Gold-nanoparticle-based graphite furnace atomic absorption spectrometry amplification and magnetic separation method for sensitive detection of mercuric ions.

We have developed a sensitive gold-nanoparticle-based (AuNP-based) graphite furnace atomic absorption spectrometry (GFAAS) amplification and magnetic separation method for the detection of mercuric ions (Hg²⁺). The assay relies on (i) a sandwich-type structure containing two thymine-thymine (T-T) mismatches for selectively recognizing Hg²⁺ ions; (ii) magnetic beads for homogeneous separation; and (iii) AuNP-based GFAAS amplification detection. The limit of detection (LOD) of this assay is 0.45 nM (0.09 μg L⁻¹)--one order of magnitude lower than the United States Environmental Protection Agency (US EPA) limit for Hg²⁺ in drinking water. Furthermore, because a shorter hybridization step and a simpler AuNP-based GFAAS amplification detection were employed, a faster analytical run time allowing us to analyze a batch of 24 samples within 0.5 h. We demonstrated the feasibility of the developed approach for the determination of Hg²⁺ in urine and aqueous environmental samples.