Studies On Disinfection By-Products Of Lysine In Chlorinated And Chloraminated Water

Drinking water disinfection is an important barrier against the spread of pathogenic microorganisms and a critical step in the production of safe drinking water.Chlorination or chloramination is the most common drinking water disinfection technology at present.During the disinfection process,the organic matter will inevitably react with disinfectants in water and form complex and diverse disinfection by-products（DBPs）,which potentially threatens human health.As the main components of dissolved organic nitrogen in water,amino acids are an important class of organic precursor compounds that lead to the formation of DBPs,and they are prone to form highly toxic nitrogenous DBPs（N-DBPs）.In this paper,lysine was selected as the precursor compound.We studied the chlorinated and chloraminated DBPs from lysine by using ultra-high performance liquid chromatography couple with quadrupole time-of-flight mass spectrometry（UHPLCQ-TOF HRMS）.On this basis,ultra-high performance liquid chromatography couple with triple quadrupole tandem mass spectrometry（UHPLC-QQQ MS/MS）was used to monitor the stabilities of DBPs and studied the chlorination reaction kinetics of lysine:Firstly,a UHPLC-Q-TOF HRMS method for the analysis of DBPs from lysine was established and optimized.A total of twenty-six chlorinated DBPs from lysine were detected,and their structures were deduced based on precise molecular weights and fragments of MS/MS.These chlorinated DBPs were carboxylic acids,aldehydes,ketones,imines,lactams,lysine-coupled compounds,chlorinated compounds and so on,among which twenty-one were discovered for the first time.Furthermore,the UHPLC-QQQ MS/MS-dMRM method for monitoring the stability of these DBPs was established and optimized.Then the stability of them in disinfection reaction system with different molar ratios of lysine and NaCIO was further studied.Secondly,sixteen DBPs of lysine were found and deduced in the chloraminated water by using the same UHPLC-Q-TOF HRMS analysis method.These chloraminated DBPs were carboxylic acids,aldehydes,ketones,imines,lysine-coupled compounds,chlorinated compounds and so on.Eleven of them had the same structure as chlorinated DBPs,and twelve were discovered for the first time.Similarly,the UHPLC-QQQ MS/MS-dMRM method was established and optimized for monitoring the stability of these DBPs,and the stability of chloraminated DBPs in disinfection reaction system with different molar ratios of lysine and NH₂CI was further studied.Finally,we established and optimized a UHPLC-QQQ MS/MS quantitative analysis method for lysine.Based on this method,the pseudo-first-order kinetic constants of the chloramination disinfection reaction of lysine at 40,31,22,13,and 4℃ were determined.The apparent activation energy of the disinfection reaction was calculated to be 52.4206 kJ/mol according to Arrhenius Equation.Our work not only provides ideas and methods for the study of DBPs from amino acid,but also enriches the types of DBPs in drinking water.In addition,it provides a basis for the formulation of drinking water quality standards.