Identification Of The Disinfection By-products From The Chlorinated Nicotine And Anabasine

The aim of disinfection of drinking water is to kill the pathogen microorganisms and stop the water born disease.However,the disinfectants also react with the dissolved organic compounds to generate disinfection by-products(DBPs).Some of these DBPs such as THMs and HAAs have been confirmed as carcinogen in animal toxicity tests,and were regulated in many countries.Currently,the identified DBPs only contribute a minor portion of the total estimated DBPs.So,besides to continue the toxicity study of the identified DBPs,the identification of unknown DBPs is also a fundamental work to further improve the drinking water quality.Recently years,owning to the wide application of high resolution mass spectrometry(HRMS),the progress of identification of new DBPs has been greatly accelerated.However,the identified new DPBs in recent years is still very limited because of the complexity of the structure,low concentration and lack of versatile identification approaches.So,it is essential to develop an efficient and versatile analytical method for DBPs identification.In this dissertation,a new analytical method based on solid phase extraction(SPE)and liquid chromatography-tandem high resolution mass spectrometry(HPLC-HRMS/MS)was developed,which was able to detect the pollutants at less than 1 ng/L.Using this method,a screen analysis was performed for the raw waters,which were collected from local water treatment plants.By comparing the high accuracy of the mass to charge ratio(m/z,< 2 ppm)with the theoretical m/z of the pollutants,the suspect targets were selected,and then verified by their corresponding standards.The screen range covered the pesticides,herbicides and antibiotics.After screen,several pollutants including tebuconazole,carbendazim and nicotine were found in these water samples.The conventional water treatment procedures such as coagulation or sedimentation have little effect on the removal of these small molecular pollutants.So these pollutants will sneak into the water distribution system and react with the disinfectants to generate DBPs.To study these DBPs,a simulated lab chlorination was performed using the nicotine as precursor and the samples from different reaction time intervals were analysis by HPLC-HRMS/MS.To ensure the new products were generated from the nicotine,an isotope standard nicotine-D4 was applied in chlorination in parallel.All the products with considerable intensity and isotopic tags were considered as the DBPs.By performing the targeted MS2 screen,the product ions of each peak were obtained.With the assistance of the isotopic tag and the high accuracy of the m/z,8 DBPs including nicotinic acid and cotinine were identified.To further exhibit the applicability of this identification approach,anabasine which is an isomer of nicotine,was selected as the precursor for chlorination,and 6 DBPs were identified using the same approach.The next step of this work is to analyze large numbers of samples to confirm the existence and occurance of these newly identified DBPs.