title: Simultaneous measurement of phenylalanine and tyrosine by high performance liquid chromatography (HPLC) with fluorescence detection.
abstract: OBJECTIVE
  An HPLC method was developed to quantify serum concentrations of phenylalanine and tyrosine simultaneously using fluorescence detection without derivatization.
  
  
  METHODS
  Serum protein is precipitated with trichloroacetic acid, 0.015mM dihydrogen-phosphate solution is used for separation on reversed-phase C18 material, and acetonitrile is avoided. Both amino acids are monitored utilizing their natural fluorescence at 210nm excitation and 302nm emission wavelengths.
  
  
  RESULTS
  One analytical run is completed within 7min. Lower detection limit for Phe and Tyr is 0.3μM. Comparison of the new method with a classical HPLC method for total amino acids and using UV-absorption detection reveals a highly significant relationship for Phe and Tyr.
  
  
  CONCLUSIONS
  The new HPLC method allows rapid and very sensitive measurement of phenylalanine and tyrosine concentrations.
authors.affiliation: Division of Biological Chemistry, Biocenter, Medical University, Innsbruck, Austria.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Neurauter
authors.forename: Sabine
authors.initials: S
authors.lastname: Scholl-Bürgi
authors.forename: Astrid
authors.initials: A
authors.lastname: Haara
authors.forename: Simon
authors.initials: S
authors.lastname: Geisler
authors.forename: Peter
authors.initials: P
authors.lastname: Mayersbach
authors.forename: Harald
authors.initials: H
authors.lastname: Schennach
authors.forename: Dietmar
authors.initials: D
authors.lastname: Fuchs
mesh_terms: D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005453:Fluorescence; D006801:Humans; D057230:Limit of Detection; D010649:Phenylalanine / Q000097:blood*; D014443:Tyrosine / Q000097:blood*
chemical_list: D014443:Tyrosine; D010649:Phenylalanine
keywords: Fluorescence monitoring; HPLC; Phe/Tyr; Phenylalanine; Tyrosine