Spectrophotometric Determination of Phosphate Ion with Ferric Salt of Tetraphenylporphine-trisulfonic Acid

Abstract

A new indirect spectrophotometric method for the determination of phosphate ion by the use of solid ferric salt of tetraphenylporphine-trisulfonic acid (TPPSFe) was developed. The method is based on the measurement of the absorbance of TPPS liberated from TPPSFe at its Q band (procedure A) or its Soret band (procedure B). Phosphate ion ranging from 10 to 50μg and from 4 to 20μg could be determined based on the absorption coefficients of 8.2×10³ at 512nm (procedure A) and 2.2×10⁵ at 434nm (procedure B). The advantages of this method are its simple procedure and mild conditions. Procedure A was successfully applied to the determination of phosphate ion liberated from glucose-1-phosphate by acid phosphatase.