Assay of aromatic amino acid enantiomers in rice-brewed suspensions by chiral ligand-exchange CE.
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 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 microg/mL for Typ, 1.00-120 microg/mL for Phe, and 2.50-200 microg/mL for Tyr, with linear regression coefficient all over 0.999. The LOD (S/N=3) was 0.15 microg/mL for Typ, 0.50 microg/mL for Phe, and 1.25 microg/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.
Qi
Li
L
Beijing National Laboratory of Molecular Science, Laboratory of Analytical Chemistry for Life Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing, PR China.
Liu
Meirong
M
Guo
Zhenpeng
Z
Xie
Mingyi
M
Qiu
Changgui
C
Chen
Yi
Y
D024322:Amino Acids, Aromatic / Q000032:analysis*; D024361:Amino Acids, Basic; D019075:Electrophoresis, Capillary / Q000379:methods* / Q000592:standards; D007202:Indicators and Reagents; D008024:Ligands; D012275:Oryza / Q000737:chemistry*; D013237:Stereoisomerism
D024322:Amino Acids, Aromatic; D024361:Amino Acids, Basic; D007202:Indicators and Reagents; D008024:Ligands