Magnetic retrieval of an extractant: fast ultrasound-assisted emulsification liquid–liquid microextraction for the determination of polycyclic aromatic hydrocarbons in environmental water samples

Abstract

A novel two-step extraction technique combining ultrasound-assisted emulsification liquid–liquid microextraction with magnetic retrieval has been developed and applied to the analysis of six polycyclic aromatic hydrocarbons in environmental water samples coupled with high-performance liquid chromatography. The technique involves an initial extraction of the target analytes by ultrasound-assisted emulsification liquid–liquid microextraction into fine droplets of an organic extractant; and a retrieval and separation process of the organic phase from the aqueous solution with highly hydrophobic magnetic particles. In this way, the organic phase containing the analytes is the target of the magnetic retrieval step rather than the analytes directly. A noteworthy feature of the method is the introduction of highly hydrophobic magnetic particles with hierarchical structure for the magnetic retrieval of an extractant. Under the optimized conditions, good linearity ranging from 0.016 to 80 μg L⁻¹ was obtained in spiked water samples with correlation coefficients (R²) ranging from 0.9962 to 0.9998 and low limits of detection ranging from 2.0 to 19.5 ng L⁻¹. The proposed method has been validated in the analysis of real water samples with recoveries in the range of 75.4% to 110.5% and relative standard deviations of less than 9.9%.