Application Of Target Screening And Non-target Screening In Identification Of Poisonous Chemical Factors In Aquatic Environment

With the rapid development of society and the intensification of human activities,a large number of synthetic chemicals enter the environmental water body and pose serious threat to human health and the survival of aquatic organisms.Thus it is essential to screen pollutants in water body on a large scale.In this paper,a mixed standard solution containing 533 kinds of standard compounds which are very likely to enter the waterbody was prepared,covering commonly used medicines,pesticides,veterinary drugs,food additives,surfactants,industrial raw materials,etc.UPLC/ESI-Q-TOF-MS was used for simultaneous analysis of these compounds and establishment of a screening list for target screening.The final list contains 248 compounds in positive ion model and 23 compounds in negative ion model.Seven water samples were collected from a river near a pharmaceutical zone and analyzed with UPLC/ESI-Q-TOF-MS.In the following target screening for the seven water samples,24 compounds in total were identified in positive ion mode,most of them(17)are pharmaceuticals.No compound was found in the water samples in negative ion mode.The number of compounds detected were 24,24,24,21,21 and 20 at the seven sampling sites 1-7,respectively.In non-target screening,the ion peaks identified in the water samples were classified as four levels according to a reported criteria.A total of 374 ion peaks were found,including 6 peaks at level-2,3 peaks at level-3,39 peaks at level-4 and 326 peaks at level-5.There are many kinds of pollutants in the environment.The traditional analysis for water quality usually determines the concentration of only a few certain kinds of pollutants.Such approaches cannot reflect not only the real status of contamination,but also the toxicological characteristics in aquatic environment.In contrary,biological assay can indicates comprehensive biological effects of all pollutants in aquatic environment and therefore has been widely used to evaluate the toxic characteristics of environmental water in recent years.In biological assay for water samples,zebrafish is widely used as a model organism.While the water samples were analyzed by high resolution mass spectrometry,their toxicities were also tested on zebrafish.It was found that exposure to the water samples lead to death of zebrafish.The death rates varied among the sampling sites.The presence of certain compounds in the water are speculated to result in the death of zebrafish.The relationship between the concentrations(or intensities)of all compounds(or peaks)detected in the water samples with the death rates of zebrafish in the exposure experiment was investigated to disclose the possible contributors to the death of zebrafish.Among all 398 compounds(or peaks)of data including target screening compounds and non-target screening compounds,189 peaks presented positive correlation(b>0),including 1 peak at level-2,2 peaks at level-3,11 peaks at level-4 and 175 peaks at level-5.The 24 compounds identified by target screening were not positively correlated with the death rates of zebrafish,suggesting that these compounds might not be the contributors to the death of zebrafish.Among all peaks with positive correlation with the death rates of zebrafish,all of the top 20 peaks with the strongest correlation were peaks at level-5.These 20 peaks may be the toxic contributors of zebrafish mortality,which needs to be further identified.