A sensitive method for the determination of ultra trace levels of reactive bromine species in water using LC-MS/MS

The purpose of this study was to develop and validate a sensitive method for the determination of ultra trace levels of reactive bromine species (RBS) in water. To derivatized RBS, water samples were transferred into vials pre-fortified with an appropriate dose of derivative reagent 3,5-dimethyl-1H-pyrazole (DMPZ). RBS in water samples could be rapidly and stoichiometrically (1:1) derivatized to 4-bromo-3,5-dimethyl-1H-pyrazole, which was directly analyzed on an ultra performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry. Parameters influencing the derivatization efficiency including reaction time, temperature, DMPZ dose, and pH were optimized to be: a molar concentration ratio of DMPZ to RBS a 100:1, pH 5-10, and reaction for 10 min at room temperature. In addition, near 100% of RBS was recovered when using water with salinity of 0-55 as the spiking matrices, suggesting that salinity had negligible effect on the derivatization efficiency. Under the optimized conditions, interday and intraday analyses showed that the recoveries of RBS ranged from 88.0% to 109.8% for samples spiked with 18.0-540 pmol L-1 of RBS, with relative standard deviations less than 3.7%. The method limit of detection and limit of quantification for RBS were 5.8 pmol L-1 and 18.0 pmol L-1, respectively. Compared with currently available methods, our method greatly improved the analytical sensitivity by lowering the limit of detection for more than 100 times. The developed method displayed high reliability and reproducibility in the analysis of ultra trace levels of RBS in seawater and other real fresh water samples.