Resonance Rayleigh method for the determination of proteins with Orange G

In pH 0.6 - 2.0 HCl-sodium acetate buffer solution, proteins react with an acidic monoazo dye such as Orange G, Methyl Orange, Methyl Red and Orange IV to form a combination product. This results in a significant enhancement of resonance Rayleigh scattering (RRS) and a new RRS spectrum appears. Owing to the fact that Orange G-protein system is the most sensitive, it was taken as an example to study. The RRS spectral characteristics of its combination product and the optimum condition for the reaction were investigated. The intensity of RRS is directly proportional to the concentration of protein in the range of 0 - 5.0 microg/mL. The method has high sensitivity; its detection limits are 2.6 ng/mL for BSA, 3.4 ng/mL for HAS and 7.1 ng/mL for alpha-chymotrypsin, respectively. A new method for the determination of trace amounts of proteins on the basis of RRS spectra has been developed.