Fluorimetric method for the determination of phenylalanine in serum

Abstract The fluorimetric determination of phenylalanine is based on the enhancement of the fluorescence of a phenylalanine-ninhydrin reaction product by a peptide, leucylalaninc. The method allows phenylalanine to be measured quantitatively in the presence or absence of other amino acids at a final concentration of 10 −7 M. Under the conditions described only 5 μL of normal serum is required for analysis. The method has been applied to the determination of phenylalanine serum levels in adult, pediatric, and phenylketonuric patients. The values found are in good agreement with those reported in the literature using other methods.