Magnetic dispersive micro-solid-phase extraction integrated with hollow fiber liquid-phase microextraction for preconcentration of trace amounts of chlorpyrifos pesticide in aqueous samples

In the present study, the integration of magnetic dispersive micro-solid-phase extraction (MD-µSPE) with hollow fiber liquid-phase microextraction (HF-LPME) prior to gas chromatography–mass spectrometry (GC/MS) was developed to preconcentrate and determine trace amounts of chlorpyrifos pesticide. Azolla filiculoides fern biomass was loaded by magnetite nanoparticles to prepare magnetic adsorbent (azolla@Fe₃O₄). The structural characteristics of the produced magnetic nanocomposites (MNCs) were investigated by FESEM, TEM, VSM, FTIR, EDX, and XRD methods. In the proposed MD-µSPE/HF-LPME method, the adsorption/desorption variables in MD-µSPE step were optimized by Taguchi fractional factorial design. After chlorpyrifos adsorption in the optimized condition of MD-µSPE (V_sample = 50 mL, contact time = 15 min, solution pH = 3, adsorbent mass = 0.05 g, ionic strength = 0.01 mol L⁻¹, and eluent type = ethanol), 2.0 mL of the desorbed ethanolic solution was added to 16 mL of 10% (w/v) NaCl aqueous solution for the next HF-LPME method and the final analysis was performed by GC/MS. The developed method showed a limit of detection of 0.05 μg L⁻¹, a limit of quantification of 0.5 μg L⁻¹, a dynamic linear range of 0.5–1000.0 μg L⁻¹, preconcentration factors between 700 and 1050, and a repeatability (RSD%) of 6.9%. The suitability of the MD-µSPE/HF-LPME method was confirmed by measuring chlorpyrifos in real samples with relative recoveries in the range of 97.0–108.5%. The results showed good accuracy and precision of the developed MD-µSPE/HF-LPME method for the preconcentration and determination of trace amounts of chlorpyrifos in the aqueous samples.