Determination of Bromide and Bromate Ions in the Presence of Standard Ions by Suppressed Ion Chromatography

Highly sensitive, selective and naked-eye detection of bromide and bromate using distance-based paper analytical device

Bromine (Br) can usually be found as a bromide (Br‾) form contained in drinking water. Bromate (BrO₃‾) formation often occurred during the ozonation process in the presence of Br‾. BrO₃‾ is classified as a potential human carcinogen, so both the Br‾ and BrO₃‾ concentrations must be strictly controlled before and after an ozone-based treatment procedure, respectively. This work reports on distance-based paper analytical devices (dPADs) that have been modified with silver hexagonal nanoprisms (AgNPrs) for highly sensitive and selective determination of both Br‾ and BrO₃‾. The measurement of BrO₃‾ is based upon its conversion to bromine vapor (Br₂) when gauged with a paper-based headspace extractor (PAD-HS) that is coupled with dPADs (PAD-HS-dPADs). For Br‾ analysis, O₂ plays an important role in the change from Br‾ to Br₂ within an acid media. Br₂ changes rapidly in water to give us HBrO which is a strong oxidizing agent of AgNPrs. Then, the oxidative reaction of the AgNPrs (pink color) within the presence of Br‾ and BrO₃‾ establishes both silver bromide (AgBr) and the silver nanosphere (AgNPs, yellow color), which can then be easily observed as a change of a pink color band to a yellow color band by the naked eye. Quantification of Br‾ and BrO₃‾ is then achieved by measuring the length of the yellow color band. Under the optimal conditions, the calibration curve will be linear in the range of 25 μg L^-1 to 2 mg L^-1, and from 0.5 to 50 μg L^-1 for Br‾ and BrO₃‾, respectively. The naked-eye detection limits were found to be 10 and 0.5 μg L^-1 for Br‾ and BrO₃‾, respectively. The proposed dPADs for the Br‾ and BrO₃‾ detection exhibited an exceptional sensor performance combined with a low detection limit. They also have the benefits of ease of use, an instrument-free convenience, coupled with portability and a low-cost efficiency. Consequently, our sensing device should be applied to the low-level detection of Br‾ and BrO₃‾ in real samples, including drinking water, rice, and flour.