A Dual-Readout Magnetic Nanoparticle-Based Enzyme Assay For The Sensitive Detection Of Hg(Ii) Ions In Drinking Water

Development of miniaturized sensitive techniques for the analysis of toxic mercury ions (Hg2+) in water is of immense interest due to public health concerns. A miniaturized colorimetric FeMNPs-AlOx probe was developed for rapid and selective detection of Hg2+ ions in drinking water with a significantly low limit of detection 0.1 ng L-1. A linear working range of detection of 0.5-100 ng L-1 for Hg2+ ions was achieved for 200 mu L assay volumes with 10 min analysis times. The sensing system comprises alcohol oxidase enzymes (AlOx) coupled to iron oxide magnetic nanoparticles (FeMNPs) (average particle size 40 nm) via silane cross-linkers. The activity of the sensing probe was quantified using methanol, horseradish peroxidase (HRP) enzyme, and O-phenylenediamine (OPD) as the colorimetric substrate. The developed sensing probe was tested for analysis in drinking water samples with recoveries of 93-100%. Selectivity toward Hg2+ ions was achieved using citrate buffer as a masking agent. Analysis of Hg2+ ions was also carried out in the presence of Certipur certified reference material (CRM) for a multielement solution (As, Be, Cd, Cr(VI), Hg, Ni, Pb, Se, Tl). The developed FeMNPs-AlOx sensing probe exhibited good storage stability (with 75% retention of original response) over one month when stored at 4 degrees C. The developed probe also provided clear visual detection of Hg2+ ions in drinking water samples via colorimetric sensing.