Resonance Rayleigh Scattering Spectra of Thorium (Ⅳ)-bisazo Dye of Chromotropic Acid-protein Systems and Their Analytical Applications

摘要

In acidic medium, thorium (Ⅳ) can react with a bisazo dye of chromotropic acids such as arsenazo Ⅲ (AA Ⅲ), arsenazo M (AA M), chlorophosphonazo Ⅲ (CPA Ⅲ) and chlorosulphonphenol S (CSP S) to form an anionic chelate which further interacts with some proteins to produce a complex. This results in a significant enhancement of intensity of the resonance Rayleigh scattering (RRS) and the appearance of a new RRS spectrum. There are a few obvious RRS peaks in the range of 400-470 nm and the most intensive peak of them is located at 470 nm. The Intensity of RRS is directly proportional to the concentration of protein in the range of 0―1.6 μg·mL~(-1) for Th(Ⅳ)-CPA Ⅲ system, 0―2.8 μg·mL~(-1) for Th(Ⅳ)-AA M system, 0―2.0 μg·mL~(-1) for Th(Ⅳ)-AA III system and 0―0.28 μg·mL~(-1) for Th(Ⅳ)-CSP S system, respectively. The detection limits for BSA (3σ) are 10.7 ng·mL~(-1) for Th (Ⅳ)-CPA III, 6.3 ng·mL~(-1) for Th(Ⅳ)-CSP S, 13.6 ng·mL~(-1) for Th(Ⅳ)-AA III and 22.1 ng·mL~(-1) for Th(Ⅳ)-AA M, respectively. This new RRS method has high sensitivity and fairly good selectivity and can be applied to the direct determination of proteins in human serum with satisfactory results..