Sensitive and simple determination of protein by resonance Rayleigh scattering with 4-azochromotropic acid phenylfluorone

At pH 0.5-1.8 the resonance Rayleigh scattering (RRS) spectrum of 4-azochromotropic acid phenylfluorone has a peak at 337 nm, and the RRS intensity is enhanced by small amounts of protein due to the binding interaction of protein and the dye. On the basis of this, a highly sensitive assay for protein is established. There are linear relationships between the enhancement of RRS intensity and the concentrations of bovine and human serum albumins over the range 0.2-4.0 mg l(-1). The detection limits (3 sigma) for bovine and human serum albumins are 68 and 75 ng ml(-1), respectively. The method is characterized by high sensitivity, short reaction period, simplicity and good stability of the chemical system. The results for diluted human serum and urine obtained by this method with a relative standard deviations; of 1.7-2.8% (n = 6), are consistent with those obtained by the Coomassie brilliant blue G-250 assay. (C) 2000 Elsevier Science B.V. All rights reserved.