Monitoring Pesticide Residues in Anuran Liver Tissue: A Proposal for the Sample Preparation Method

In this work, a miniaturized version of the QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was optimized, validated, and applied for extracting eight pesticide residues in anuran liver tissue samples. The extracts were quantified by high-performance liquid chromatography with diode array detection, and the detected residues in liver tissue samples were identified by tandem mass spectrometry-liquid chromatography. The optimized extraction method entailed the scale reduction of the QuEChERS method twenty times using 500 mg of liver tissue sample, 200 mg Mg₂SO₄, 50 mg NaCl, 1.5 mL of acetonitrile, and a mixture of 25 mg C₁₈ + 25 mg PSA (primary-secondary amine) as dispersive solid-phase extraction sorbent. The method was validated using liver tissue samples spiked at two levels of pesticide concentrations according to the SANTE/11312/2021 document. Recoveries ranged from 91-110% with a relative standard deviation < 20%. The method robustness assessed by the Steiner and Youden test resulted in recovery rate variations of less than 2% for all pesticides after deliberated changes in seven variables. The validated method was applied to 72 liver tissue samples from two anuran species, registering residues of some pesticides in 31 samples. The proposed method proved to be efficient, precise, and robust for determining pesticide residues in anuran liver tissues.

Keywords:
QuEChERS; HPLC; extraction; L. macrosternum ; Scinax x-signatus