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-MS(2)) 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 1.5mL of acetonitrile extract (disperser solvent), 125μL carbon tetrachloride (extraction solvent) and 10mL aqueous solution, the selected conditions. The enriched organic phase was evaporated, reconstituted with 50μL 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 C8 stationary phase. Detection limits in the 0.0015-0.0090ngg(-1) range were obtained. Insecticide concentrations ranging from 0.03 to 197ngg(-1), depending on the compound, were found in the soil samples analysed. The recovery values obtained by SLE-DLLME-LC-ESI-MS(2) for three spiked soils at three concentration levels varied between 87 and 114%, with RSDs of between 5.5 and 14%.