Trichloramine (NCl3) is one of the major causes of the chlorine odor in drinking water. In the present study, a method was developed for analysis of NCl3 concentration in water using headspace gas chromatography/mass spectrometry (HS–GC/MS). For quantification of NCl3, m/z of 51 was selected because other major m/z of NCl3 were also observed as fragments of trichloromethane (CHCl3) and the peaks of NCl3 and CHCl3 overlapped on the chromatogram. The limit of quantification for NCl3 was set to 15 μg-Cl2/L. The calibration curve of NCl3 was expressed as a quadratic curve because of the partial NCl3 decomposition. NCl3 concentrations in chlorinated ammonium solution were determined by HS–GC/MS and titration using N,N-diethyl-p-phenylenediamine and ferrous ammonium sulfate (DPD/FAS), and the results using the two methods were similar at pH 6 and 7. However, at pH 8, NCl3 was detected using HS–GC/MS, but not using DPD/FAS titration. NCl3 concentrations in nine tap water samples were determined using HS–GC/MS and ranged from < 15 to 46 μg-Cl2/L. The results of the present study indicated that HS–GC/MS is applicable to determination of NCl3 in drinking water.

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