Detection of Unknown Emerging Contaminants in Natural Water Using Tandem Mass Spectrometry

Recently, a great deal of concern has been given to the quality of drinking water. Lake Michigan is the drinking water source of Chicago area. It is very important that the quality of drinking water meets the standard setup by the EPA. However, there is a group of chemicals that are not being monitored regularly or are unknown to researchers and are the so-called emerging contaminants. So the objective of this study is to using tandem-mass spectrometry to detect and identify emerging contaminants. Water samples were obtained along a few locations along the Chicago River and Lake Michigan. By using the precursor ion of chlorine, those ions that contain chlorine were selected for further study. The accurate masses of selected precursor ions were obtained using the quadrupole-time-of-flight (QTOF). By searching the online databases, empirical formulas were tentatively assigned. Product ion spectrum and other research methods including synthesizing standards are utilized to assign the chemical structure unambiguously. 3,5-Dichloro-4-hydroxy-benzenesulfonic acid is the first unknown identified by this method. Further ions will be identified by the same research method. In a summary, tandem mass spectrometry coupled with high resolution mass spectrometry and online database searching is an effective method to identify known-unknowns. After the identification of these emerging contaminants, remedies should be proposed to degrade these contaminants