Halogenation of Dissolved Organic Matter: A New Methodology To Quantify and Characterize Bromine and Iodine Incorporation

During the chlorination process, a major pathway of byproduct formation is the incorporation of halogen into organic matter. We developed a methodology based on the coupling of a size exclusion chromatography (LC-SEC) coupled to an elemental detector inductively coupled plasma mass spectrometry (ICP-MS) allowing the quantification of organic iodine and bromine bound to organic matter large molecules (humic substances and building blocks or higher) down to 0.6 and 7.5 μg L–1 for iodine and bromine, respectively, by direct injection of water sample without pretreatment. The application of this methodology showed that the incorporation of halogens to organic matter large molecules reaches a maximum, while the total organic halogenation still increases. The concentration of halogenation sites is estimated to be 1.4 μmol per mg of carbon for the Suwannee River Natural Organic Matter corresponding to the possibility to incorporate into the complex structure either 50 or 110 of bromine and iodine, respectively, per mg of C. The organic bounded halogens have been found to not be stable to reducing agents; ascorbic acid and sulfite lead to a decrease of up to 20% of the organic bromine or iodine concentrations. Similarly, basic conditions degrade the structure.