Determination of tiopronin based on the enhancement of Ru(bpy)₅²⁺ co-reactant electrochemiluminescence

It was found that tiopronin could strongly enhance the electrochemiluminescence of tris(2,2'-bipyridine) ruthenium(II) (Ru(bpy)3(2+)) in alkaline solution on a bare Pt electrode, based on which a sensitive, simple and rapid method for the determination of tiopronin was established. Under the optimal conditions, the logarithm of ECL enhancement has a linear relationship with the logarithm of tiopronin concentration in the range from 2.0×10(-7) to 2.0×10(-4) mol L(-1) with a detection limit of 1.0×10(-8) mol L(-1) (S/N= 3), and the relative standard deviation of 1.6% (n=7, c=5.0×10(-6) mol L(-1)). The proposed method has been applied to the determination of tiopronin in pharmaceutical preparations and the results were satisfactory with recoveries of 91.7±1.7%, 98.3±1.0% and 100.8±0.5%, respectively, for three different concentration levels (0.61 μmol L(-1), 6.1 μmol L(-1) and 12.2 μmol L(-1)). According to the study of electrochemical behavior, ECL behavior and ECL emission spectrum of Ru(bpy)3(2+)/tiopronin system, a possible ECL mechanism was proposed.