Simultaneous determination of phenylalanine and tyrosine in peripheral capillary blood by HPLC with ultraviolet detection.

OBJECTIVES: Phenylalanine (Phe) and tyrosine (Tyr) are the most reliable indicators for the diagnosis of phenylketonuria (PKU). The purpose of this study is to establish a simple and rapid method for the determination of Phe and Tyr in peripheral capillary blood from newborns and children by high performance liquid chromatography with ultraviolet detection (HPLC-UV). METHODS: Peripheral blood specimens were taken from newborns or children by heel stick or skin puncture on the fingers. Blood samples were deproteinized by equal volume of 5% perchloric acid. Amino acid separation was carried out on a Hypersil C8 column. The mobile phase containing 5% acetonitrile (v/v) was run at a flow rate of 1.5mL/min. Phe and Tyr were determined in the ultraviolet detector at 210nm. RESULTS: The determination was within 10.0min. The linear range was from 6.0 to 1512.0μmol/L for Phe and 5.5 to 1250.0μmol/L for Tyr. Although Phe and Tyr levels from peripheral blood samples were relatively lower than those from serum or plasma, the data showed a good agreement between them. CONCLUSION: The method we developed is simple, rapid and convenient. It is useful for screening and diagnosis of PKU in newborns and children.