Direct determination of phenylalanine in serum extracts of phenylketonuria patients by reversed-phase high-performance liquid chromatography.

A method for direct determination of phenylalanine (Phe) in serum extract by reversed-phase high-performance liquid chromatography with an octadecylsilane column has been devised. Phe is monitored at 220 nm with a UV detector. The mobile phase is a mixture of methanol and water (10:90) with added phosphoric acid and potassium dihydrogen phosphate and has a pH value of 4.3. The minimum detectable amount is 6 ng. The average contents of Phe found for healthy adults and children are 12 and 15 micrograms/ml respectively. Phe contents of sera of three phenylketonuria children are about 10 to 15 times higher than these values.