Investigation On The Galvanic Cell Generated Electrochemiluminescence And Its Analysis Application

In recent years, electrogenerated chemiluminescence (ECL) has become an important and valuable detection method in analytical chemistry. ECL is the luminescence generated by relaxation of exited state molecules that are produced during an electrochemically initiated reaction. Light emitted during electrolysis was first observed by Dufford et al. in 1927 for solutions of Grignard compounds in anhydrous ether, and subsequently by Harvey in 1928 for luminol in alkaline solution. Many of the subsequent publications concentrate on the investigation of the mechanism and nature of ECL, especially of polyaromatic hydrocarbons and metal complexes.It has been proved that ECL is for analytical applications and increasing investigations resulted in highly sensitive and selective detection methods. ECL allows the detection of analytes at low concentrations over a wide linear range. This is partly due to the electrochemical excitation during ECL reactions. In general reactive species formed electrochemically, diffuse from the electrode and react, either with each other or with chemicals in the bulk solution, to produce light from a ECL reaction in the vicinity of the electrode. The absence of an excitation light source produces a low background signal even without additional instrumentation to cut out scattered light from the excitation source. This allows a highly sensitive detection without expensive instrumentation. The electrochemical initiation of the ECL reaction also introduces great temporal control over the reaction. Variations of the potential allow further control over the reaction and can improve selectivity. The generation oflight in the vicinity of the electrode gives improved spatial control for the sensitive detection of analytes. Many analytical methods such as high performance liquid chromatography, liquid chromatography, capillary electrophoresis and flow injection analysis require the addition of reagents in separate streams to produce CL. This often results in expensive instrumentation, sample dilution and peak broadening. Above drawback can be overcome by in situ generation of the reactants. The detection of light also enables multi-parameter detection and various species can be detected simultaneously using lifetime or wavelength discrimination. Some electrochemiluminescent compounds like ruthenium complexes are recycled during the reaction and can emit a number of photons. This not only increases the sensitivity, but it also helps conserve the reagents. Particularly when immobilised, these recyclable compounds can be used for reagentless durable sensors. In comparison to electrochemical detection methods, ECL is not subject to electrical interferences, and to chemiluminescence, ECL reactions introduce a large number of additional advantages over CL, such as great control over the reactions.Despite the large theoretical potential of ECL discussed above, only certain classes of ECL reactions have found widespread applicability in analytical science. The most important reaction is the ECL reaction of ruthenium complexes, particularly tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)32+) and its derivatives. Another important ECL system is the reaction of luminol. Its sensitivity towards hydrogen peroxide allows use in many enzymatic sensors. In most of the cases, the requirement of organic solvents limits the analytical applications of PAHs ECL. ECL generated on cathodic of oxide covered electrodes has been developed recently with the feature of simultaneously detecting a number of different molecules via wavelength and lifetime discrimination. Instrumentation for ECL systems is mainly self-designed and there has been a trend towards miniaturization over the last few years.In this thesis, the research work focused on the development of instrumentation miniaturization for ECL determination. Up to now, all of the reference techniques for ECL generation were carried out by employing an external potential supplier. The size and expense of the potential supplier normally used in research work limited the...