Solvent demulsification-dispersive liquid-liquid microextraction based on solidification of floating organic drop coupled with ultra-high-performance liquid chromatography-tandem mass spectrometry for simultaneous determination of 13 organophosphate esters in aqueous samples

This study developed a novel method for the determination of 13 organophosphate esters (OPEs) in aqueous samples through the optimization of solvent demulsification-dispersive liquid-liquid microextraction based on solidification of floating organic drop procedure coupled with ultra-high-performance liquid chromatography-tandem mass spectrometry. The proposed method was rapid and accurate and could be used in field applications. Under the most suitable conditions, the limit of detection and limit of quantification ranged from 0.16 ng/L to 20.0 ng/L and from 0.55 ng/L to 66.7 ng/L, respectively. The enrichment factors (EFs) ranged from 30 to 46. The relative standard deviations were less than 15%. The spiked recoveries ranged between 68.2% and 97.7% in the analysis of actual aqueous samples. The proposed method was convenient, environment friendly, and time and solvent saving and could be used in field applications compared with other methods. Various concentrations and types of OPEs were detected in tap water, river water, and effluent of sewage treatment plant. Effluent samples had the highest detected levels and types of OPEs.