Dispersive liquid-liquid microextraction for the determination of new generation pesticides in soils by liquid chromatography and tandem mass spectrometry

A sensitive method for the determination of five new generation pesticides (chlorantraniliprole, spirotetramat, spiromesifen, spirodiclofen and flubendiamide) in soil samples has been developed using liquid chromatography and tandem mass spectrometry (LC-MS2) with a triple-quadrupole in the multiple reaction monitoring mode. The target analytes are released from the solid matrix by single-phase extraction in acetonitrile (SLE), this organic phase being used as dispersant solvent in the dispersive liquid-liquid microextraction (DLLME) step. The different parameters affecting the extraction efficiency in DLLME were carefully studied, being 1.5 mL of acetonitrile extract (disperser solvent), 125 mu L carbon tetrachloride (extraction solvent) and 10 mL aqueous solution, the selected conditions. The enriched organic phase was evaporated, reconstituted with 50 mu L acetonitrile and injected into a liquid chromatograph with a mobile phase composed of acetonitrile and 0.1% (v/v) formic acid under gradient elution and a C-8 stationary phase. Detection limits in the 0.0015-0.0090 ng g(-1) range were obtained. Insecticide concentrations ranging from 0.03 to 197 ng g(-1), depending on the compound, were found in the soil samples analysed. The recovery values obtained by SLE-DLLME-LC-ESI-MS2 for three spiked soils at three concentration levels varied between 87 and 114%, with RSDs of between 5.5 and 14%. (C) 2015 Elsevier B.V. All rights reserved.