Surfactant coated magnetic nanoparticle-based solid-phase extraction coupled with spectrophotometric detection for determination of ultra-trace amounts of indomethacin in biological fluids

A novel mixed hemimicelle-based solid-phase extraction method using cetyltrimethylammonium bromide (CTAB) adsorbed onto the surface of magnetic Fe3O4 nanoparticles was developed for extraction/preconcentration of ultra-trace amounts of indomethacin from biological fluids. Magnetic nanoparticles were synthesised via a simple chemical co-precipitation method and characterised by a transmission electron microscope, an X-ray diffractometer and Fourier transform infrared techniques. The method utilises the unique properties of Fe3O4 nanoparticles including high surface area and superparamagnetism causing rapid separation (<20 min) and low adsorbent usage (only 50 mg). A comprehensive study on the parameters affecting the adsorption efficiency such as the amount of CTAB, pH of the solution, desorption conditions, amount of Fe3O4 nanoparticles, extraction and preconcentration time, sample volume and ionic strength are presented. Under optimum conditions, the method's linearity was over a range of 25-450 ng ml(-1). The limit of detection of 8.6 ng ml(-1), an enrichment factor of 99 and the relative standard deviation (%RSD) of 1.9% (for a concentration of 50 ng ml(-1)) were obtained. The method was successfully applied to determine indomethacin in human plasma and urine samples. Good recoveries (89-102%) with low %RSD, (1.7-2.7%) were achieved.