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| - Odorous Products of theChlorination of Phenylalanine inWater: Formation, Evolution, andQuantification
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| - To explain some of the possible origins of an odorepisode which took place in a drinking water supply inthe region of Paris (France), the chlorination reaction inwater of phenylalanine was studied. This amino acid waschosen for first experiments because of its physical andchemical particular properties. Changes in the differentbyproducts formed were followed by high-performance liquidchromatography (HPLC) over a period of time. N-chlorophenylalanine (mono-N-chlorinated amino acid) and thenphenylacetaldehyde were the major products formed forthe lower chlorine to nitrogen molar ratios. For Cl/N molarratios of 1 and beyond, phenylacetonitrile and N-chlorophenylacetaldimine appeared and increased with thechlorination level. N-chlorophenylacetaldimine was quantifiedby using its difference of stability in various organicsolvents. Our attention was first directed to the monochlorinated derivative but further examination indicated thatit could not be responsible for odor troubles: it dissociatedbefore reaching the consumer's tap and it was producedat consistently low yields under conditions relevant todrinking water treatment. On the contrary, chloroaldimineappeared to be a very odorous and water-stable product: it strongly smells of swimming pool with a floral background.The odor detection threshold is about 3 μg·L-1 and itcan persist for more than one week at 18 °C. It is nowsuspected of being a source of off-flavor concerns amongconsumers.
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