Application of core-shell magnetic metal-organic framework in developing dispersive micro solid phase extraction combined with dispersive liquid-liquid microextraction for the extraction and enrichment of some pesticides in orange blossom, Aloysia Citrodora, and fennel herbal infusions

This paper introduces an innovative technique for extracting pesticides from herbal infusions using a core-shell magnetic adsorbent (i.e., Cu-BTC@Fe₃O₄) where achieving a notable enrichment factor for the target pesticides by coupling with a dispersive liquid-liquid microextraction method. To validate the successful synthesis of the adsorbent, a range of analytical techniques were utilized including vibrating sample magnetometer, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray, and Brunauer-Emmett-Teller analyses. A vortex agitation and an external magnetic field were used during the extraction process to aid the analytes' desorption and adsorbent separation, respectively. Also, a mixture of iso-propanol and deionized water was used to desorb the analytes from the adsorbent surface. The resulting supernatant containing the desorbed pesticides was mixed with 1,2-dibromoethane as the extraction solvent and then injected into an aqueous medium. After centrifugation, 1 μL of the sedimented phase was introduced into the gas chromatograph system equipped with a flame ionization detector. The reliability of the proposed methodology was confirmed by obtaining low relative standard deviations (1.0–8.5 %), acceptable extraction recoveries (39–93 %), substantial enrichment factors (195–475), calibration curve linearity (r²=0.993–0.998), and significantly low limits of quantification (0.34–3.0 μg L⁻¹) and detection (1.1–9.9 μg L⁻¹). Absence of matrix effects with relative recovery values of 80–120 % for real samples, minimal use of the adsorbent and extraction solvent, a reduction in extraction time due to the elimination of two centrifugation steps (facilitated by an external magnetic field), and the use of environmentally friendly solvents collectively highlight the advantages and significant values of this approach.