New energy resources that can replace petroleum diesel are needed and biodiesel may be an excellent substitute. During storage and use, biodiesel can oxidize and form peroxides, leading to degradation of the fuel. It is therefore important to determine the peroxide content of the fuel. In this thesis the triphenylphosphine method, which involves GC-MS analysis has been compared to the standard iodometric method which involves titration with sodium thiosulfate. Working standards were made to see how well the iodometric method worked and also in order to make a calibration curve in GC-MS. Aged samples were then analyzed. The results showed that both methods gave good linearity and repeatability with limits of detection (LOD) and quantification (LOQ) of 0,06 mM and 0 17-0,65 mM respectively. However, the iodometric method seemed more circumstantial since it needed a lot of solvents and different reagents. The triphenylphosphine method was on contrary very simple to use and did not require too much preparation work. The latter also showed better reproducibility. In conclusions, both methods can be used in evaluating the peroxide content of biodiesel, but the triphenylphosphine method has the advantages of higher simplicity and better reproducibility.

No description available.

No description available.

Infection of fully expanded leaves of tobacco with INF1 causes the appearance of HR lesions within 12 h and progressive to all infection sites after 48 h treatment. Among the POD isozymes, the increase of cationic PODs and anionic PODs is correlated with the rise of lignin contents in INF1-treated leaves, especially cationic PODs (pI 9.5, pI 8.7, pI 8.3, pI 7.8, pI 7.4). It was suggested that the induction of POD activity resulted in part of H2O2 reduction. The increase of cationic (pI 9.5) and anionic (pI 4.4) POD transcripts was correlated with the increased cationic and anionic PODs activity in INF1-treated leaves. Therefore, the increased POD activity is due to the de novo synthesis of the cationic (pI 9.5) and anionic (pI 4.4) PODs in INF1-treated leaves. The increase in cationic pI 9.6 laccase transcript was also correlated with the increased cationic laccase activity in INF1-treated leaves. Our results suggest that laccase might play a major role on lignin biosynthesis at the early stage (6 h), and as the inoculation time was prolonged, peroxidases (especially cationic POD) and laccases will work together on lignin biosynthesis.

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The significant root inhibition of growth in Cd-treated soybean (Glycine max) seedling correlated with the increase of H2O2 levels, PODs and laccases activity. The increase of the activities of PODs (pI 8.8, pI 7.7, pI 5.2, pI 4.5, pI 4.4 and pI 3.7) and laccases (pI 9.2, pI 8.9 and pI 8.3, pI 5.4, pI 4.2 and pI 3.7) are accompanied by a rise of lignin contents in Cd-treated tissues. Our results suggested that laccases work during the early stage of Cd treatment. Laccases and peroxidases work cooperatively in lignin synthesis when the time of Cd treatment was prolonged.

In our study, the decrease of H2O2 levels in wounding-treated tissues of soybean ( Glycine Max ) hypocotyls is accompanied by the enhancement of the POD activity. The POD activity was significantly enhanced 0.5 d after wounding treatment. The laccase activity was significantly enhanced 1-2 d after wounding treatment. The enhancement of POD by mechanical wounding occurred a day earlier than laccase. The increase in activities of POD and laccase is correlated with a rise in lignin contents in wounding-treated tissues. We suggest that in control tissues, laccase might play major role on the lignin biosynthesis, hence, POD by utilizing H2O2 play the major role on the lignin biosynthesis during the wounding process.

Abstract The effect of tannic acid (TA), gallic acid (GA), propyl gallate (PA) and ellagic acid (EA) on DNA damage in human lymphocytes induced by food mutagens, 3-amino-1-methyl-5 H-pyrido (4,3-b)indole (Trp-P-2) and 2-amino-1-methyl-6-phenylimadazo (4,5-b)pyridine (PhIP), and/or H2O2 was evaluated using single-cell electrophoresis (comet assay). The toxicity of these tested compounds on lymphocytes was not found. These compounds did not cause DNA damage at lower concentration of 0.1-10 µg/ml. At a concentration of 100 µg/ml, TA and GA exhibited slight DNA damage, whereas PA and EA showed no DNA damage. TA and its related compounds decreased the DNA damage induced by Trp-P-2 or PhIP at a concentration of 0.1-10 µg/ml. Moreover, the inhibition of H2O2-induced DNA damage increased with increasing concentrations up to 10 µg/ml. DNA repair enzymes, endonuclease III (Endo III) and formamidopyrimidine-DNA glycoslase (FPG) were used to examine the levels of oxidised pyrimidines and purines in DNA damage induced by H2O2, respectively. All the compounds at 10 µg/ml can reduce the level of FPG sensitive sites. However, only EA inhibited the formation of EndoIII sensitive sites. The results indicate that these compounds can enhance lymphocyte resistance towards DNA damage induced by food mutagens or H2O2. Keywords: Tannic acid; Human lymphocyte; Comet assay; Hydrogen peroxide

Factors that affect liquid chemical intervention methods of controlling pathogens on fresh-cut produce were investigated. The relationship between produce tissue structure (intercellular space, cell size, and cell distribution) and the sanitizing effectiveness of liquid chemical treatment was studied. Experiments determined if sanitizer contact with bacteria could be improved through the use of surfactants and different application methods (drop application method, negative pressure differential, and sonication). To test these factors, a model sanitizer, H2O2, and a model microorganism: Salmonella Typhimurium, along with various fresh-cut produce (apple, pear, carrot, and potato) were tested. Microscopic analysis revealed a very complicated pore structure consisting of irregular capillaries. S. Typhimurium was found to survive in all produce tested, and washing did not significantly reduced inoculated bacteria regardless of the bacterial incubation time or produce type. The results showed that a 3% H2O2 solution reduced S. Typhimurium in produce and the solution’s efficiency varied in the following descending order: potato>apple>carrot>pear. In seven min treatments, bacteria were reduced by 2.5 CFU/ml in potato, 2.3 CFU/ml in apple, 1.5 CFU/ml in carrot, and 0.7 CFU/ml in pear. There was no direct evidence on how intercellular space, its percentage or cellular distribution and shape affected efficiency, but some possibilites were discussed. The rate and extent of liquid penetration, and how varying pore diameter in each cell or air space prevent complete chemical treatment penetration were also analyzed. It was determined that bacterial density has a slight effect in bacterial reduction but this depends on type of produce inoculated. The use of surfactants did not improve bacterial reduction in either washing or chemical treatments, and neither did the use of drop application method or temperature differential. On the other hand, applying the chemical treatment with a surfactant while using a sonicator did improve the treatment’s efficiency. This thesis provides a number of factors to be considered when designing a chemical treatment and a guideline for further research in areas such as rate and extent of liquid chemical treatment penetration into fresh-cut produce.

Thesis (Ph. D.)--School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 2004. Directed by L. Gregory Huey. / Includes bibliographical references (leaves 74-89).