Study On Antioxidant Capacity In Fruit Samples By Sequential Injection Coupled With Chemiluminescence For The Determination Of Free Radical

In the past years, the importance of antioxidants in the protection of organisms or tissues, or of nonliving systems against oxidative stress has become evident. Detection of scavenging free radical capacity is a kind of good method, which evaluates the antioxidant ability in fruit samples. Free radical oxidation and the resulting intermediate product seriously injury biofilm, vitamins, protein and function of living cells, many of them have been recognized carcinogens, and now many diseases are related to free radicals. Therefore, the establishment of a simple, rapid, sensitive and reliable method with high selectivity has important practical significance, which assesses the ability of antioxidant in samples.Chemiluminescence (CL) method is an attractive and powerful detection technique owing to its analytical advantages such as low detection limit, very high sensitivity, wide linear dynamic range, fast response and simple equipment. Chemiluminescence analysis is the use of a chemiluminescent substance oxidant oxidized to form an intermediate excited state, when the excited state intermediate back to the stable ground state, emit photons. The luminol is a luminescent substrate in chemiluminescence. It is light with a lot of oxides such as oxygen, hypochlorous acid, sulfur, peroxide reaction. it has become one of the hottest research fields in the analysis of trace and ultra trace amount of inorganic, biological and organic materials. At the same time, sequential injection analysis (SIA) was developed as a branch of sampling means of FIA or second generation FIA with the advantages of high degree of automation, low consumption and good reproducibility. When chemiluminescence detection was coupled with SIA analysis, its features were reserved, and the shortcomings, such as inconvenience of reaction process control and poor repeatability caused by fast reaction, were overcome. Combination CL with SIA remarkably improved the repeatability, accuracy and analytical frequency of the determination results. In this dissertation, the sequential injection coupled with chemiluminescence detection technique was proposed and applied to the determination of the ability to clear the superoxide anion radical and hydroxyl radical in samples. And it has achieved satisfactory results.The first chapter introduces the nature of superoxide anion radical, hydroxyl radical, generation method. analytical methods for detection of free radicals such as fluorescence spectrometry, chemiluminescence spectrophotometry, electrochemical methods, high performance liquid chromatography, and electron spin trapping have a more detailed description. It also describes the nature of the characteristics of sequential injection analysis technology, and the rapid screening of antioxidant capacity flow injection analysis method described in detail, including clear ABTS·+, DPPH·, and electrochemical methods.The second chapter of the dissertation described a sequential injection coupled with chemiluminescence for the determination of suppression capacity of three fruit samples to superoxide anion radical. The principle is the pyrogallol auto-oxidation under alkaline conditions, to generate superoxide anion radicals, which react with luminol to produce chemiluminescence Under the optimum condition, the linear response range between the concentration of ascorbic acid and its suppression ratio to superoxide anion radical is 5.0×10-5-6.0×10-4 mol/L with a correlation coefficient of 0.9935. The detection limit (3?) is 3.03×10-5 mol/L. The relative standard deviation (RSD) is 0.95% at 5.0×10-4 mol/L levels(n=11). The sampling frequency is 200 samples per hour. The method was applied to the determination of antioxidant activities for three fruit samples.The third chapter of the dissertation described a sequential injection coupled with chemiluminescence in determination of hydroxyl radical in fruit samples. Under the optimum condition, the linear response range is 2.0×10-4-3.0×10-3 mol/L with a correlation coefficient of 0.9993. The detection limit (3?) is 9.7×10-5mol/L. The relative standard deviation (RSD) is 0.66% at 5.0×10-4 mol/L levels.The method was applied to the determination of antioxidant capacity in Fruit SamplesIn the last chapter, a summary for the characteristic of sequential injection coupled with chemiluminescence detection technique was described.