The Investigation Of The Chemically Modified Electrodes On Electrochemiluminescence Analysis And Its Analyticalapplication

The investigation of the chemically modified electrodes on Electrochemiluminescence analysis and its analyticalapplicationWANG QIIn this thesis, the progress of chemically modified electrode, especially the chemically modified carbon paste electrode, in analytical application, including the fabrication of the based-electrode materials, the new modifying techniques and the modifiers used, are reviewed. In addition, the possible advancement on this aspect is further outlooked in this thesis.Chemically modified electrodes(CME) continue to be a field of exciting research since the middle of the seventies. Many techniques have been developed for preparation of modified surfaces and a variety of modified electrodes have been demonstrated to function as rationally designed. The significant progress has come from covalently linked CME, then the adsorbed CME, recently polymer film electrodes as well as self-assembling membranes(SAMs) being more attractive in their selectivity and stability.While the early monomolecular layers on the electrode surface are often not well coherently organized. The main disadvantages of polymer film electrodes and SAMs are the few modifier to prepare electrode . It needs long time to finish preparation. On the contrary, the concept of just mixing a modifier and other proper additives to make a carbon paste electrode(CPE) is very fast and easy. The electrode surface can be simply polished or cutting to change a new and it is more stable compared with other surface-modified electrodes. Moreover, Chemically modified carbon paste electrode(CMCPE) is advantageous over wide potential window ( -1.4V~ + 1.7V),along with a low residual current and its lower price. Today, It is more popular in analytical application.The key point of CMCPE technique is to develop modifier. A widevariety of different modifier, such as chelating reagent, ion-exchange resin, enzymes, even DNA have been immobilized into the carbon paste electrodes. The modifying techniques are developed from simple mixing to solving modifier into bondant or adsorption. Screen-printing technology can be usefully applied to the mass production of inexpensive, reproducible and sensitive disposable electrode.Not only a great many Metal ions but also organics can be determined using CMCPE.CMCPE can be worked as the detector of FIA and HPLC. There has been demonstrated screen-printing electrode modified with gold is already adapted to microfluidic chip platforms. All these provide new driving force for development of electrochemical analysis.In our research works, we focus our attention on the application of CME in electrogenerated chemiluminescence's analysis. Firstly, based on the bentonite dopped carbon paste electrode , the isoniazid could be sensitively and selectively detected with ECL method. A new concept, to improve the sensitivity of luminol ECL system, based on using chemically modified CPE, was also first developed in this paper. Under the selecting experimental conditions, the relative ECL intensity was linear with isoniazid concentration in the range of 5.0 x 10"9 ~ 8.0 x 10"7mol/L and with a detecting limit of 1.8 * 10~9mol/L. The mechanism of this ECL system is also discussed. Secondly, Hydrocotisone could be determined by screen-printing electrode modified with luminol and CTMAB. The main principle was that this compound could greatly enhance the weak ECL signal arising from the electrochemical oxidation of luminol in weak alkaline medium. Based on these observations and the choices of the experimental conditions, the relative ECL intensity was linear with hydrocotisone concentration in the range of 2.0 * 10"7g/mL - 1.0 * 10"5 g/mL and with a detecting limit of 5.6 * 10"8 g/mL; Finally, the weak ECL signal, generated from elelctrochemical reducing luminol on the surface of the carbon paste electrode, was greatly enhanced by the H2O2, Mo(VI) andV(V). Based on these findings, a new sensitive and selective ECL method for determination of H2O2,Mo(VI) and V( V) was developed, respectively.