Detection of chlorinated and brominated byproducts of drinking water disinfection using electrospray ionization-high-field asymmetric waveform ion mobility spectrometry-mass spectrometry

The lower limit-of detection for low molecular weight polar and ionic analy tes using electrospray ionization-mass spectrometry (ESI-MS) is often sever ely compromised by an intense background that obscures ions of trace compon ents in solution. Recently, a new technique, referred to as high-field asym metric waveform ion mobility spectrometry (FAIMS), has been shown to separa te gas-phase ions at atmospheric pressure and room temperature. A FAIMS ins trument is an ion tilter that may be tuned, by control of, electrical volta ges, to continuously transmit selected ions from a complex mixture. This ca pability offers significant advantages when FAIMS is coupled with ESI, a so urce that generates a wide variety of ions, including solvent clusters and salt adducts, In this report, the tandem arrangement of ESI-FAIMS-MS is use d for the analysis of haloacetic acids, a class of disinfection byproducts regulated by the US EPA. FAIMS is shown to effectively discriminate against background ions resulting from the electrospray of tap water solutions con taining the haloacetic acids. Consequently, mass spectra are simplified, th e selectivity of the method is improved, and the limits of-detection are lo wered compared with conventional ESI-MS. The detection limits of ESI-FAIMS- MS for six haloacetic acids ranged between 0.5 and 4 ng/mL in 9:1 methanol/ tap water (5 and 40 ng/mL in the original tap water samples) with no precon centration, derivatization, or:chromatographic separation prior to analysis .