Determination of proteins using the p-acetylchlorophosphonazo-barium(II) complex as a spectroprobe.

A novel spectrophotometric method has been developed for the determination of proteins using the p-acetychlorophosphonazo (CPA-pA)-barium(II) complex as a spectroprobe. In the pH range of 2.0-2.8, the absorbance of the CPA-pA-barium(II) complex at 649 nm is greatly decreased by protein. The absorbance decrease is in proportion to the concentration of protein in the range of 0-20 mg/L. The apparent molar absorptivities are 1.56 x 10(6), 1.70 x 10(6) and 6.04 x 10(5) L mol(-1) cm(-1) for bovine serum albumin (BSA), human serum albumin (HAS) and ovalbumin (OVA), respectively. The method is reproducible and simple, and has been used to determine total protein in human sera. The results are in agreement with those obtained by the pyrocatechol violet (PV)-Mo(VI) method, with relative standard deviations of 2.5-3.5% (n=6).