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Formation and Occurrence of Iodinated Tyrosyl Dipeptides in Disinfected Drinking Water
journal contribution
posted on 2018-02-28, 00:00 authored by Guang Huang, Ping Jiang, Lindsay K. Jmaiff Blackstock, Dayong Tian, Xing-Fang LiIodinated disinfection byproducts
(I-DBPs) are highly toxic, but
few precursors of I-DBPs have been investigated. Tyrosine-containing
biomolecules are ubiquitous in surface water. Here we investigated
the formation of I-DBPs from the chloramination of seven tyrosyl dipeptides
(tyrosylglycine, tyrosylalanine, tyrosylvaline, tyrosylhistidine,
tyrosylglutamine, tyrosylglutamic acid, and tyrosylphenylalanine)
in the presence of potassium iodide. High resolution mass spectrometry
and tandem mass spectrometry (MS/MS) analyses of the benchtop reaction
solutions found that all seven precursors formed both I- and Cl-substituted
tyrosyl dipeptide products. Iodine substitutions occurred on the 3-
and 3,5-positions of the tyrosyl-phenol ring while chlorine substituted
on the free amino group. To reach the needed sensitivity to detect
iodinated tyrosyl dipeptides in authentic waters, we developed a high
performance liquid chromatography (HPLC)-MS/MS method with multiple
reaction monitoring mode and solid phase extraction. HPLC-MS/MS analysis
of tap and corresponding raw water samples, collected from three cities,
identified four iodinated peptides, 3-I-/3,5-di-I-Tyr-Ala and 3-I-/3,5-di-I-Tyr-Gly,
in the tap waters but not in the raw waters. The corresponding precursors,
Tyr-Ala and Tyr-Gly, were also detected in the same tap and raw water
samples. This study demonstrates that iodinated dipeptides exist as
DBPs in drinking water.