ELECTROSPRAY ION CHROMATOGRAPHY TANDEM MASS-SPECTROMETRY OF OXYHALIDES AT SUB-PPB LEVELS

An electrospray ion chromatography-tandem mass spectrometry (IC-MS/MS) method has been developed for simultaneous analysis of oxyhalide ions (chlorite, chlorate, bromate, iodate) in water, Oxyhalide ions are ex tracted, from pretreated sample, in solid phase extraction (SPE), usin g an ion exchange column, Elution with water/methanol ammonium nitrate eluent is performed on-line with negative ion electrospray mass spect rometry detection, Sample pretreatment is required in order to remove any major ions that displace oxyhalides during SPE, consisting of elim inating SO42-, Cl-, and HCO3- with ion exchange resins. Oxyhalide ion fragmentation yields mass spectra with successive oxygen losses, Isoto pe contribution allows the selection of two precursor ions per analyte (except IO3-), highly enhancing the selectivity of the method, fluent ion choice is discussed, particularly because most of the tested ammo nium salts were shown to be chlorate contaminated, In water samples, t he limits of quantitation are 0.05 (BrO3- and ClO3-), 0.5 (IO3-), and 1.0 mu g/L (ClO2-). In some ammonium salts, the microgram per kilogram level is reached for chlorate impurity quantitation.