Sensitive determination of bromate in ozonated and chlorinated water, and sea water by gas chromatography-mass spectrometry after derivatization

► Bromate reacts with chloride to bromine, which reacts with 2,6-DMP to 4-bromo-2,6-DMP. ► The formed 4-bromo-2,6-DMP was very sensitive and quantitative by GC-MS. ► LOD of bromate is 0.02 μg/L in chlorinated water, ozonated water, and sea water.