Simultaneous Preconcentration and Determination of Co(II) and Cr(III) in Processed Meat Samples Using MgFe₂O₄@Bentonite Nanocomposite Magnetic Solid-Phase Extraction Coupled with FAAS

A nanocomposite adsorbent was prepared using magnesium ferrite and bentonite. The synthesized magnesium ferrite-bentonite nanocomposite exhibited selective extraction of cobalt and chromium without the need for a chelating agent. A micro-injection system attached to a flame atomic absorption spectrometry instrument was used to exploit the preconcentration capability of the established method. To optimize effective extraction of cobalt and chromium ions, several parameters were optimized, including sample pH, sample solution volume, eluent volume, adsorbent amount, and adsorption and desorption times. Under optimal conditions, the preconcentration factor was 50. The calibration curves were linear over the calibration range of 0.0–10.0 µg L−1 with coefficients of determination greater than 0.995 for all analytes. The limits of detection and quantification were 0.12 and 0.37 µg L−1 for Co(II) and 0.08 and 0.24 µg L−1 for Cr(III), respectively. The recoveries ranged from 90% to 108.7%, with relative standard deviations ranging from 1.2% to 4.0%, indicating good precision of the method. The magnetic solid-phase extraction method was successfully applied to food samples, enabling the determination of metal ion levels in chicken, beef, turkey, and tuna.