In-syringe dispersive liquid-liquid microextraction vs. solid phase extraction: A comparative analysis for the liquid chromatographic determination of three neonicotinoids in cotyledons

Abstract

A novel extraction strategy for the determination of imidacloprid, thiamethoxam and clothianidin in soy cotyledons by liquid chromatography was developed based on the implementation of an in-syringe-dispersive liquid-liquid microextraction system, optimized through successive experimental designs. First, a fractional factorial design was built to screen the influence of five experimental factors: a) aqueous solution (water or ethylenediaminetetraacetic acid 0.20 mol L?1); b) type of solvent (methanol or acetonitrile); c) use of salt (yes or no) for the adjustment of the ionic strength; d) homogenization method (vortex or sonication); and e) extractant solvent (toluene or ethyl acetate). Afterwards, in order to build a response surface model, a central composite design was implemented considering the influencing factors. For the in-syringe-dispersive liquid-liquid microextraction system, optimal conditions resulted in 1140 µL of acetonitrile, 583 µL of ethyl acetate and three successive extractions. Finally, due to fact that the system involves an evaporation step, a simplex-lattice mixture design was built. The optimum composition of the resuspension solution was methanol:water (60:40 v/v). The developed method was compared with a previously reported solid phase extraction methodology taken as reference method. Higher recovery percentages were achieved with the novel procedure, i.e. in the range of 69.5 to 74.2%, for the three considered analytes.