Electrochemiluminescent behavior of melatonin and its important derivatives in the presence of Ru(bpy)(3)(2+)

Melatonin and some of its important derivatives were found to be able to enhance the ECL of Ru(bpy)₃²⁺ in an alkaline Britton–Robinson buffer solution. The optimum conditions for the enhanced ECL, such as the selection of applied potential mode, type of buffer solution, pH effect and effect of Ru(bpy)₃²⁺ concentration have been investigated in detail in this paper. Under the optimum conditions, the enhanced ECL is linear with the concentration of melatonin and its derivatives over the wide range, and the detection limit for these compounds was found to be in the range of 5.0 × 10^?8 to 1.0 × 10^?10 mol L^?1. The proposed procedure was applied for the determination of drug in tablets with recoveries of 85–93%. A possible mechanism for the enhanced ECL of Ru(bpy)₃²⁺ by melatonin and its derivatives was proposed, and the relationship between molecular structure of melatonin and its derivatives and the enhanced ECL behavior was also discussed.