Ultrasensitive assay of rhein in medicine based on its enhanced luminol-K3Fe(CN)6 chemiluminescence reaction using the flow injection technique

Determination of the effective components in traditional Chinese medicine is one of the key steps for its identification. In this paper a novel and sensitive chemiluminescence (CL) method for the determination of rhein coupled with flow-injection analysis (FIA) is developed. It is based on the strong sensitizing effect on the weak CL reaction between luminol and ferricyanide in alkaline solution. Under optimal experimental conditions, the relative CL intensity is proportional to the concentration of rhein in the range of 7.0 x 10(-12) - 7.0 x 10(-10) mol L-1 and 1.0 x 10(-9) - 4.0 x 10(-5) mol L-1, the detection limit is 1.478 x 10(-13) mol L-1, and the relative standard deviation (RSD) for 9 parallel measurements of 1.408 x 10(-7) mol L-1 rhein is 3.4%. The method was successfully applied to the determination of rhein in pharmaceutical preparations. The possible mechanism of CL is also briefly discussed.