Three Birds with One Fe₃O₄ Nanoparticle: Integration of Microwave Digestion, Solid Phase Extraction, and Magnetic Separation for Sensitive Determination of Arsenic and Antimony in Fish

An environmentally friendly and fast sample treatment approach that integrates accelerated microwave digestion (MWD), solid phase extraction, and magnetic separation into a single step was developed for the determination of arsenic and antimony in fish samples by using Fe₃O₄ magnetic nanoparticles (MNPs). Compared to conventional microwave digestion, the consumption of HNO₃ was reduced significantly to 12.5%, and the digestion time and temperature were substantially decreased to 6 min and 80 °C, respectively. This is largely attributed to Fe₃O₄ magnetic nanoparticles being a highly effective catalyst for rapid generation of oxidative radicals from H₂O₂, as well as an excellent absorber of microwave irradiation. Moreover, potential interferences from sample matrices were eliminated because the As and Sb species adsorbed on the nanoparticles were efficiently separated from the digests with a hand-held magnet prior to analysis. Limits of detection for arsenic and antimony were in the range of 0.01–0.06 μg g^–1 and 0.03–0.08 μg g^–1 by using hydride generation atomic fluorescence spectrometry, respectively, and further improved to 0.002–0.005 μg g^–1 and 0.005–0.01 μg g^–1 when inductively coupled plasma mass spectrometry was used as a detector. The precision of replicate measurements (n = 9) was better than 6% by analyzing 0.1 g test sample spiked with 1 μg g^–1 arsenic and antimony. The proposed method was validated by analysis of two certified reference materials (DORM-3 and DORM-4) with good recoveries (90%–106%).