Rational design of an ionic liquid dispersive liquid–liquid micro-extraction method for the detection of organophosphorus pesticides

Abstract

In this study, a functionalized ionic liquid (IL), 3-methyl-1-(ethoxycarbonylmethyl) imidazolium bis(trifluoromethylsulfonyl)-imide ([MimCH₂COOCH₃][NTf₂]), was rationally designed and explored as an extraction solvent in dispersive liquid–liquid microextraction (DLLME) combined with ultra-high performance liquid chromatography (UHPLC) for the sensitive determination of organophosphorus pesticides (OPs). As π–π stacking interaction between the parent imidazolium cation core and the OPs is one of the most important factors, the proposed IL exhibited a high extraction efficiency. Moreover, during the DLLME process, a cloudy solution containing fine drops of [MimCH₂COOCH₃][NTf₂] allowed for a larger contact area between the OPs and the IL, which accelerated the mass transfer, and therefore the enrichment could be realized in a rapid fashion. Under the optimal extraction conditions, the developed method was successfully applied in the analysis of OPs in environmental water samples with a high enrichment factor (more than 400), good recovery and reproducibility.