Assay of aromatic amino acid enantiomers in rice-brewed suspensions by chiral ligand-exchange CE

Authors

  • Li Qi,

    1. Beijing National Laboratory of Molecular Science, Laboratory of Analytical Chemistry for Life Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, P. R. China
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  • Meirong Liu,

    1. Beijing National Laboratory of Molecular Science, Laboratory of Analytical Chemistry for Life Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, P. R. China
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  • Zhenpeng Guo,

    1. Beijing National Laboratory of Molecular Science, Laboratory of Analytical Chemistry for Life Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, P. R. China
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  • Mingyi Xie,

    1. Beijing National Laboratory of Molecular Science, Laboratory of Analytical Chemistry for Life Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, P. R. China
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  • Changgui Qiu,

    1. Beijing National Laboratory of Molecular Science, Laboratory of Analytical Chemistry for Life Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, P. R. China
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  • Yi Chen Professor

    Corresponding author
    1. Beijing National Laboratory of Molecular Science, Laboratory of Analytical Chemistry for Life Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, P. R. China
    • Institute of Chemistry, Chinese Academy of Sciences, P. O. Box 2709, Beijing 100080, P. R. China Fax: +86-10-62559373
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Abstract

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 DL-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 ZnSO4, 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.

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