| Electrochemiluminescence(also called electrogenerated chemiluminescence, ECL) is the process whereby species generated at or near an electrode surface undergo high-energy electron-transfer reactions to form excited states, producing light as excited molecules decay to the ground state. ECL not only retains the high sensitivity inherent to chemiluminescence but also possesses the potential controllability, and has been widely used in areas such as clinical diagnosis, pharmaceutical analysis, food and water testing. The detection cell and chemiluminescent system are two key components of an ECL detection system. The majority of detection cells for ECL detection systems have been developed on the basis of the conventional three-electrode electrochemical cell. ECL cells are generally designed to be sufficiently large to obtain high emission intensities by consuming a mass of samples in static detection mode. The working electrode also needs to be constantly polished to prevent the adsorption of impurities and the formation of an oxide film on its surface. Coupling capillary electrophoresis to ECL can achieve high emission efficiencies with small sample solutions. However, the distance between the working electrode and capillary needs to be proofed under a microscope using a ruler prior to each detection, which will affect the repeatability of the experimental results. In addition, the detection result is also sensitive to high-voltage electric fields. Flow-injection ECL has some advantages, such as rapid analysis, simple operation and being easy to clean. Nevertheless, in the detection cell, only a small portion of these samples close to the working electrode can participate in reactions to form excimers. On the other hand, most of ECL analysis systems are based on Ru(bpy)32+/tripropylamine, the tripropylamine has several disadvantages,such as toxic, volatile, slightly soluble in water and low oxidation rate. To overcome the aforementioned problems, we made a major improvement for MPI-E electrochemiluminescence analyzer to develop a high efficient jet ECL analysis system using Ru(bpy)32+/n-butyldiethanolamine. Subsequently, the propoed ECL analysis system was used for determination of ractopamine in swine urine and alpha fetoprotein in clinical serum. The specific research contents as follows:In the second chapter, we redesigned a novel jet detection cell based on the coupling capillary electrophoresis electrochemiluminescence which capillary is fixed on the front of working electrode. In the cell, samples were jetted on an electrode through a fixed tiny steel neeedle on the front of the working electrode and then overflowed from a thin tube. In addition, we added a syringe pumb to the MPI-E electrochemiluminescence for rapid detecting and washing. Using n-butyldiethanolamine as a coreactant for Ru(bpy)32+can make up the shortage of traditional TPr A. Under the optimal conditions, the logarithm of ECL intensity was observed to be linearly proportional to the concentration of Ru(bpy)32+in the range of 10-10 to 10-5M(r=0.9999), with a detection limit of 5 × 10-11M(S/N=3). The relative standard deviation for 10-8 M Ru(bpy)32+was 1.20%(n=11). Compared to the sensitivity and linear response range obtained using the traditional static detection mode, those obtained using the jet analysis technique were better; in addition, the detection limit of Ru(bpy)32+was reduced by approximately one order of magnitude with the jet analysis technique.In the third chapter, based on the strong inhibitory effects of ractopamine for tris(2,2’-bipyridyl)ruthenium(Ⅱ)/n-butyldiethanolamine system, a rapid and sensitive method for the determination of ractopamine residues was constructed. To go a step further and validate the practicability of the detection system for analysing actual samples, we carried out a interference experiment. Most interferents had no significants effect on the ECL intensities of tris(2,2’-bipyridyl)ruthenium(Ⅱ)/n-butyldiethanolamine system, and the inhibitory effects of urine acid was also less than 5%. The recoveries of ractopamine reference standard were between 93.60 % and 107.40 %, and further validated the practicability of the proposed method. Under a low concentration of n-butyldiethanolamine, quenching effects of ractopamine on the ECL intensity was probably due to the consumption of n-butyldiethanolamine radical by the oxidation products of ractopamine. The limit detection of the proposed method for ractopamine was 5 × 10-10g/m L(S/N=3), and with a wide linear region and excellent reproducibility. The method consumed low sample volumes, tested rapidly and provided accurate results, and has shown promise for the determination of ractopamine residual in livestock and food.In the chapter four, we constructed a sandwich-type ECL immunosensor based on magnetic beads and Ru(bpy)32+-doped silica nanoparticles for further applying to the detection of low concentration biological samples. Using magnetic beads as the solid phase carrier can make the separating and enriching of immune complexes become more convinent, and thus reduce the background noise. Employing Ru(bpy)32+-doped silica nanoparticles to label secondary antibody could futher amplify signals and achieve the detection of low concentration biological samples. In addition, this lable mode not only retained the ECL effeciency of Ru(bpy)32+, but also avoided the loss of the activity of the antibody. The limit detection of the proposed method for determination of alpha-fetoprotein was 2pg/m L. The analysis results were coincident with reference values of Unicel DXI 800, and suggested that the proposed method was a very promising system for ultrasensitive bioanalysis. |
PDF Full Text Request