Preparation, characterization, and application of chitosan-kaolin-based nanocomposite in magnetic solid-phase extraction of tetracycline in aqueous samples

A magnetic adsorbent based on chitosan-kaolin (Cs-k-Fe3O4) nanocomposite was synthesized by a one-pot co-precipitation method. The nanocomposite was used as an adsorbent in magnetic solid-phase extraction of tetracycline (TC) in wastewater and surface water. The Cs-k-Fe3O4 nanocomposite was characterized by the Fourier transform infrared spectrometer, X-ray powder diffractometer, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), and transmission electron microscope. The performance of Cs-k-Fe3O4 for extraction and pre-concentration of TC in wastewater was evaluated by investigating the effect of sample pH, extraction time, the mass of adsorbent, sample, and eluent volumes using a central composite design. The optimized extraction conditions were; 7, 60 mg, 30 mL, 15 min, and 2259 mu L for sample pH, mass of adsorbent, sample volume, extraction time, and eluent volume, respectively. A pre-concentrated TC was further analyzed using high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD). Under optimal conditions, the analytical method yielded good linearity for TC with a coefficient of determination (R-2) of 0.9928 and the limits of detection and quantitation of 0.21 and 0.63 mu g L-1, respectively. The method was validated using spike recovery experiments, and the percentage recoveries ranged from 89 to 103%, with intraday and interday relative standard deviations ranging between 0.6-2.7 and 1.0-2.0, respectively. The application of the analytical method in environmental analysis of TC resulted in the detection of the analyte in wastewater influent with a concentration of 2.92 mu g L-1, while the effluent levels were below the quantitation limit. Overall, the proposed analytical method proved to be efficient for the monitoring of TC in water.