Benzyl Functionalized Ionic Liquid as New Extraction Solvent of Dispersive Liquid-liquid Microextraction for Enrichment of Organophosphorus Pesticides and Aromatic Compounds

Abstract

Abstract A benzyl functionalized ionic liquid, 1-benzyl-3-methylimidazolium bis [(trifluoromethyl) sulfonyl] imide ([BeMIM][Tf 2 N]), was synthesized and used as an extraction solvent of dispersive liquid-liquid microextraction (DLLME) for enrichment and determination of 5 kinds of organophosphorus pesticides (phoxim, fenitrothion, chlorpyrifos, phorate and parathion) and 2 kinds of aromatic compounds (chloronaphthalene and anthracene) in environmental water samples by high-performance liquid chromatography (HPLC). [BeMIM][Tf 2 N] had higher extraction efficiency than 1-octyl-3-methylimidazolium bis [(trifluoromethyl)sulfonyl] imide and common organic solvents such as carbon tetrachloride and tetrachloroethylene. The extraction was performed using 40 μL of [BeMIM][Tf 2 N] as respective extraction solvent and 1 mL of methanol as dispersive solvent with centrifugal time of 5 min. Under the optimal conditions, the proposed method exhibited a good linearity for all analytes with correlation coefficients of 0.9994−0.9998. The precision, described as intra-day and inter-day relative standard deviations (RSDs) of five replicate experiments at three different concentrations of 10, 40 and 100 μg L −1 , was 1.1%–4.3% and 0.8%–4.8%, respectively. The limits of detection (LODs) were 0.01–1.0 µg L −1 ( S/N = 3). The developed method was convenient, rapid and applicable to detection of the analytes in real environmental water samples with satisfactory recovery of 82.7%–118.3% and RSDs of 0.7%–5.6%. Introduction of benzyl group into the imidazolium could considerably elevate the extraction efficiecny of the analytes due to enhanced π-π interaction between [BeMIM][Tf 2 N] and analytes. [BeMIM][Tf 2 N] was a satisfactory extraction solvent with a high enrichment factor of 339 and extraction efficiency of 81.4%. The partition coefficients of all analytes in [BeMIM][Tf 2 N]-DLLME system were determined and the extraction mechanism was discussed.