A selective and sensitive assay of berberine using total internal reflected resonance light scattering technique with fluorescein at the water/1,2-dichloroethane interface.

An assay of berberine (BE) was developed with good selectivity and sensitivity based on the total internal reflected resonance light scattering (TIR-RLS) signals from water/1,2-dichloroethane (H(2)O/DCE) interface. Under optimal conditions, amphiphilic complex formed by BE and fluorescein (Flu) was adsorbed to H(2)O/DCE interface, resulting in good separation of BE from the coexisting foreign substances in aqueous phase and significant enrichment of BE at the interface. This enriched species at the interface was found corresponding to enhanced TIR-RLS signals located at 370.0 nm. Proportional relationships were established between the enhanced TIR-RLS intensity and the BE in the range of 3.2 x 10(-9) to 3.2 x 10(-6) mol l(-1) with the limit of detections (3sigma) being 1.3 ng ml(-1). Favorable sensitivity of TIR-RLS technique was demonstrated superior to that of high-performance liquid-chromatography (HPLC) method. The feasibility of the proposed technique was validated by the satisfactory performance of intra-assay and inter-assay BE in tablets.