Preparation of magnetic zwitterionic covalent organic frameworks for rapid simultaneous extraction of hydrophilic and hydrophobic organophosphates from environmental waters coupled with UHPLC-MS/MS determination.

Organophosphate esters (OPEs) are a class of additive flame retardants that exhibit persistence, toxicity, and bioaccumulative potential. These compounds can persist in environmental media for extended periods and may enter the human body through multiple exposure pathways, thereby posing significant risks to human health. In this research, a novel analytical method for the simultaneous determination of trace amounts of 14 hydrophilic and hydrophobic OPEs (log Kow=1.53-8.90) in water samples is developed by using magnetic zwitterionic covalent organic framework (COF) based on magnetic solid-phase extraction prior to UHPLC-MS/MS analysis. Inspired by the amphiphilic molecular architecture of phospholipid bilayers, we rationally designed and synthesized a phosphoester-functionalized COF anchored onto magnetite nanoparticles (Fe3O4@P-ZCOF). The effects of various extraction parameters, including Fe3O4@P-ZCOF dosage, solution pH, extraction time, eluent type, elution duration, and ionic strength, on the extraction efficiency of the target analytes were systematically investigated. Under the optimized extraction conditions, 14 OPEs were successfully pretreated within only 6 min. The limits of detection (LOD, S/N = 3) for wastewater, reservoir water and tap water range from 0.01 to 1.50 ng/L, 0.01 to 1.00 ng/L and 0.01 to 2.00 ng/L, respectively. The method presents some merits such as quick and simple sample pretreatment procedure, and being able to simultaneously determine the hydrophilic and hydrophobic properties of OPEs. The method was successfully used to detect OPEs in the effluent and influent of 6 sewage treatment plants.