Electrochemiluminescence from tris(2,2′-bipyridyl) ruthenium (II) in the presence of aminocarboxylic acid co-reactants

Due to the highly sensitive electrochemiluminescence (ECL), tris(2,2'-bipyridyl) ruthenium(II) (Ru(bpy)(3)(2+)) is often used in the field of bioarrays with the help of co-reactants. However, the generally used co-reactant, tripropylamine (TPA), is toxic, corrosive and volatile. Therefore, the search for safe, sensitive and economical co-reactants is critical. Herein, three aminocarboxylic acids, ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and 2-hydroxyethylethylene diaminetriacetic acid (HEDTA), have been investigated as potential co-reactants for promoting Ru(bpy)(3)(2+) ECL behaviour. A possible ECL mechanism is also presented. The experimental results suggested that the co-reactants have a different ECL behaviour compared to TPA, such as different pH-and surfactant-responses. The detection limits of Ru(bpy)(3)(2+) using NTA, EDTA and HEDTA as co-reactants are 1, 60 and 680 fmol.L-1, respectively. The results indicate that NTA has a much higher efficiency than TPA to excite Ru(bpy)(3)(2+) ECL under their own optimal conditions. NTA could be widely used in many fields because it is less toxic, corrosive and volatile than TPA. Moreover, using Ru(bpy)(3)(2+) ECL, a sensitive method for the detection of aminocarboxylic acids is also developed. An improvement of four orders of magnitude in detection limits is obtained for EDTA compared to the known Ru(bpy)(3)(2+) chemiluminescent methods.