Deciphering the Effects of Quenching on the Chemodiversity of Low- and Non-volatile Disinfection Byproducts in Drinking Source Water Using ESI(-)-FT-ICR MS.

Quenching is essential for terminating chlorination and preserving halogenated disinfection byproducts (X-DBPs) in disinfected waters. However, the effects of quenchers on the chemodiversity and stability of low- and non-volatile X-DBPs are still poorly understood. Four quenchers─sodium sulfite (SS), sodium thiosulfate (STS), ascorbic acid (AA), and 1,3,5-trimethoxybenzene (TMB)─were employed to elucidate their influences on the non-targeted analysis of X-DBPs using Fourier transform ion cyclotron resonance mass spectrometry under negative electrospray ionization mode (ESI(-)-FT-ICR MS). Compared with the insignificant difference in decomposed X-DBPs, the average number of additionally formed X-DBPs for AA was significantly lower than that for SS (31 ± 18 versus 67 ± 35) at their optimum doses. The decomposition and additional formation caused by three reductive quenchers on the characterization of X-DBPs and their precursors followed the order: AA < STS < SS. Moreover, TMB was recommended to quench residual chlorine for one hour at the quencher-to-residual chlorine molar ratio of 2.00 because of its advantages in avoiding the decomposition of redox-sensitive X-DBPs and additional formation of X-DBPs by ESI(-)-FT-ICR MS, while exhibiting insignificant impacts on the overall molecular characteristics of DOM. This study provides novel insights into the effects of quenching on the non-targeted analysis of X-DBPs.