (pH 2.15) as the running electrolyte, 5 mM 18C 6 H 4 in 3.0 mol/L acetic acid (pH 2.00) was injected hydrodynamically (50 mbar for 960 s) before sample injection. In total 7.5 mM acetic acid in 80% v/v methanol–water was used as the sheath liquid, and 20 kV applied voltage was used. Under the optimum conditions, these dipeptides were separated and detected. LODs (defined as S / N =3) of this method were 0.20, 0.10, 0.05 and 0.10 μmol/L for D ‐Ala‐ D ‐Ala, L ‐Ala‐ L ‐Ala, DL ‐Leu‐ DL ‐Leu, Gly‐ L ‐Phe and Gly‐ D ‐Phe, respectively. The RSDs ( n =7) of the method were 0.68–2.08% for migration times and 2.32–5.24% for peak areas. The proposed method was also successfully applied to the enantioselective analysis of these dipeptides in the spiked serum samples with satisfactory results.