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INSTABILITY OF THE WATER DISINFECTION BY-PRODUCT DIBROMOACETONITRILE UNDER PHYSIOLOGICAL CONDITIONS: KINETICS AND PRODUCT CHARACTERIZATION
Citation:
YeowellO'Connell, K., M. Yacopucci, G. Lambert, W. Padgett, AND S Nesnow. INSTABILITY OF THE WATER DISINFECTION BY-PRODUCT DIBROMOACETONITRILE UNDER PHYSIOLOGICAL CONDITIONS: KINETICS AND PRODUCT CHARACTERIZATION. Presented at Society of Toxicology, San Francisco, CA, March 25-29,2001.
Description:
Dibromoacetonitrile (DBAN) is a prevalent haloacetonitrile formed as a byproduct of water chlorination. DBAN is toxic in vivo and genotoxic in vitro and is a mouse skin tumor initiator. However, little is known about its mechanisms of toxicity or genotoxicity or its stability. During our investigation of its reaction products with macromolecules, we observed its elimination and the subsequent formation of two major additional products over time. Concerned that these products may also react with macromolecules, we sought to characterize the kinetics of DBAN degradation and characterize the structures of the observed products. We monitored the elimination of DBAN and formation of products in human blood and physiological buffers using both GC-MS and LC-MS. Although stable under acidic conditions, DBAN readily hydrolyzes at increasing temperature and pH. For example, in phosphate-buffered saline (pH 7.2) DBAN has a half-life of -I year at room temperature, --I month at 37C, and less than I day at 70C. In
human blood at 37C, the half-life was much faster (-2 days) than that observed in buffer. We used mass spectrometry , UV , IR and NMR. spectroscopy to characterize the two major products that resulted from incubation of DBAN (25 mM) in blood, phosphate-buffered saline (pH 7.2 ), or O .2 M sodium acetate (pH 7.2 or 9.5). Under all these conditions, the majority of the DBAN hydrolyzes to form 2,2- dibromoacetamide, while a smaller fraction undergoes a Thorpe condensation, with addition of water and loss of HOBr to form 3-amino-2,4,4-tribromo- but-2-enenitrile. We conclude that DBAN reacts with water non-enzymatically to form additional compounds that may need to be considered when characterizing DBAN's toxicity and mechanisms of action.
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