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Assay of aromatic amino acid enantiomers in rice‐brewed suspensions by chiral ligand‐exchange CE
Author(s) -
Qi Li,
Liu Meirong,
Guo Zhenpeng,
Xie Mingyi,
Qiu Changgui,
Chen Yi
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.200700281
Subject(s) - enantiomer , chemistry , ligand (biochemistry) , chromatography , food science , stereochemistry , biochemistry , receptor
The aim of this work was to assay seasoning D ‐ or L ‐aromatic amino acids (AAs) in rice‐brewed suspensions, Laozao in Chinese, by chiral ligand‐exchange CE with UV detection and Zn(II) complex as a chiral selecting system. Resolution and peak retention were found to be parallel to the basicity of the AA chiral ligands, and basic L ‐Arg was known to work the best at pH 8.20 compared with L ‐Lys and other AA ligands. Baseline separation of D L ‐aromatic AAs and partially separation of some FMOC‐labeled nonaromatic AAs have been achieved using a running buffer of 5 mM ammonium acetate, 100 mM boric acid, 3 mM ZnSO 4 , and 6 mM L ‐Arg at pH 8.20. The aromatic amino acids in four brands of Laozao were measured in a range of 0.25–20 μg/mL for Typ, 1.00–120 μg/mL for Phe, and 2.50–200 μg/mL for Tyr, with linear regression coefficient all over 0.999. The LOD (S/N = 3) was 0.15 μg/mL for Typ, 0.50 μg/mL for Phe, and 1.25 μg/mL for Tyr. The recovery of the method determined by spiking with the supernates of Laozao as background was 94.0–112.9%. The RSDs of migration time and peak area measured from six injections of tyrosine were 0.2 and 2.7%, respectively, for run‐to‐run, and 1.6 and 3.2%, respectively for day‐to‐day. Interestingly, there were only L ‐Trp, D ‐Tyr, and L ‐Tyr found in the assayed four brands of Laozao. They may serve as an index to recognize the brand of Laozao.