Resonance Rayleigh-scattering method for the determination of proteins with some monoazo dyes of chromotropic acid

In a weak acid medium, protein reacts with a monoazo dye of chromotropic ac id, such as Chromazol KS (CALKS), Acid Chrome Dark Blue (ACDB), Chrome Blue SE (CBSE), Acid Chrome Blue K (ACBK), Chlorophosphonazo I (CPAI), Arsennaz o I (AAI) and Chromotrope 2R (CT2R), to form a combination product. This re sults in a significant enhancement of the resonance Rayleigh-scattering (RR S) intensity, and the corresponding RRS spectrum appears. The characteristi cs of the RRS spectra of the combination products and the optimum condition s for the reactions were investigated. The intensity of RRS is directly pro portional to the concentration of protein in a certain range. The RRS metho ds have high sensitivity for the determination of protein, the detection li mits for bovine serum albumin (BSA) are 10.0 - 30.2 ng/ml, and the sensitiv ity order is CALKS > AAI approximate to CPAI > ACBK approximate to CT2R > A CDB > CBSE. The selectivity for CALKS has been examined, and the method was applied to the determination of a mug amount of protein in a synthetic sam ple with satisfactory results.