A new, simple, efficient and robust multi-residue method based on pressurised-liquid extraction of agricultural soils to analyze pesticides by liquid chromatography coupled with a high resolution quadrupole time-of-flight mass spectrometer

A new method for the analysis of pesticides in agricultural soils by using liquid chromatography coupled with a high-resolution quadrupole time-of-flight mass spectrometer (LC-QTOF-MS) has been developed. Twenty-four pesticides including herbicides, insecticides or fungicides have been studied. The linearity of the external calibration of the pesticides obtained from levels of concentration ranging from 0.010 to 400 µg/Lgives satisfactory results with the correlation coefficients higher than 0.99. The quantification limits of the equipment range from 0.010 to 1.250 µg/L and correspond to the lowest standard in the calibration range for which the residual deviation is less than 60%. An experimental design has been used to optimise the parameters of pressurised-liquid extraction (PLE) of pesticides in soils. The optimised conditions have been found by using methanol as extraction solvent at a temperature of 80°C, a pressure of 150 Bars and 2 extraction cycles of 5 minutes. The mean recoveries of pesticides (Mean) are higher than 72% with a relative standard deviation(RSD) less than 21%. These results demonstrate the good efficiency of PLE for the extraction of pesticides in agricultural soils of different nature. The LC-QTOF-MS is a sensitive, linear and robust instrument for the quantification of pesticides in unpurified soil extracts by external calibration. This analytical tool is not subjected to matrix effects of soil extracts.