Color Reaction of Phenylpyruvic Acid with Fe3+ and Its Application

In aqueous dimethyl sulfoxide(DMSO) medium, phenylpyruvic acid reacts with Fe3+ in the presence of acetate acid and forms a stable blue _ green complex with maximum absorbance at wavelength of 640 nm. The effects of medium acidity, amount of color reagent, and certain metallic ions and compounds on the color reaction were studied. Beer'law is obeyed in the range of 0.10～0.50 mg sodium phenylpyruvic per 5 mL color reaction solution, and the apparent molar absorption coefficient is 2.04×103 L·mol-1·cm-1. Applied to the determination of sample solution and the transaminase activity in the process of L _ phenylalanine(L _ Phe) production by transamination, the proposed method proves to be simple, rapid and sensitive, and can be used as an effective means to monitor the process of L _ Phe production.