Box-Behnken Experimental Design for the Synthesis of Magnetite-Polypyrrole Composite for the Magnetic Solid Phase Extraction of Non-steroidal Anti-inflammatory Drug Residues

Abstract

A magnetite–polypyrrole composite adsorbent was synthesized and applied for the magnetic solid phase extraction of three non-steroidal anti-inflammatory drugs in aqueous solution and systematically investigated using Box–Behnken design. The synthesized composite adsorbent was characterized using Fourier-transform infrared spectroscopy, transmission electron microscopy, the Brunauer–Emmett–Teller method, vibrating sample magnetometry, and X-ray diffraction. The material was successfully modeled by Box–Behnken design (R2 = 0.94–0.98, p value: <0.001%) by monitoring the extraction efficiencies of naproxen, diclofenac sodium, and mefenamic acid. The analytes were determined using high-performance liquid chromatography with ultraviolet detection. The polymerization time was found to be the most significant factor, followed by amount of oxidant and monomer in the synthesis of the composite with a fixed Fe3O4 mass. Box–Behnken design was employed for the optimization of four parameters affecting the magnetic solid phase extraction: sample pH, salt addition, adsorption, and desorption time (R2 = 0.88–0.94). The optimized conditions for the procedure were validated, providing low detection limits (0.9–3.5 µg L−1) with good reproducibility (<7.16% relative standard deviation) and excellent recoveries (97.87–100.49%) for tap, river, and wastewater samples. The synthesized adsorbent demonstrated good adsorption efficiency for the simultaneous determination of the non-steroidal anti-inflammatory drug residues.