An iron oxide nanoparticle-phosphorylated cellulose nanofiber-graphene oxide composite for electrochemical...

This work presents the development, characterization, and partial analytical method validation of a non-enzymatic electrochemical sensor based on a nanocomposite comprising iron oxide magnetic nanoparticles (MNPs), phosphorylated cellulose nanofibers (pCNF), and graphene oxide (GO) for the determination of chloramphenicol (CAP) by square-wave adsorptive stripping voltammetry. The MNPs@pCNF-GO composite was synthesized and deposited onto a glassy carbon electrode (GCE) by drop-casting, forming an MNPs@pCNF-GO-modified GCE (MNPs@pCNF-GO-GCE). The successful formation and morphological, structural, interfacial, and magnetic properties of the magnetic nanocomposite were investigated using scanning transmission electron microscopy, X-ray diffraction, zeta potential analysis, and vibrating-sample magnetometry. Time-of-flight secondary ion mass spectrometry confirmed extensive coverage of the GCE surface with the MNPs@pCNF-GO layer. The influence of the drop-cast volume (V) of MNPs@pCNF-GO and dissolved oxygen on the electrochemical signal was investigated. A drop-cast volume V of 20 μL of MNPs@pCNF-GO dispersion on the GCE surface suppressed the oxygen reduction signal, eliminating the need for oxygen removal and enabling rapid analysis. The partial method validation was performed in 0.1 M phosphate buffer solution (pH = 6.5) after applying the Savitzky-Golay smoothing procedure. The experimentally determined limit of detection (LOD) and limit of quantification (LOQ) were 39.9 μg L^-1 and 79.7 μg L^-1, respectively. The determined linear concentration range was from the LOQ to 2336.4 μg L^-1 (R² ≥ 0.99). The method was deemed accurate and precise, with average recoveries of 98.8% (at the low concentration level of the linear concentration range) and 99.1% (at the middle concentration level of the linear concentration range) and relative standard deviations (RSD) of 5.3% and 7.9%, respectively. The repeatability and reproducibility of the method were also tested and confirmed, with RSD values of 4.7% and 6.1%, respectively. The applicability of the developed MNPs@pCNF-GO-GCE was successfully demonstrated for the analysis of tap water using the multiple standard addition method, confirming accurate and precise determination. An interference study showed that common cations and anions present in tap water do not significantly affect CAP determination.