Sensitive screening of bromate in drinking water by an improved ion chromatography ICP-MS method

As a known carcinogen, BrO3− is generated during the sterilization of drinking water by ozone treatment. An improved ion chromatographic technique in tandem with inductively coupled plasma mass spectrometry (IC-ICP-MS) was established for detection of trace-levels of BrO3− in drinking water. Isocratic elution using 40 mM KOH facilitated chromatographic separation of BrO3− and Br− in less than six minutes. The potentially interfering 38Ar40ArH+ and 39K40Ar+ ions at the bromine mass (m/z 79) position were significantly eliminated by oxidization of 79Br+ to 79Br16O+, where the latter ion could be detected at the interference-free mass of m/z 95 by the reaction with reactive N2O gas in a dynamic reaction cell (DRC). Compared to detection of the peak at m/z 79, the signal-to-background ratio of the target ions (at m/z 95) was enhanced by two orders of magnitude. Moreover, the issue of reduced signal intensity of the target ions due to the high-salt mobile phase was alleviated by use of an online argon aerosol dilution (AD) technique. This technique can provide adequate stability and accuracy for bromine speciation in a long-term continuous run (> 27 h). The limit of detection (LOD) was 0.013 μg L− 1 for BrO3−, and the relative standard deviation (RSD) for five injections of 0.5 μg L− 1 BrO3− was in the range of 2.1-4.5%. The analytical results for three water standard reference materials (SRMs) were in agreement with the certified values. The technique was applied to the determination of BrO3− in fifteen bottled water samples and two tap water samples, three of which contained a higher level of BrO3− than the maximum allowable concentration (MAC) of 10 μg L− 1.