Quantitative screening of pesticides and their metabolites in human matrices: Are we ready to switch to high resolution mass spectrometry?

Abstract

Despite increasing debates about their potential side effects on human health, data on the risks and impacts associated with pesticides is scarce and fragmented. There is a need for analytical tools for the measurement of most pesticides and/or their metabolites to which the population might be exposed. In this study, we present both untargeted and targeted Liquid Chromatography High Resolution Mass Spectrometry (LC-HRMS) screenings, suitable for the determination of pesticides in serum. We included 205 pesticides and metabolites of interest, comprising among others carbamates, dithiocarbamates, neonicotinoids, organochlorines, organophosphates and pyrethroids. A QuEChERS salt extraction was applied and chromatographic separation was performed in a biphenyl 2.7 μm (100 × 2.1 mm I.D.) column. For the HRMS acquisition, a Q-TOF (LCMS-9030®, Shimadzu) was used. Data was acquired either with an untargeted (Data independant acquisition, DIA), or targeted acquisition mode (HR-MS/MS). For each molecule, we determined the limit of detection (LOD) in a calibration range between 0.05 and 10 ng/mL. The procedure was applied to 62 patient serum samples. Results were then compared with those of a classical Multiple reaction Monitoring (MRM) LC-MS/MS screening method based on a low resolution acquisition (triple quadrupole; LCMS-8060®, Shimadzu). Six calibration curves (on 6 different days) revealed that about 99% of the compounds exhibited a LOD≤5 ng/mL for both targeted and untargeted screenings. For about 2 thirds of the molecules (66% and 68%, respectively), LOD was ≤0.5 ng/mL. For about one quarter of them (22% and 26%, respectively) LOD≤0.1 ng/mL. Out of the 62 serum samples, 79 compounds (22 different pesticides and metabolites) were detected by LC-HRMS. At very low LOD (<0.05 ng/mL), only 7 additional compounds could be detected using the low resolution approach. We developed highly sensitive LC-HRMS screening methods allowing the detection of a large panel of pesticides considered responsible for environmental and occupational exposure. Some compounds however remain inaccessible to LC and require GC analysis demonstrating the need to combine analytical techniques to gain a better understanding of population exposure to pesticides.