Oxidation, 2,3,7,8-TCDD

Oxidation, Hydrolysis and Reduction. 2,3,7,8-TCDD is not susceptible to hydrolysis at environmental temperatures ( ) and is highly stable to chemical oxidation. TCDD exhibits thermal stability at environmental temperatures. Indeed, the thermal stability of TCDD is such that temperatures of 1400 F to 2400 F are used for efficient (>99.9999%) degradation of 2,3,7,8-TCDD from contaminated soils (30). Reaction rates with hydroxyl radicals have not been measured, although Podoll and co-workers (3 ) esgimaJed the vapor phase rate constant to be on the order of 3 x M s. Using average OH... 

TCDD was catabolized to arene oxides-TCDD intermediates by Pi-450 (P-488) enzyme system. The intermediates bind covalently to nucleophilic macromolecules at such a high rate that further metabolism is... 

Effects of TCDD on macrophages have also been examined. When assessed ex vivo, macrophage functions such as tumor cell lysis, phagocytosis and oxidative burst were not suppressed by exposure to TCDD.9396 101 In other experimental systems, exposure to TCDD increases IL-1 and TNF production by macrophages.99 102 103 However, the ability of TCDD to alter IL-1 and TNF production is likely organ- or stimulus-specific, because in the context of respiratory viral infection, exposure to TCDD had no effect on IL-1 or TNF-a levels.80... 

Abbreviations PAH = polyaromatic hydrocarbon, TCDD = Tetrachlorodibenzo-p-dioxin, PCB = polychlorinated biphenyl, PBB = polybrominated biphenyl, TBTO = tributyltin oxide, DBTO = dibutyltin oxide, TPT = triphenyltin. 

Parathion, Phorate Sulfur oxides, see Malathion Tartaric acid monoamide p-TCCH, see Lindane y-TCCH, see Lindane TCDD, see 2,4,5-Trichlorophenol Terbufos sulfone, see Terbufos Terbufos sulfoxide, see Terbufos Terephthalic acid, see p-Xylene o-Terphenyl, see Phthalic anhydride 2,2, 4,4 -Tetraamino-6,6 -azotoluene, see 2,4,6-Trinitrotoluene... 

TCDD GC NaOH, H2SO4, silica gel, aluminum oxide SP-2330 capillary 200-250 MS... 

Environmental applications of SFE appear to be the most widespread in the literature. A typical example is the comparison of extraction efficiency for 2,3,7,8 -tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) from sediment samples using supercritical fluid extraction and five individual mobile phases with Soxhlet extraction was made (101). The mobile phases, carbon dioxide, nitrous oxide, pure and modified with 2% methanol as well as sulfur hexafluoride were examined. Pure nitrous oxide, modified carbon dioxide and modified nitrous oxide systems gave the recoveries in the acceptable range of 80 to 100%. Carbon dioxide and sulfur hexafluoride showed recoveries of less than 50% under identical conditions. Classical Soxhlet recoveries by comparison illustrated the poorest precision with average extraction efficiencies of less than 65%. Mobile phase choice, still as yet a major question in the science of supercritical fluid extraction, seems to be dependent upon several factors polarity of the solute of interest, stearic interactions, as well as those between the matrix and the mobile phase. Physical parameters of the solute of interest, as suggested by King, must also be considered. Presently, the science behind the extraction of analytes of interest from complex matrices is not completely understood. 

Chen ZH, Hurh YJ, Na HK, Kim JH, Chun YJ, Kim DH, Kang KS, Cho MH, Surh Y-J. 2004. Resveratrol inhibits TCDD-induced expression of CYP1A1 and CYP1B1 and catechol estrogen-mediated oxidative DNA damage in cultured human mammary epithelial cells. Carcinogenesis 25 2005-2013. 

NZ Alsharif Creighton University, Omaha, NE Data from this study will provide a clear indication of the role of oxidative stress in the chronic toxicity of TCDD including its most sensitive target, the immune system NIEHS... 

In addition to drugs, other chemicals, such as polycyclic aromatic hydrocarbons (e.g.. benzolnrlpyrenc.. T-mcthylchol-anthrenc) and environmental pollutants (e.g.. pesticides, polychlorinated biphenyls. TCDD). may induce certain oxidative pathways and, thereby, alter drug re.sponse. -... 

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