| Chemiluminescence (CL) is defined as the emission of light from an electronically excited state species which is produced during the course of a chemical reaction, and is observed when the electronically excited product or intermediate formed decays to the ground state with a photon emitted. The CL characteristics often depend on the chemical and spectroscopy characters of the oxidant. However, common oxidants often suffered from different shortcoming. For example, the permanganate systems suffered from an overlap between the CL band and the absorption band of permanganate, which resulted in low CL intensity, while the use of cerium (IV) and NBS was bistable in aqueous solution and hence produce unstable signal. The instability of CL signal can be improved by using instable oxidant synthesized on-line. There are two methods for on-line synthesis of instable oxidant. One is based on on-line electrogenerated oxidant. The electrogenerated oxidant possesses nascent state characteristics, which resulted in high activity. However, this method is only suitable for such inorganic oxidant as Mn (III), Co (III). The other way is based on-line synthesis by mixing of reagent. This method is not only simple, but also retains the reactive activity of instable oxidant. However, few literatures are concerned with on-line synthesis of oxidant in CL analysis. Therefore, it is favorable for us to amplifythe CL research field by using instable oxidant synthesized on line. Compared with CL method, electrochemilummescence (ECL) method not onlyretains the advantages of sensitivity and wide linear dynamic inherent to conventional CL method, but also has some advantages over conventional CL method. First, unstable CL reagent and intermediates can be generated and allows to react in situ as soon as they are formed at the electrode surface. Second, because the reaction can be controlled and manipulated by alteration to the applied potential, it can be used for the selective determination of some substances without separation. Third, electrochemical oxidation ability is continuous and variable under certain chemical condition. Up tonow, however, only few ECL schemes are reported. In addition to the ECL schemes, there are many other ECL schemes. Thus, it is of significant to find and study new ECL scheme and enlarge its application.This thesis contains two parts. Part one is a review of literature, which reports the advance of CL and ECL in analysis during 2000 and 2006.Part two is research report. First, instable agent peroxynitrous acid was synthesized on-line by mixing of nitrite and acid hydrogen peroxide. The peroxynitrous acid exists in three forms: ris-peroxynitrous acid, /ra/w-peroxynitrous acid and excited state peroxynitrous acid. All of them possess high oxidizing and peroxidizing ability, and excited state peroxynitrous acid has high energy. When peroxynitrous acid synthesized on line was mixed with such drug as quinines, quinolones and tryptophan, a stronger CL was observed. The stronger CL was investigated in detail, and the corresponding compounds were determined by flow injection CL method. Second, even though the ECL method was high sensitive, wide linear range and simple equipment required, few ECL reaction schemes were reported. Thus, it was of significance to find new ECL schemes. Two new kinds of ECL scheme, based on successive electro- and chemo- oxidation of oxidable analyte and successive electro-oxidation of oxidable analyte, were proposed and applied to the determination of rifampicin, isoniazid and rutin. Finally, an energy transfer ECL method based on energy transfer from triplet sulfur dioxide that was produced from electrochemical oxidation of sulflte, an energy transfer mediator, to pipemidic acid was proposed. The major contents in this thesis are described as follows:Part I Investigation of peroxynitrous acid weak CL system and its application in CL analysis1. Flow-injection CL determination of chloroquine using peroxynitrous acid as oxidantIn sulfuric acid solution, hydrogen peroxide reacted with nitrite to produce peroxynitrous acid. The formed peroxynitrous acid oxidized chloroquine to give two excited states, excited state 4-quinolinone and excited state 4-hydroxyquinoline. Theexcited state compounds went to their ground states, producing a stronger CL. Based on this phenomenon, a new flow-injection CL method for determination of chloroquine is proposed. The detection limit is 8.6x10"8 mol/L.2. Flow-injection CL determination of fluoroquinolones by enhancement of weak CL from peroxynitrous acidAcidic hydrogen peroxide reacted with nitrite to produce weak CL The weak CL was from excited state peroxynitrous acid. When fluoroquinolones, including ciprofloxacin, norfloxacin and ofloxacin, was present, the weak CL was enhanced. The enhancement was due to energy transfer from excited state peroxynitrous acid to fluoroquinolones. Based on this phenomenon, a flow injection CL method for the determination of ciprofloxacin, norfloxacin and ofloxacin was proposed. The detection limits for ciprofloxacin, norfloxacin and ofloxacin were 4.5x10'8, 5.9x10"8 and 1.1x10'7 mol/L, respectively.3. Flow-injection CL determination of tryptophan through its peroxidation and epoxidation by peroxynitrous acidA flow-injection CL method for the determination of tryptophan was proposed, which was based on an intense CL of tryptophan in hydrogen peroxide-nitrite-sulfuric acid medium. The CL reaction was attributed to peroxidation and epoxidation of tryptophan by peroxynitrous acid, and subsequent decomposition of the formed dioxetane. The limit of detection was 1.8x10'7 mol/L.4. Determination of pipemidic acid based on flow-injection CL due to energy transfer from peroxynitrous acid synthesized on-lineA flow-injection CL method for the determination of pipemidic acid is described. It is based on the enhancement of pipemidic acid on the weak CL from the mixing of acid hydrogen peroxide and nitrite. The detection limit is 6.3x10 mol/L. Part II Investigation of new ECL reaction scheme and its application in ECL analysis 1. A novel ECL based on successive electro- and chemo- oxidationA novel ECL scheme was proposed based on successive electro- and chemo-oxidation of oxidable analyte, which was different from both annihilation andcoreactant ECL schemes in mechanism. Rifampicin was used as model compound. The ECL was attributed to electrochemical oxidation of rifampicin to form semiquinone free radical and then subsequently chemical oxidation of the formed radical by oxidant to form excited state rifampicin quinone. The ECL scheme introduced additional advantages such as high selectivity, simple and convenient operation, and effective avoidance of side reaction that often took place in homogenous CL reaction. In addition, with the ECL in the presence of K2S2O8 as oxidant, a flow-injection ECL method for the determination of rifampicin was proposed. The limit of detection was 3.9X10"8 mol/L.2. ECL determination of isoniazid based on successive electro- and chemo- oxidation In alkaline micellar solution, direct oxidation of isoniazid produced stronger ECL.The ECL was attributed to electrochemical oxidation of isoniazid to form a radical, and sequent chemical oxidation of the formed radical by dissolved oxygen. Based on this, a flow injection ECL method was proposed. The detection limit was 2.9xlO"7 mol/L3. Flow injection ECL determination of rutin based on direct electrochemical oxidationIn alkaline micellar solution, direct oxidation of rutin produced stronger ECL. The ECL was attributed to electrochemical oxidation of rutin to form a semiquinone radical, and sequent electrochemical oxidation of the formed radical to form excited state rutin quinone. Based on this, a flow injection ECL method was proposed. The detection limit was 2.9xlO'7 mol/L.4. ECL determination of pipemidic acid using sulfite as energy transfer mediatorA weak ECL from triplet sulfur dioxide (3SO2*) was observed when sulfite diffused from bulk solution was electrochemically oxidized in sulfuric acid solution on PtC?2 covered Pt electrode. When pipemidic acid was present, the weak ECL was enhanced. The enhanced ECL was attributed to energy transfer from 3SC>2* to pipemidic acid. Based on the enhanced ECL, a flow-injection ECL method for the determination of pipemidic acid was proposed. The detection limit was 3.9X10"8 mol/L.
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