The enhanced electrochemiluminescence of lucigenin by some hydroxyanthraquinones

Several hydroxyanthraquinones (emodin, rhein and physcion) were found to strongly enhance the cathodic electrochemiluminescence (ECL) of the lucigenin by scanning under the mode of differential pulse voltammetry. The enhanced intensity was linear with the concentrations of rhein, emodin and physcion. The linear calibration ranges of 8.0 × 10−8 to 2.0 × 10−6, 3.0 × 10−7 to 8.0 × 10−6 and 1.0 × 10−7 to 1.0 × 10−6 mol/L, the detection limits of 2.1 × 10−8, 1.6 × 10−7 and 5.2 × 10−8 mol/L were obtained for rhein, emodin and physcion, respectively. Potential-resolved ECL was used to study the possible mechanism of the enhancement effect. An electron transfer pathway was found to be involved in the ECL process. It has been confirmed that the reduced hydroxyanthraquinones reacted with dioxygen to give superoxide radical anion which increased the ECL of the lucigenin. Furthermore, these three hydroxyanthraquinones revealed the different enhanced ECL efficiency in the following order: rhein > physcion > emodin.