Ionic liquid-based aqueous two-phase extraction as a pretreatment strategy for the determination of 38 pharmaceuticals and personal care products in aquatic environments by HPLC-MS/MS

Abstract

The accurate determination of pharmaceuticals and personal care products (PPCPs) in wastewater is crucial for comprehensive environmental risk assessment and human exposure evaluation. Given the complex matrices of aqueous environmental samples, efficient sample preparation remains a critical challenge in analytical procedures. This study presents an ionic liquid-based aqueous two-phase system (IL-ATPS) extraction methodology used as a pretreatment step prior to high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) for the simultaneous determination of 38 PPCPs. A mechanistic investigation revealed that target analytes with more hydrogen-bonding sites and higher hydrogen-bond donor (HBD) capacity exhibited enhanced solubility in ILs. In addition, IL anions with stronger hydrogen-bond acceptor (HBA) capacity further improved the solubility of the 38 PPCPs. These findings indicate that hydrogen bonding between analytes and ILs likely played a critical role in the dissolution mechanism. The established IL-salt ATPS extraction method utilized a 15 mL aqueous sample, 0.2 g tetraethylammonium acetate ([N₂₂₂₂][OAc]), and 12 g K₂HPO₄, with a 1-minute vortex mixing. Compared with traditional solid phase extraction (SPE), this approach significantly reduced the sample volume from 1 L to 15 mL, avoided the use of volatile organic solvents, simplified the overall processing, and enabled rapid (<15 minutes) pretreatment. The method demonstrated excellent sensitivity with limits of detection (LODs) ranging from 0.00013 to 0.11 ng/mL. Method validation via standard addition experiments demonstrated satisfactory accuracy, yielding recoveries between 74.3 and 129.8 %. Precision was assessed using both intra-day and inter-day measurements. The intra-day relative standard deviations (RSDs) ranged from 0.7 % to 19.9 %, while the inter-day RSDs ranged from 1.4 % to 18.4 %, demonstrating that the method provides consistent and reproducible results under controlled laboratory conditions. These findings underscore the present IL-based ATPS extraction method, followed by HPLC-MS/MS analysis, as an eco-friendly, robust, and scalable approach for PPCPs monitoring in aqueous environmental samples, offering potential applications in environmental monitoring and risk assessment.