Dispersive solid phase extraction of perfluorooctanoic acid from wastewater using chromium-doped CoFe layered double hydroxide for determination by LC-MS/MS

Polyfluoroalkyl substances (PFAS) are persistently dangerous substances in the environment, threatening human health even in very low concentrations. This work introduced a dispersive solid phase extraction (DSPE) based on Cr-doped CoFe layered double hydroxide (LDH), which was used as the extraction phase for the effective removal of perfluorooctanoic acid (PFOA) from wastewater samples. Cr-doped CoFe LDH was synthesized using the facile co-precipitation method. Successful partial substitution of Fe³⁺ by Cr³⁺ cations in the crystalline lattice of CoFe LDH was affirmed by energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and elemental dot-mapping analysis. Layered morphology was observed for both bare and Cr-doped CoFe LDH in scanning and transmission electron microscopy images. The influence of diverse parameters, including sorbent mass, eluent solvent type, volume of eluent, agitation mode, adsorption time, and pH, was assessed on the extraction of PFOA by Cr-doped CoFe LDH. The experimental data from the effective DSPE followed by liquid chromatography–tandem mass spectrometry exhibited a low limit of detection of 0.03 µg/L, broad linear range (0.1–300 µg/L and R² ≥ 0.997), and good repeatability (6.7 %, n = 5 intraday) for the enrichment and determination of PFOA in wastewater samples.