Studies On Disinfection By-Products From Histidine In Chlorinated And Chloraminated Water

Disinfection blocks the spread of pathogens from drinking water to humans,and provides an important guarantee for human health and safety.Nowadays,chlorination and chloramination are the two commonly used drinking water disinfection methods.In the disinfection process,the disinfectant will inevitably react with the organic compounds in water and generate disinfection by-products(DBPs),which may be harmful to human beings.As the basic unit of protein,amino acids are ubiquitous in water,and also a kind of important organic precursor to form DBPs.Among them,histidine contains an imidazole ring and three N atoms,and nitrogen-containing compounds are prone to biological activity including toxicity.Therefore,histidine is very likely to generate harmful DBPs to human health during the water disinfection process.So it is crucial to study the chlorination and chloramination DBPs from histidine.In this paper,the DBPs from-histidine in different chlorination and chloramination disinfection reaction systems were studied by liquid chromatography couple with mass spectrometry(LC-MS).An ultra high performance liquid chromatography couple with quadrupole time of flight tandem high-resolution mass spectrometry(UHPLC-Q-TOF HRMS)method was established for the detection of the DBPs from histidine,and an ultra high performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry with dynamic multiple reaction monitoring(UHPLC-QQQ MS/MS-dMRM)method was also established to monitor the stabilities of the DBPs.A solid phase extraction(SPE)coupled with UHPLC-QQQ MS/MS-dMRM method was employed to determine the presence of histidine and the DBPs in authentic water.A UHPLC-QQQ MS/MS quantitative analysis method was established to study the chloramination reaction kinetics of histidine.Twenty-one chlorinated DBPs from histidine were detected.The molecular formulas of the DBPs were determined and their structures were deduced according to the exact molecular weight and MS/MS spectra.One of them was verified as 4(5)-nitrile imidazole by standard substances,and the other DBPs were alcohols,acids,nitriles,aldehydes,amides and chlorinated compounds containing imidazole ring,as well as some imidazole ring-opening chain compounds.The stabilities of the chlorinated DBPs were studied for 14 days in different disinfection reaction systems.Eight chloraminated DBPs from histidine were found.They were alcohols,acids,nitriles,aldehydes,amides and chlorinated compounds containing imidazole ring.Four of them were also chlorinated DBPs of histidine.Similarly,the stabilities of the chloraminated DBPs were also studied for 14 days in different chloramination reaction systems.Histidine and 6 DBPs were detected in authentic water.Histidine existed in various types of water.DBP-131,DBP-108-S and DBP-142.01 could be determined to come from the process of drinking water disinfection,while DBP-141,DBP-129 and DBP-157 were produced not only in the disinfection process,but also from other sources.The quasi-first-order reaction rate constants of histidine chloramination disinfection reaction at 4℃,13℃,22℃,31℃ and 40℃ were measured.The corresponding activation energy was calculated to be 60.463 kJ/mol according to the Arrhenius Equation.It provided methods and ideas for the study of the DBPs from other amino acids.Meanwhile,histidine and its 6 DBPs were detected from authentic drinking water.It was of great significance for the further toxicological study and the establishment of drinking water quality standards.