In the present work, dispersive micro-solid phase extraction (D-μ-SPE) method using magnetic graphene oxide tert-butylamine (GO/Fe₃O₄/TBA) nanocomposite, as an efficient sorbent, was applied for determining 2,4-dichlorophenoxyacetic acid (2,4-D) in water and food samples. Detection was carried out using high-performance liquid chromatography (HPLC) instrument. Influential parameters of D-μ-SPE such as sorbent and its amount, elution solvent and its volume, adsorption and desorption times and pH of sample solution were investigated and optimized. Under the optimized conditions, limit of detection and quantitation values were 0.007 and 0.02 μg/mL, respectively. Recovery data for several real samples were obtained within the range of 88.0–94.0% with a relative standard deviation (RSD) less than 7.5%. The proposed method was successfully applied to quantitative determination of 2,4-D in several vegetables and water samples.

The present study explores the biosorption potential of Pleurotus ostreatus immobilized magnetic iron oxide nanoparticles for solid-phase extractions of Ni(II) and Pb(II) ions from the water and food samples. It was characterized using FTIR, FE-SEM/EDX before and after analyte ions biosorption. Important operational parameters including the effect of initial pH, the flow rate of the sample solution and volume, amount of biomass and support material, interfering ions, best eluent, column reusability were studied. The biosorption capacities of fungus immobilized iron oxide nanoparticles were found as 28.6 and 32.1 mg g⁻¹ for Ni(II) and Pb(II), respectively. The limit of detection (LOD) and limit of quantitation (LOQ) were achieved as 0.019 and 0.062 ng mL⁻¹ for Ni(II), 0.041 and 0.14 ng mL⁻¹ for Pb(II), respectively. The proposed method was validated by applying to certified reference materials and successfully applied for the preconcentrations of Ni(II) and Pb(II) ions from water and food samples by ICP-OES.

This study utilized reduced graphene oxide magnetic nanoparticles Fe₃O₄/rGO-MNP to preconcentrate two alkyl phenols, two organochlorine pesticides and one organophosphate pesticide from water and baby food samples for the determination by gas chromatography flame ionization detector (GC-FID). Parameters of the micro-solid phase extraction (μ-SPE) were fully optimized to boost the measurement signals of the analytes. Optimum extraction conditions were applied to aqueous standard solutions to validate the method. The limit of detection ranged between 0.48 and 2.4 μg/L, recording about 60–100 folds enhancement in detection power when compared directly with the detection limits of the instrument before preconcentration. The optimum method was applied to aqueous samples and spiked recovery tests produced satisfactory results. The baby food sample was treated with the QuEChERS standard method before applying the μ-SPE method. Matrix matching was used to overcome matrix interference to obtain approximately 1.0 % recovery results for all analytes spiked at different concentrations.