Determination of proteins at nanogram levels by a resonance light-scattering technique with tetra-substituted sulphonated aluminum phthalocyanine

This is the first report on the determination of proteins with tetra-substituted sulphonated aluminum phthalocyanine (A1S₄Pc) by resonance light-scattering (RLS). At pH 3.0, the weak RLS of A1S₄Pc can be enhanced by the addition of proteins. Based on this, a novel quantitative method has been developed for the determination of proteins in aqueous solutions. Under optimal conditions, the linear ranges of the calibration curves were 0.050-2.0 μg ml^-1 for both human serum albumin (HSA) and human r-IgG. The detection limits were 12.7 ng ml^-1 for HSA and 16.1 ng ml^-1 for human r-IgG. The method has been applied to the analysis of total protein in human serum samples collected from the hospital and the results were in good agreement with those reported by the hospital, which indicates that the method presented here is not only sensitive, simple, but also reliable and suitable for practical applications.