Visual test of subparts per billion-level copper(ii) by Fe3O4 magnetic nanoparticle-based solid phase extraction coupled with a functionalized gold nanoparticle probe

Abstract

By combining Fe₃O₄ magnetic nanoparticle-based solid phase extraction with a gold nanoparticle-based visual test, a novel method was developed for the field assay of Cu(II) in environmental water at subparts per billion-levels within 30 min. When a 200 mL water sample was treated with 12.5 mg L⁻¹ Fe₃O₄ nanoparticles by the proposed procedure, the detection limit with the naked eye was 0.2 μg L⁻¹ Cu(II). The proposed method is very specific to Cu(II), with tolerance against at least 100-fold amounts of other environmentally relevant metal ions except for Hg(II) (25-fold), and was successfully applied to the detection of trace Cu(II) in tap water, river water, and treated wastewater, and results agreed well with that determined by inductively coupled plasma-mass spectrometry (ICP-MS).