This research, aimed to synthesis and functionalize of Fe3O4 magnetic nanoparticles (MNPs) using dialdehyde starch and modifying with arginine amino acid. The resulting MNPs were characterized by Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscope (SEM) and Vibrating sample magnetometer (VSM). Synthesized MNPs were developed for preconcentration and determination of diclofenac in biological samples by UV- Vis Spectrophotometry. A Plackett–Burman experimental design was

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... used to evaluate the influence of effective parameters. Significant parameters were further optimized by Central Composite Design (CCD). Sample volume, pH and salting effect had a main effect on extraction of diclofenac by the proposed method. Under the optimized conditions, the detection limit (3Sb, n = 7) was found to be 0.039 µg ml− 1.The calibration curve showed dynamic linear 0.05-10 µg ml− 1 with correlation coefficients (R2) of 0.987. The enrichment factor was found to be 148. The proposed method showed good results for preconcentration and determination of diclofenac in serum and pharmaceutical samples.