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IODO-ACID DISINFECTION BY-PRODUCTS IN DRINKING WATER: DOES LC/ESI-MS/MS OFFER AN ADVANTAGE OVER GC/NCI-MS?
Citation:
RICHARDSON, S. D., F. FASANO, J. J. ELLINGTON, F. G. CRUMLEY, K. BUETTNER, J. J. EVANS, B. C. BLOUNT, L. K. SILVA, F. L. CARDINALI, M. J. PLEWA, E. D. WAGNER, G. W. LUTHER III, AND T. J. WAITE. IODO-ACID DISINFECTION BY-PRODUCTS IN DRINKING WATER: DOES LC/ESI-MS/MS OFFER AN ADVANTAGE OVER GC/NCI-MS? Presented at 20th Annual Tandem Mass Spectrometry Workshop, Lake Louise, AB, CANADA, November 28 - December 01, 2007.
Impact/Purpose:
(1) Use a toxicity-based approach to prioritize and identify DBPs that show the greatest toxic response. (2) Comprehensively identify DBPs formed by different disinfectant regimes for the 'Four Lab Study'. (3) Determine the mechanisms of formation for potentially hazardous bromonitromethane DBPs.
Description:
As part of a recent Nationwide Disinfection By-Product (DBP) Occurrence Study, iodo-acids were identified for the first time as DBPs in drinking water disinfected with chloramines. The iodo-acids identified included iodoacetic acid, bromoiodoacetic acid, (E)-3-bromo-3-iodo-propenoic acid, (Z)-3-bromo-3-iodo-propenoic acid, and (E)-2-iodo-3-methylbutenedioic acid. There is concern because toxicity studies have revealed that iodoacetic acid is highly cytotoxic and genotoxic, with a genotoxicity potency 2X higher than bromoacetic acid, the most genotoxic of the regulated haloacetic acids. Also, many drinking water treatment plants in the United States have switched from chlorine to chloramines for treatment. New evidence indicates that the formation of iodinated DBPs will be higher in chloraminated drinking water than in chlorinated drinking water. As a result, we initiated an occurrence study of 23 plants in North America and developed a gas chromatography (GC)/negative chemical ionization (NCI) mass spectrometry (MS) method to measure the iodo-acids in drinking waters across the U.S. GC/NCI-MS was much more sensitive than traditional GC/electron ionization (EI)-MS, and the NCI-MS was ideal for these iodinated compounds, as the iodo-acids were much more sensitive than the corresponding bromo- and chloro-acids. Detection limits of low and sub-ng/L could be obtained using GC/NCI-MS when extracting 1 L of drinking water and derivatizing by methylation. However, recoveries were not in the desired 90-100% range, and it was evident that the derivatization efficiency was the primary reason for less than ideal recoveries. As a result, we investigated the possibility to measure these using liquid chromatography (LC)/electrospray ionization (ESI)-MS/MS so that derivatization would not be necessary, and possibly extraction would not be necessary. A comparison of LC/ESI-MS/MS results to those with GC/NCI-MS will be presented, along with data from the occurrence study and new toxicity results.