Solid-Phase Reactivity-Directed Microextraction Analysis for Identifying Unknown Toxic Disinfection Byproducts

The majority of disinfection byproducts (DBPs) remain unknown and may pose toxic risks. By mimicking the molecular interactions of toxicants with biomolecules, we developed a solid-phase microextraction (SPME) reactivity-directed analysis method for identifying unknown toxic DBPs. The probe 4-mercaptophenylboronic acid (MPA) was covalently immobilized onto the SPME fiber coating through cis-diol bonding. After the capture of potentially toxic DBPs through thiol reactions, the pH-responsive cleavage of boronate ester allowed for release of the MPA-DBP adducts. The boron isotope pattern (1:4) and characteristic fragments derived from the MPA moiety allowed for efficient prioritization of the adducts. Compared to the current homogeneous approach using liquid extracts, this heterogeneous method exhibited the advantages of biomimetic toxicity focus, effective pretreatment, and enhanced detection performance. The application in chlorinated simulated source water discovered 30 DBP-MPA adducts, in which the molecular structures of seven adducts, i.e., seven DBPs, were identified, including a known DBP chloroacetic acid and six newly found DBPs. Two of them were confirmed as 1-penten-3-one and methacrolein by using authentic standards. The toxicity and health risks of newly found DBPs were predicted using computational tools, indicating their toxicity contributions in disinfected waters. This study represents an important advance in the qualitative methodology for identifying unknown toxic DBPs.