Determinação multiclasse de resíduos de antimicrobianos em solo empregando QuEChERS modificado e UHPLC-MS/MS

Abstract

Global population growth has led to an increase in animal production, with intensive feeding of confined animals being widely exploited. Unchanged or metabolized veterinary drugs can be released into the environment through the urine and faeces of animals in pastures and aquaculture, or even indirectly through the use of contaminated manure in fertilization. The excessive and improper use of antimicrobials in animals contributes to the increased threat of antimicrobial resistance and the consequent absorption of these compounds into the soil. In addition to the damage caused to human and animal health, contamination by antimicrobials in the soil causes a decrease in microorganisms, as well as an imbalance in enzymatic activity, which compromises its fertility. Given the ecotoxicity of antimicrobials and potential adverse effects on human health, monitoring these compounds in the soil is essential. Therefore, the aim of this study was to develop and validate a method for the multiclass determination of antimicrobials in soil using Ultra-High Performance Liquid Chromatography coupled to Serial Mass Spectrometry (UHPLC-MS/MS) after a sample preparation step using a modified QuEChERS method. The sample preparation method consisted of a two-step sequential extraction of the antimicrobials from the soil with the prior addition of 0.1 mol L-1 Na2EDTA, followed by a mixture of acetonitrile containing 7% (v/v) formic acid and phosphate buffer (2:1, v/v). The extract was partitioned by adding 4 g of Na2SO4 and 1 g of NaCl, and the extract (1 mL) was cleaned by dispersive solid phase extraction (d-SPE) using 50 mg of C18 and 150 mg of anhydrous MgSO4. The extract was diluted in water before analysis by UHPLCMS/MS. In addition, the interaction time of the antimicrobials with the soil before performing the extraction, as well as the robustness were evaluated. The proposed method was successfully validated for 35 compounds. The tests were conducted using an external calibration curve, proving to be an effective and robust method. The antimicrobials showed linearity in the working range evaluated from 0.5 to 20 µg L-1 , with coefficients of determination greater than 0.99. The recoveries obtained ranged from 70 to 110% with a relative standard deviation ≤20%, and the method limit of quantification ranged from 8 to 16 μg kg-1 , while the limit of detection ranged from 2.4 to 4.8 μg kg-1 . Based on the results obtained, the use of modified QuEChERS associated with UHPLC-MS/MS enabled the determination of antimicrobials in soil with satisfactory selectivity and sensitivity for routine analysis.