• Journal of Korean Society of Environmental Engineers
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• v.28 no.4
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• pp.402-406
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• 2006

N-Nitrosodimethylamine(NDMA) formation was studied as a function of chloramine concentration at a fixed dimethylamine (DMA) concentration of 0.05 mM at pH 7 and 8. Regression equations were developed by molar ratio of chloramine to DMA. The NDMA formation was dependent on molar ratio(chloramine/DMA) and was different when the ratio is less or greater than 1. The formation of NDMA increased with increasing chloramine concentration and a linear correlation was examined between NDMA concentration and the ratio on a log scale. The developed regression was applied to previously reported data and relative errors ranged from -79 to 163%. Regression equations could provide a potential tool to predict NDMA formation for a simple and quick estimation in water supply systems.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.4
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• pp.390-393
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• 2005

N-nitrosodimethylamine (NDMA), a potent carcinogenic, has recently been observed at drinking water supply systems in USA and Canada. The NDMA formation was studied as a function of chloramine concentration (0.001-0.1 mM) at a fixed dimethylamine (DMA) concentration of 0.05 mM at different initial pH (6, 7, 8). It was found that the NDMA formation rate varied with pH values. The formation of NDMA increased with increasing chloramine concentration and showed maximum yields of 2.4% and 1.6% at pH 7 and 8, respectively. A good correlation ($r^2>0.99$) was observed between the molar ratio (chloramine/DMA) and NDMA formation at pH 7 and 8. Linearity of the NDMA formation appeared to be related to chloramine concentrations.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.2
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• pp.192-196
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• 2007

In this study, a formation of N-nitrosodimethylamine(NDMA), a disinfection by-product, was investigated as a result of monochloramine addition in water. The NDMA formation was studied in terms of pH, dimethylamine(DMA), monochloramine concentration, and nitrogen composition in monochloramine. At a fixed DMA concentration of 0.01 mM or 0.05 mM, the NDMA formed concentration was quite different when the monochloramine to DMA ratio is less or greater than 1. The NDMA formation increased with increasing pH and a ratio of nitrogen composition in monochloramine to total nitrogen composition. At pH 7 and 8, more than five times higher NDMA formation was produced as a result of five times increase in DMA concentration. It was likely that monochloramine could be related to stimulate NDMA formation, if monochloramine may be produced with chlorine disinfection, in water treatment systems.

• Journal of the Korean Chemical Society
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• v.41 no.5
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• pp.234-238
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• 1997

The photochemical reaction of ammonia in deoxygenated aqueous methanol has been investigated at 25$^{\circ}C$ using 184.9 nm UV light. Amination was carried out by irradiating the solution of reaction mixture, and the formation of methoxyamine, hexamine, 1,1-dimethylhydrazine, dimethylamine, formamide, and a small amount of ethylenediamine was observed. In addition to these, carbonyl compounds such as formaldehyde, ethyleneglycol, glyoxal, and hydrazine were also produced. The initial quantum yields of the products were determined and probable mechanisms for the photochemical reaction were presented on the basis of product analysis.

• Korean Journal of Food Science and Technology
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• v.22 no.7
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• pp.748-752
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• 1990

This paper was investigated to elucidate the nitrite-scavenging ability of roasted-barley extracts. Roasted-barley extracts exhibited nitrite-scavenging ability. The nitrite-scavenging ability of roasted-barley extracts showed pH-dependent, and did the highest at pH 1.2 and the lowest at pH 6.0. The roasting temperature and time of barley examined influenced the nitrite-scavenging ability of roasted-barley extracts. The water soluble fraction obtained from barley roasted at $230^{\circ}C$ for 90 min showed higher the nitrite-scavenging effect than the others. Ethanol soluble fraction which is further fractionated from water soluble fraction was most effective in nitrite-scavenging.