High-performance NiFe₂O₄/poly-L-cysteine nanocomposite for efficient detection of heavy metals in food samples

Nickel ferrite (NiFe₂O₄)-based poly-L-cysteine (PLC)-functionalized nanocomposite (NiFe₂O₄/PLC-NC) is a promising material for detecting toxic heavy metals (HMs), including Cd, Co, Ni, and Pb, in milk samples. In the current investigation, nickel ferrite nanoparticles (NiFe₂O₄-NPs) were synthesized via a sol-gel method and subsequently functionalized with PLC to obtain NiFe₂O₄/PLC-NC. The NiFe₂O₄/PLC-NC was characterized through various analytical techniques, including Fourier-transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy, revealing its optimal structure and surface properties. The synthesized NiFe₂O₄/PLC-NC was employed as an adsorbent to detect HMs in milk samples using a solid-phase extraction-based flame atomic absorption spectrometry method. The experimental results indicated that the adsorption capacity of NiFe₂O₄/PLC-NC was significantly affected by pH, adsorbent dosage, sample volume, and eluent type. The developed NiFe₂O₄/PLC-NC-based SPE method exhibited excellent sensitivity and accuracy, with detection limits of 0.0101 μg L^-1 for Cd, 0.0236 μg L^-1 for Co, 0.0350 μg L^-1 for Ni, and 0.0051 μg L^-1 for Pb. The NiFe₂O₄/PLC-NC-based SPE method was validated using certified reference material and real milk samples, demonstrating high analytical accuracy with recoveries exceeding 90% and relative standard deviations below 3.0%. These results confirm that the developed sorbent provides a reliable and efficient platform for the simultaneous determination of HMs in milk samples.