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

International audienceBackground: The latest generation of liquid chromatograph coupled to high-resolution quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) now competes with quadrupole tandem spectrometers (LC-MS-MS) in terms of sensitivity and speed. In addition, it is possible to obtain additional information retrospectively on the organic composition of the analyzed soil. Due to the exponential increase of the storage capacities of computer hard drives and the speed of electronic processing of computer data, it is all the more possible to recover all of the data generated during the analysis of a soil extract.Objective: The LC-QTOF-MS currently has an essential and primordial advantage; which is the entire transmission of the ions produced in the ionization source towards the mass spectrometer. This original feature opens the way to a probable full exploration of the organic composition of the soils.Methods: 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.Results: 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/L gives 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 optimize the parameters of pressurized-liquid extraction (PLE) of pesticides in soils. The optimized 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 soils extracts by external calibration. This analytical tool is not subjected to matrix effects of soil extracts