Simultaneous electrochemical detection of multiple heavy metal ions in milk based on silica-modified magnetic nanoparticles

A sensitive and simple analytical method integrated with Fe3O4@SiO2-based extraction with direct electrochemical detection was applied to individually and simultaneously analyze heavy metal ions, including Cd2+, Pb2+, Cu2+, and Hg2+. The Fe3O4@SiO2-based electrochemical sensor was developed through the mixture of heavy metal ions with Fe3O4@SiO2 after alkali treatment, which was modified onto the working electrode surface. The Fe3O4@SiO2 with negative charges after alkali treatment could easily interact with heavy metal ions with positive charges by electrostatic force. Under the optimized conditions, the developed analytical method could be applied to individually and simultaneously detect heavy metal ions with good sensitivity. The detection limits were all in the nanomolar range, and the recoveries ranged from 96.0 to 104.3% for heavy metal ions in milk. Therefore, the proposed analytical method exhibited great potential for quantitatively analyzing multiple heavy metal ions in milk.