Odorous Products of the Chlorination of Phenylalanine in Water:  Formation, Evolution, and Quantification

Abstract

To explain some of the possible origins of an odor episode which took place in a drinking water supply in the region of Paris (France), the chlorination reaction in water of phenylalanine was studied. This amino acid was chosen for first experiments because of its physical and chemical particular properties. Changes in the different byproducts formed were followed by high-performance liquid chromatography (HPLC) over a period of time. N-chlorophenylalanine (mono-N-chlorinated amino acid) and then phenylacetaldehyde were the major products formed for the lower chlorine to nitrogen molar ratios. For Cl/N molar ratios of 1 and beyond, phenylacetonitrile and N-chlorophenylacetaldimine appeared and increased with the chlorination level. N-chlorophenylacetaldimine was quantified by using its difference of stability in various organic solvents. Our attention was first directed to the monochlorinated derivative but further examination indicated that it could not be responsible for odor troubles: it dissociated before reaching the consumer's tap and it was produced at consistently low yields under conditions relevant to drinking water treatment. On the contrary, chloroaldimine appeared 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 microg x L(-1) and it can persist for more than one week at 18 degrees C. It is now suspected of being a source of off-flavor concerns among consumers.

Identification and characterization of phenylacetonitrile as a nitrogenous disinfection byproduct derived from chlorination of phenylalanine in drinking water

“…3 . The chlorophenylacetaldimine was expected to be the precursor of phenylacetonitrile, contrary to the hypotheses proposed by Freuze et al (2004), Scully (1993), McCormick et al (1993), and Nweke and Scully (1989) who all suggested that chloraldimines and nitriles were produced from N,N-dichloroamino acids by competitive pathways for the phenylalanine, valine, and leucine chlorination. Lahaniatts et al (1994) performed reactions at pH 6 and a phenylalanine/chlorine mass ratio of 10:100, followed by GC-MS analysis of an n-hexane extraction of the reaction solution.…”

“…Chlorophenylacetaldimine and phenylacetonitrile were expected to be the main products when the Cl/N molar ratio is greater than 1 according to previous studies Freuze et al, 2004Freuze et al, , 2005. There was a very small peak in the HPLC-MS chromatogram at RT ¼ 15.72 min that appeared in a scan of m/z ¼ 153 and m/z ¼ 155, which is possibly indicative of chlorophenylacetaldimine (MW ¼ 153 and 155 amu represent 35 Cl and 37 Cl, respectively).…”

“…Hrudey et al (1989) identified that aldehydes are associated with a swampy, swimming pool type of odor. Freuze et al (2004) and Conyers and Scully (1993) reported that synthesized chloroaldimine, a nitrogenous chlorination byproduct originating from phenylalanine, possessed a strong swimming pool odor with a floral background. The olfaction properties for synthesized chloroaldimine were determined to have odor threshold concentrations in the low mg/L range by a panel composed of 4 men and 3 women who smelled chlorinated amino acid solutions (Cl/N ratio 2.4).…”

“…The olfaction properties for synthesized chloroaldimine were determined to have odor threshold concentrations in the low mg/L range by a panel composed of 4 men and 3 women who smelled chlorinated amino acid solutions (Cl/N ratio 2.4). When consumers complained of strong chlorinous odors in their tap water, a connection to chloroaldimine DPBs was suspected but the chloroaldimines were not detected in the tap water samples (Freuze et al, 2004(Freuze et al, , 2005.…”

Simultaneous determination of eight common odors in natural water body using automatic purge and trap coupled to gas chromatography with mass spectrometry

“…Taste and odor (T&O) compounds are troublesome in natural waters because they have a terrible malodor influence on the quality of drinking water and aquatic products, causing great economic losses [1][2][3][4]. Recently, it is frequent that consumers strongly complain about the malodor of recreational waters, tap water and aquatic products, especially during the outbreak period of algae blooms [5,6].…”