title: Chromatographic method for determination of the free amino acid content of chamomile flowers.
abstract: OBJECTIVE
  To determine the free amino acid contents of chamomile flowers using reverse-phase high-performance column chromatography preceded by pre-column derivatization with 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC), and to determine the reliability of this method.
  
  
  METHODS
  Derivatization with reconstituted AQC was used to prepare the samples and standards for injection into the chromatography column. The peaks were analyzed by fluorescence detection (λ excitation, 250 nm; λ emission, 395 nm.
  
  
  RESULTS
  Alanine, proline, and leucine were the most abundant amino acids, whereas tyrosine and methionine were the least abundant. The linearity of the method was found to be good with amino acid concentrations of 0.012-0.36 μM. The precision was 0.05-1.36%; average recovery, 91.12-129.41%; and limit of detection, 0.006-0.058 μM.
  
  
  CONCLUSIONS
  The method is reliable for determining the free amino acid content of different types of chamomile flowers.
authors.affiliation: Analytical and Testing Center, School of Pharmacy, Xinjiang Medical University, Urumqi, Xiangjiang, China.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Ma
authors.affiliation: Analytical and Testing Center, School of Pharmacy, Xinjiang Medical University, Urumqi, Xiangjiang, China.
authors.forename: Dongsheng
authors.initials: D
authors.lastname: Zhao
authors.affiliation: Analytical and Testing Center, School of Pharmacy, Xinjiang Medical University, Urumqi, Xiangjiang, China.
authors.forename: Xinxia
authors.initials: X
authors.lastname: Li
authors.affiliation: Analytical and Testing Center, School of Pharmacy, Xinjiang Medical University, Urumqi, Xiangjiang, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Meng
keywords: 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate; Amino acids; Matricaria chamomilla; Matricaria recutita; reversed-phase high performance liquid chromatography