Method development for quantification of bromochloramine using membrane introduction mass spectrometry

Abstract

During chloramination of bromide-containing water, the main brominated-amine formed is bromochloramine (NHBrCl). To date, there is no analytical method, free of interference, allowing its accurate quantification. The major reason is that it is not possible to produce a pure NHBrCl solution. In this study, we report a method allowing the accurate quantification of NHBrCl with membrane introduction mass spectrometry (MIMS). Firstly, the molar absorption coefficient for NHBrCl was determined by quantifying NHBrCl as 2,4,6-tribromophenol by HPLC-UV and comparing the results with the direct UV response at 320 nm. A molar absorption coefficient of 304 M-1cm-1 was obtained. The results obtained by direct UV measurements were compared to the MIMS signal recorded at m/z 131 corresponding to the mass of the molecular ion, and used to establish a calibration curve. A limit of detection of 2.9 µM was determined. MIMS is the only method enabling the unambiguous quantification of NHBrCl, as it is based on m/z 131, while with other analytical techniques, other halamines can interfere, i.e. overlapping peaks with direct UV measurements, reaction of several halamines with colorimetric reagents or phenols. This analytical method will benefit to the scientific community by allowing for example, further mechanistic study on the contribution of NHBrCl to the formation of toxic disinfection by products.