Magnetic extraction and preconcentration of perfluorooctanoic acid in aqueous solutions using magnetic tea waste activated carbon

• Magnetic biochar adsorbent from tea waste was used for preconcentration of PFOA. • Incorporation of magnetic nanoparticles improved separation. • Low LOD and LOQ values in low ng/L levels, and a wide linear range were obtained. • The developed method yielded good spike recoveries ranging from 88.2% to 98.4 %. This study developed a method to determine perfluorooctanoic acid in real water samples using ultra-high performance liquid chromatography-electrospray-tandem mass spectrometry after dispersive magnetic solid phase extraction. The adsorbent used in dispersive magnetic solid phase extraction was tea waste activated carbon modified with magnetic nanoparticles. Successful synthesis of the adsorbent was confirmed by Fourier Transform infrared spectroscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The morphological and surface properties were investigated using scanning and transmission electron microscopy. Various experimental factors affecting the extraction and preconcentration efficiency were optimised using the design of experiments. Under the optimised conditions, the developed method had a wide linear range (39-5000 ng/L) with a correlation coefficient of 0.9915. The limit of detection was 11.7 ng/L, whereas the limit of quantification was 39.0 ng/L. The precision in terms of repeatability (intraday, n = 4 replicates) and reproducibility (interday, n = 3 days) expressed as %RSD were 2.40% and 3.10% respectively, which indicated that the developed method had good precision. The trueness of the developed method was investigated using a spike recovery test, and percentage recoveries ranged from 88.2% to 98.4 %. The magnetic activated carbon adsorbent could be reused up to 4 cycles. The developed method was successfully applied to detect perfluorooctanoic acid in three river water samples. Finally, the extent of greenness of the developed method was evaluated using six metric tools, and the findings showed that the method was environmentally friendly, cost-effective, highly practical and applicable.