title: Mass Spectrometry Identification of N-Chlorinated Dipeptides in Drinking Water.
abstract: We report the identification of N-chlorinated dipeptides as chlorination products in drinking water using complementary high-resolution quadrupole time-of-flight (QTOF) and quadrupole ion-trap mass spectrometry techniques. First, three model dipeptides, tyrosylglycine (Tyr-Gly), tyrosylalanine (Tyr-Ala), and phenylalanylglycine (Phe-Gly), reacted with sodium hypochlorite, and these reaction solutions were analyzed by QTOF. N-Cl-Tyr-Gly, N,N-di-Cl-Tyr-Gly, N-Cl-Phe-Gly, N,N-di-Cl-Phe-Gly, N-Cl-Tyr-Ala, and N,N-di-Cl-Tyr-Ala were identified as the major products based on accurate masses,35Cl/37Cl isotopic patterns, and MS/MS spectra. These identified N-chlorinated dipeptides were synthesized and found to be stable in water over 10 days except N,N-di-Cl-Phe-Gly. To enable sensitive detection of N-chlorinated dipeptides in authentic water, we developed a high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method with multiple reaction monitoring (MRM) mode. N-Cl-Tyr-Gly, N,N-di-Cl-Tyr-Gly, N-Cl-Phe-Gly, N-Cl-Tyr-Ala, and N,N-di-Cl-Tyr-Ala along with their corresponding dipeptides were detected in authentic tap water samples. The dipeptides were clearly detected in the raw water, but the N-chlorinated dipeptides were at background levels. These results suggest that the N-chlorinated dipeptides are produced by chlorination. This study has identified N-chlorinated dipeptides as new disinfection byproducts in drinking water. The strategy developed in this study can be used to identify chlorination products of other peptides in drinking water.
authors.affiliation: Division of Analytical and Environmental Toxicology, Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, University of Alberta , Edmonton, Alberta, Canada T6G 2G3.
authors.forename: Guang
authors.initials: G
authors.lastname: Huang
authors.affiliation: Division of Analytical and Environmental Toxicology, Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, University of Alberta , Edmonton, Alberta, Canada T6G 2G3.
authors.forename: Ping
authors.initials: P
authors.lastname: Jiang
authors.affiliation: Division of Analytical and Environmental Toxicology, Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, University of Alberta , Edmonton, Alberta, Canada T6G 2G3.
authors.forename: Xing-Fang
authors.identifier: 0000-0003-1844-7700
authors.initials: XF
authors.lastname: Li
mesh_terms: D004151:Dipeptides / Q000032:analysis*; D060766:Drinking Water / Q000737:chemistry*; D054879:Halogenation; D013058:Mass Spectrometry; D015394:Molecular Structure
chemical_list: D004151:Dipeptides; D060766:Drinking Water