Determination Of Melamine And Malachite Green Based On ECL Of Ru(bpy)₃²⁺

Electrochemiluminescence (also called electrogenerated chemiluminescence and abbreviated ECL) is the process whereby species generated at electrodes undergo high-energy electron-transfer reactions to form excited states that emit light. Electrochemiluminescence (ECL) of tris(2,2'-bipyridine)Ruthenium(Ⅱ) [Ru(bpy)32+] has been attracting much attention in biochemical analysis, clinical diagnosis and scientific research because of its high sensitivity, wide dynamic range, stability and simplicity etc.Firstly, ECL of Ru(bpy)32+ at bare and single-wall carbon nanotube (SWNT) modified glassy carbon (GC) electrode has been employed for determination of melamine at first time. the dynamic range is 1.0x10-10-1.0x10-5M at bare GC electrode in pH 10 phosphate buffer, and the melamine detection limit is 1.0x10-10M (S/N≥3). The detection limit can be reduced further to 1.0x10-13M at SWNT modified GC electrode. ECL of Ru-PTZ linked with electron donor group phenothiazine and bimetallic ruthenium complex Ru-8C-Ru are applied to the determination of melamine, and the tests demonstrate that broader dynamic range and lower detection limit can be observed. The proposed ECL method was applied to the determination of melamine added into a commercial milk sample; the recovery is quite satisfied with good reproducibility and stability. All these provide a possibility to develop a novel ECL melamine detection method in the food.Secondly, ECL of the parent Ru(bpy)32+ and bimetallic ruthenium tris-bipyridyl complex at gold (Au) electrode has been employed for determination of malachite green (MG) and leucomalachite green (LMG) at first time. For Ru(bpy)32+, it gave a linear response (R2=0.9992) for malachite green concentration from 1.0x10-8-1.0x10-5M with a remarkable detection limit of 1.0×10-8M at Au electrode in pH 10 borate buffer. The detection limit can be reduced further to 1.0x10-12 M for the bimetallic ruthenium complex Ru-8C-Ru and Ru-10C-Ru. It is much lower compared to the other detection methods. The proposed method was applied to the determination of malachite green added into a pond water sample with good reproducibility and stability. All these provide a possibility to develop a novel ECL detection method on MG and LMG in the water samples and aquatic products.Thirdly, ECL of a series of bimetallic ruthenium complexes Ru-8c-Ru, Ru-10c-Ru, Ru-12c-Ru and Ru-14c-Ru with different length carbon chain as bridge group, have been studied. Tripropylamine (TPrA) and 2-(dibutylamino) ethanol (DBAE) as the coreactant, the results demonstrate that the largest ECL enhancement was achieved by using of the ten carbon chain linked Ru-10c-Ru, which exhibits more than 12 times stronger than that of the reference compound Ru(bpy)32+(measured at Au working electrode)...