Liquid chromatography - high-resolution quadrupole time-of-flight mass spectrometry analysis of pesticides in French agricultural soils

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-of-flight 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 QTOF-MS. 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 mu g L-1) and high levels (12.5 to 400 mu g L-1) using labelled internal standards. The determination coefficient (R-2) 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 mu g kg(-1) and 10 mu g 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 mu g 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 g kg(-1) dw for triazines, 1.367 mu g kg(-1) dw for phenylureas and 7.638 mu g kg(-1) dw for emerging pesticides. DCPMU and epoxiconazole were detected in all the 40 soils.

Automated summary

Lack of control over the use of pesticides in agricultural soils in France. Developed a targeted method for analysis of pesticides in soils. Detected multiple pesticides in 40 soil samples, with DCPMU and epoxiconazole being detected in all soils.