Ultra Pressure Liquid Chromatography-Negative Electrospray Ionization Mass Spectrometry Determination of Twelve Halobenzoquinones at ng/L Levels in Drinking Water

We report here the characterization of twelve halobenzoquinones (HBQs) using electrospray ionization (ESI) high resolution quadrupole time-of-flight mass spectrometry. The high resolution negative ESI spectra of the twelve HBQs formed two parent ions, [M + H+ + 2e(-)], and the radical M-center dot. The intensities of these two parent ions are dependent on their chemical structures and on instrumental parameters such as the source temperature and flow rate. The characteristic ions of the HBQs were used to develop an ultra pressure liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method. At the UPLC flow rate (400 mu L/min) and under the optimized ESI conditions, eleven HBQs showed the stable and abundant transitions [M + H+ + 2e(-)] -> X- (X- representing Cl-, Br-, or I-), while dibromo-dimethyl-benzoquinone (DBDMBQ) showed only the transition of M-center dot -> Br-. The UPLC efficiently separates all HBQs including some HBQisomers, while the MS/MS offers exquisite limits of detection (LODs) at subng/rnL levels for all HBQs except DBDMBQ, Combined with solid phase extraction (SPE), the method LOD is down to ng/L. The results from analysis of authentic samples demonstrated that the SPE-UPLC-MS/MS method is reliable, fast, and sensitive for the identification and quantification of the twelve HBQs in drinking water.