Determination of pesticide residues in coconut tree trunks by modified QuEChERS method and ultra-high-performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry

A rapid and reliable method for the determination of 10 pesticide residues in coconut (Cocos nucifera L.) tree trunks after endotherapy treatments has been established. A modified QuEChERS (quick, easy, cheap, effective, rugged and safe) method, using an homogeneous sample slurry and acetate buffer, followed by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was developed and validated. Under the best extraction conditions, the average recoveries for all pesticides spiked at 40, 80 and 200 μg kg ranged from 70 to 93%, with RSD <10%. Intermediate precision expressed as RSD, ranged between 3 and 6% for all compounds. Calibration curves showed a wide linear range between 10.0 and 1000.0 μg kg for all compounds studied. Limit of quantification was established as 40.0 μg kg. The developed procedure was employed in the analysis of real coconut tree trunk samples obtained 45 h after pesticides application using endotherapy treatment. Concentrations of pesticides were between 44.7 ± 5 and 938.3 ± 20 μg kg. These results prove the translocation of pesticides in different heights, in the coconut tree trunk, from the application point. Imidacloprid presented the highest acropetal translocation and was found near the leaves at 61 ± 6 μg kg.