Recent developments in gas chromatography – mass spectrometry (GC-MS) allow using high resolution – accurate mass (HRAM) Orbitrap mass analyzers to discover organic volatile and semi-volatile compounds in a given sample. This type of detectors provides the resolving power, mass accuracy and sensitivity required to carry out this task in complex matrices. This work presents the application of this novel technology to characterize iodine containing disinfection by-products (DBPs) in DBP mixtures of disinfected waters. Iodo-DBPs formed during disinfection of iodide containing waters may pose a health risk for the population exposed to them, as some of them were proven to be more genotoxic and cytotoxic than the corresponding brominated and chlorinated analogues. Many iodo-DBPs still belong to the unknown fraction of the DBP spectrum generated during water chlorination. In this sense, complete characterization of the DBP mixtures is necessary to assess their potential risk for human health. For iodo-DBP characterization, DBP mixtures were generated in controlled lab-scale chlorination and chloramination reactions. Two different water samples with different bromide and iodide content were used. Disinfected waters were extracted using XAD resins and final extracts were analysed under electron ionization with the Q-Exactive GC mass spectrometer using 60,000 full wide at half maximum resolution (measured at m/z 200). Iodo-DBP characterization was based on HRAM data and fragment rationalization. Automatic peak detection, spectral deconvolution and compound identification using spectral library matching was performed with the TraceFinder software. However, due to the large number of compounds detected following this approach, a mass filter at m/z 126.90392 (iodine mass) was employed to limit the chemicals of interest only to those containing iodine. This workflow allowed the identification with different confident levels of up to 11 different iodo-DBPs (one new iodo-DBP among them) in the DBP mixtures generated. Analysis of these extracts using softer ionization techniques may contribute to further characterize iodo-DBPs in these mixtures. Formation of iodo-DBPs in terms of abundance and diversity of compounds was enhanced during water chloramination, and was observed to be different in the waters tested due to their different characteristics in terms of iodine and bromine content and aromacity content.

Use of gas chromatography orbitrap mass spectrometry for small molecule discovery: Iodinated disinfection byproducts as case study

253rd National Meeting (2017)

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