Development of an LC-MS-based method to study the fate of nanoencapsulated pesticides in soils and strawberry plant

Abstract

The increased production and use of nanopesticides will increase the likelihood of their exposure to humans and the environment. In order to properly evaluate their risk, it will be necessary to rigorously quantify their concentrations in major environmental compartments including water, soil and food. Due to major differences in the characteristics of their formulation, it is unclear whether analytical techniques that have been developed for conventional pesticides will allow quantification of the nano-forms. Therefore, it is necessary to develop and validate analytical techniques for the quantification of nanopesticides in foods and the environment. The goal of this study was to validate a method for analyzing the active ingredients of two pesticides with different physicochemical properties: azoxystrobin (AZOX, a fungicide, log Kow 3.7) and bifenthrin (BFT, an insecticide, log Kow 6.6) that were applied to agricultural soils, either as a conventional formulation or encapsulated in nanoparticles (either Allosperse® or porous hollow nSiO2). Pesticide-free strawberry plants (Fragaria × ananassa) and three different agricultural soils were spiked with the active ingredients (azoxystrobin and bifenthrin), in either conventional or nano formulations. A modified QuEChERS approach was used to extract the pesticides from the strawberry plants (roots, leaves and fruits) and a solvent extraction (1:2 acetonitrile) was employed for the soils. Samples were analyzed by liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry in order to determine method detection limits, recoveries, precision and matrix effects for both the “conventional” and nanoencapsulated pesticides. Results for the modified method indicated good recoveries and precision for the analysis of the nanoencapsulated pesticides from strawberries and agricultural soils, with recoveries ranging from 85 to 127% (AZOX) and 68–138% (BFT). The results indicated that the presence of the nanoencapsulants had significant effects on the efficiency of extraction and the quantification of the active ingredients. The modified analytical methods were successfully used to measure strawberry and soil samples from a field experiment, providing the means to explore the fate of nanoencapsulated pesticides in food and environmental matrices.