Characterization and Determination of Chloro- and Bromo-Benzoquinones as New Chlorination Disinfection Byproducts in Drinking Water

摘要

We report the characterization and determination of 2,6-ndichloro-1,4-benzoquinone and three new disinfectionnbyproducts (DBPs): 2,6-dichloro-3-methyl-1,4-benzo-nquinone, 2,3,6-trichloro-1,4-benzoquinone, and 2,6-di-nbromo-1,4-benzoquinone. These haloquinones are sus-npected bladder carcinogens and are likely producednduring drinking water disinfection treatment. However,ndetection of these haloquinones is challenging, and con-nsequently, they have not been characterized as DBPs untilnrecently. We have developed an electrospray ionizationntandem mass spectrometry technique based on ournobservation of unique ionization processes. These chloro-nand bromo-quinones were ionized through a reductionnstep to form [M H] under negative electrospraynionization. Tandem mass spectra and accurate massnmeasurements of these compounds showed majornproduct ions, [M H HX] ,[M H HX CO] ,n[M H CO] , and/or X (where X represents Cl ornBr). The addition of 0.25% formic acid to waternsamples was found to effectively stabilize the halo-nquinones in water and to improve the ionization fornanalysis. These improvements were rationalized fromnthe estimates of pKa values (5.8 6.3) of these halo-nquinones. The method of tandem mass spectrometryndetection, combined with sample preservation, solidnphase extraction, and liquid chromatography separa-ntion, enabled the detection of haloquinones in chlori-nnated water samples collected from a drinking waterntreatment plant. The four haloquinones were detectednonly in drinking water after chlorination treatment, withnconcentrations ranging from 0.5 to 165 ng/L, but werennot detectable in the untreated water. This method willnbe useful for future studies of occurrence, formationnpathways, toxicity, and control of these new haloge-nnated DBPs.