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MX was widely considered as one of the most important disinfection by-products (DPBs) and as the strong carcinogen in the chlorinated drinking water. Some model compounds which have been classified into four families were chlorinated at laboratory conditions. MX was produced only in the chlorinated substituted aromatic aldehydes and amino acids, while a possible new compound (COHC) was found in some substituted aromatic aldehydes, chlorinated substituted aromatic acids and phenols. Through the analysis of the peaks presented in mass spectrum, the composition and structure of the new compound are proposed as 2-chloro-5-oxo-3-hexene diacyl chloride (COHC) which could cause interference in the detection of MX. COHC has also been found in drinking water and extracted chlorinated fulvic acid solution from the sediment and water of Tai Lake, so it should bring about more attention.

Syringaldehyde (4-hydroxy-3,5-dimethoxybenzaldehyde) was chlorinated in the laboratory at different reaction time, temperature, pH and chlorine dose, and MX was determined and quantified by GC/MS. The finding suggests that the optimal chlorination conditions are as follows: temperature=298 K, pH=5, Cl:syrin. (mol:mol)=9:1. We also found that the formation of MX increased with the syringaldehyde concentration in a linear relationship. In addition, when syringaldehyde was chlorinated with a different chlorine dose in an alkaline condition, no MX was detected. This study will conduce to elucidating the kinetic process for the formation of MX from syringaldehyde and will be of great help for better control of MX in drinking water.

In this study, 21 suspected precursors of MX were chlorinated in laboratory condition. Only 8 of selected compounds syringaldehyde, acetosyringone, ferulic acid, 3-ethoxy-4-hydroxy-benzaldehyde, 3,4,5-trimethoxy-benzaldehyde, vanillin, tryptophan, and tyrosine were screened as precursors of MX. The yields of MX by chlorination of syringaldehyde are the highest and decreased with chlorine dose, but the yields of MX by the other 7 compounds increased with chlorine dose. It may be possible to elucidate the reaction mechanism for the formation of MX in light of the reaction of these screened precursors with chlorine.