Simultaneous LC-MS/MS determination of multi-class emerging contaminants in an orange plant system

Abstract

As freshwater supplies decline, agriculture is turning to alternative sources like recycled wastewater for irrigation. However, treated wastewater may still contain organic micropollutants (OMPs), which can contaminate soil, be absorbed by crops, and enter the food chain. This raises the need for analytical methods to reliable identify and quantify OMPs in vegetable and soil matrices at low concentrations. Additionally, advanced wastewater treatment methods are necessary to minimize OMPs in effluents from conventional wastewater treatment plants.

This study, part of a broader project on recycled wastewater for irrigating orange fields, focused on developing a modified QuEChERS method to determine 18 pesticides and 15 pharmaceuticals in soil, orange leaves and fruits. Compounds were quantified using liquid chromatography coupled to tandem mass spectrometry with a triple quadrupole. The methods were validated at two fortification levels (1–5 and 10–50 ng g⁻¹). Matrix effects were evaluated, showing a minimal impact in soil, but significant effects (> 20 %) in oranges and leaves, requiring matrix-matched calibration and/or isotopically labeled internal standards for accurate correction. The recoveries for most compounds were within 70–120 %, with relative standard deviations under 20 %, and limits of quantification ranged 1–5 ng g⁻¹.

In real samples, the insecticide acetamiprid was the most bioaccumulated contaminant, exceeding 20 ng g⁻¹ in leaves. Eleven pesticides were detected at concentrations below the limit of quantification, and the pharmaceutical atorvastatin was found in a soil sample.