Interaction between chloroauric acid and berberine hydrochloride investigated by resonance Rayleigh scattering spectrum and its analytical applications

In a pH = 2.0 HCl-NaOAc buffer solution, when berberine cation reacted with chloroauric acid anion by electrostatic force and hydrophobic force to form an ion association complex, the Resonance Rayleigh Scattering (RRS) intensity could be enhanced greatly and a new RRS spectrum appeared. The maximum RRS peak was at 370 urn and the other RRS peak was located at 277 nm. There is a linear relationship between the RRS intensity and the berberine concentration in the range of 1.83 X 10(-8) similar to 5.0 X 10(-6) mol/L. The method is very sensitive and the detection limit (3 sigma/K) for berberine hydrochloride is 1.83 X 10(-8) mol/L (7.5 ng/mL). The optimum condition and the effect of coexisting substances have been discussed and the results show that the method also has good selectivity. Based on RRS spectrum of the ion association complex, a highly sensitive, simple and rapid method for the determination of trace amounts of berberine has been developed and applied to the determination of berberine in pharmaceuticals and goldthread extracts with satisfactory results. Furthermore, the reasons for enhancement of RRS were discussed.