Studies on the Photometric Determination of Phenylpyruvic Acid in Urine

Abstract

Abstract 1. At low temperatures and in the absence of light, ferrous ammonium sulfate exerts a stabilizing effect on the reaction between ferric chloride and phenylpyruvic acid. This reaction is not affected by uranyl nitrate, which has been found by us to be an effective precipitant for phosphate when specimens of pathologic urine are being studied. 2. A method for the analysis of phenylpyruvate has been presented and applied to 8 specimens of urine from cases of phenylpyruvic oligophrenia. The method has been shown to possess good reproducibility, stability, and sensitivity. 3. A mechanism has been postulated for the stabilizing effect of ferrous ions involving an equilibrium relationship between the (Fe- PPA) complex, ferrous, and ferric ions. This concept seems to be strengthened by the fact that ferrous ions are continuously produced during the period of growth and decay of the (Fe-PPA) complex.