Magnetic nanoparticles solid phase extraction based on the formation of supramolecular mixed hemimicelle aggregates for the determination of naproxen in biological fluids using high-performance liquid chromatography-UV

A novel, fast, sensitive and practically solvent-free solid phase extraction method based on the adsorption of cetyltrimethylammonium bromide onto the surface of Fe₃O₄ nanoparticle adsorbent was developed for the quantitative determination of naproxen in biological fluids. The adsorbent was characterised by a transmission electron microscope, an X-ray diffractometer and Fourier transform infrared spectroscopy techniques. The main factors affecting the adsorption efficiency of the analyte such as the surfactant amount, pH value, desorption conditions, extraction and desorption time, sample volume, amount of Fe₃O₄ nanoparticles and ionic strength were evaluated and optimised. No clean-up steps were necessary for the determination of the drug in biological matrices because of the direct analysis of the eluate by liquid chromatography/UV, which is matrix-effect free. Under optimum conditions, naproxen was quantitatively determined and the linear range of the method was 0.1-700 ng ml^-1 with a correlation coefficient of 0.9993. An enrichment factor of 198 was obtained by extracting 200 ml of the sample solution. The detection limit was 0.01 ng ml^-1 and relative standard deviations (RSD %) for 20 and 150 ng ml^-1 were obtained as 2.9 and 2.3%, respectively. Finally, the proposed method was successfully applied to the determination of naproxen in human plasma and urine samples.