Quantitative determination of proteins by the Rayleigh light-scattering technique after optimization of the derivation reaction with Arsenazo-DBS Original Research Article

This paper researched the determination of proteins with 2-(2-arsonophehenylazo)-7-[(2,6-dibromo-4-sulfophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid (Arsenazo-DBS) by Rayleigh light-scattering (RLS). The reaction parameters, such as acidity, volume of buffer solution and concentration of Arsenazo-DBS, were examined by orthogonal array design (OAD). Under optimal conditions, the weak RLS of Arsenazo-DBS and BSA can be enhanced greatly and two enhanced RLS signals were produced at 340–350 and 400–420 nm. Based on this reaction, a new quantitative determination method for proteins has been developed. This method is proved to be very sensitive (the determination limits are 0.077 μg ml−1 for bovine serum albumen (BSA) and 0.074 μg ml−1 for human serum albumen (HSA)), rapid (<2 min), simple (one step) and tolerance of most interfering substances. The effects of different surfactants were also examined. The amount of proteins in human serum samples was determined and the maximum relative error was no more than 2% and the recovery was between 95 and 105%.