Zinc determination in aqueous samples using energy-dispersive X-ray fluorescence spectrometry after magnetic solid-phase microextraction using Fe₃O₄ nanoparticles

A novel analytical method for zinc (Zn) determination in aqueous samples was developed and validated using magnetic solid-phase microextraction (MSPME) combined with element detection <i>via</i> energy-dispersive X-ray fluorescence (EDXRF). Zn was extracted from aqueous samples using Fe₃O₄ nanoparticles impregnated with 1-(2-pyridylazo)-2-naphthol (PAN). Particle preparation involved two steps: synthesising magnetite(Fe₃O₄) particles and impregnating them with PAN. These impregnated nanoparticles were used to pre-concentrate and separate Zn before analytical quantification. The synthesised Fe₃O₄ particles were characterised as nanoparticles using several spectrometric techniques (X-ray powder diffraction (XRPD) and Raman spectroscopy). The efficiency of PAN impregnation was confirmed using Fourier Transform infrared spectroscopy (FT-IR). A single synthetic batch yielded sufficient material for 54 analyses. The validation showed limits of detection and quantification (LoD and LoQ, respectively) suitable for monitoring Zn levels in drinking water. Good alignment with a certified wastewater sample value was obtained with a mean recovery value of 96%. Moreover, a range of recoveries (106-109%) was obtained from spiked samples, indicating the trueness of the evaluation, and the precision was 8.0%. These results indicated that this analytical method was accurate and reliable for analysing these samples. In addition, EDXRF, a non-destructive technique, was applied to Zn quantification directly on the solid phase, making the proposed analytical method greener than classical atomic techniques such as flame atomic absorption spectroscopy (FAAS) or inductively coupled plasma atomic emission spectroscopy. This nanomaterial is postulated to be a solid-phase material applicable to MSPME procedures aimed at quantifying Zn in monitoring or remediation in environmental applications.