Liquid chromatography - high-resolution quadrupole time-of-flight mass spectrometry analysis of pesticides in French agricultural soils
Résumé
Agricultural soils are not controlled in France for the massive use of pesticides. The quadrupole mass spectrometer is used for targeted
analysis of a few dozen pesticides, while the high-resolution time-offlight quadrupole mass spectrometer (QTOF-MS) allows both targeted
and non-targeted analysis of hundreds of pesticides. In this study, a targeted method was developed in soils using pressurised-liquid
extraction (PLE) and liquid chromatography (LC) coupled with a QTOFMS. This method development was necessary to carry out next suspect
and non-target screening in soils and has been validated for triazines, phenylureas and emerging pesticides in soils. The internal calibration
of pesticides was validated for low levels (0.5 to 12.5 μg L−1) and high levels (12.5 to 400 μg L−1) using labelled internal standards. The determination
coefficient (R2) of calibration curve of each pesticide was greater than 0.99. Excepted DCPU and IPPU, the mean recoveries of
pesticides in five reference soils spiked at 40 μg kg−1 and 10 μg kg−1 were greater than 93.5% and 106.2%, and the variation coefficients
lower than 14.7% and 22.5%, respectively. So, multiplier factors were applied to the quantification results of DCPU and IPPU, respectively,
2.5 and 1.7 for correction. This validated method has been applied to a selection of 40 French soils of Centre-Val de Loire region. The limit of
quantification (LOQ) of pesticides varied between 0.005 and 0.175 μg kg−1 in soils. Seven pesticides were the most detected in soils.
Seventeen pesticides were detected between 10 and 50% of cases and very low detection frequencies (<10%) were found for 10 pesticides in
soils. The mean concentrations were 0.730 μg kg−1 dw for triazines, 1.367 μg kg−1 dw for phenylureas and 7.638 μg kg−1 dw for emerging
pesticides. DCPMU and epoxiconazole were detected in all the 40 soils.