Evaluation of Two Fast and Easy Methods for Pesticide Residue Analysis in Fatty Food Matrixes

TLDR

The study evaluates and compares two rapid sample‑preparation methods for detecting 32 pesticide residues in fatty foods such as milk, eggs, and avocado. One method is a QuEChERS protocol that extracts 15 g of sample with acetonitrile containing 1 % acetic acid, followed by dispersive solid‑phase extraction with C18, PSA, and MgSO₄, while the second is a matrix solid‑phase dispersion approach that mixes 0.5 g of sample with C18 and Na₂SO₄, loads it onto a Florisil column, and elutes with MeCN; both extracts are analyzed by GC/MS and LC/MS/MS. Semi‑polar and polar pesticides were recovered at ~100 % by both methods (except basic pesticides were lost in MSPD), whereas non‑polar pesticide recoveries declined with increasing fat content, with hexachlorobenzene reaching only 27 % in 15 %‑fat avocado using QuEChERS.

Abstract

Abstract Two rapid methods of sample preparation and analysis of fatty foods (e.g., milk, eggs, and avocado) were evaluated and compared for 32 pesticide residues representing a wide range of physicochemical properties. One method, dubbed the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method for pesticide residue analysis, entailed extraction of 15 g sample with 15 mL acetonitrile (MeCN) containing 1% acetic acid followed by addition of 6 g anhydrous magnesium sulfate and 1.5 g sodium acetate. After centrifugation, 1 mL of the buffered MeCN extract underwent a cleanup step (in a technique known as dispersive solid-phase extraction) using 50 mg each of C18 and primary secondary amine sorbents plus 150 mg MgSO4. The second method incorporated a form of matrix solid-phase dispersion (MSPD), in which 0.5 g sample plus 2 g C18 and 2 g anhydrous sodium sulfate was mixed in a mortar and pestle and added above a 2 g Florisil column on a vacuum manifold. Then, 5 × 2 mL MeCN was used to elute the pesticide analytes from the sample into a collection tube, and the extract was concentrated to 0.5 mL by evaporation. Extracts in both methods were analyzed concurrently by gas chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry. The recoveries of semi-polar and polar pesticides were typically 100% in both methods (except that basic pesticides, such as thiabendazole and imazalil, were not recovered in the MSPD method), but recovery of nonpolar pesticides decreased as fat content of the sample increased. This trend was more pronounced in the QuEChERS method, in which case the most lipophilic analyte tested, hexachlorobenzene, gave 27 ± 1% recovery (n = 6) in avocado (15% fat) with a <10 ng/g limit of quantitation.