Ultra sensitive quantification of Hg$^{2+}$  sorption by functionalized nanoparticles using radioactive tracker spectroscopy

We present an ultra sensitive method to quantify the uptake of Hg by dithiocarbamate functionalized magnetic nanoparticles using radioactive tracker spectroscopy. We show a lower limit of detection of about 10 fg L-1, much lower than any other known techniques used to determine the uptake of Hg (about 104 more sensitive), without the need of digesting or processing the sorption agent. Such high sensitivity enables the characterization of Functionalized Nanoparticles as Hg sorbents in natural waters, where the low Hg concentration is very difficult to detect using current analytical methods such as absorption/fluorometry methods (namely Cold Vapour Atomic Absorption/fluorescence spectroscopy). Radioactive trackers also give the ability to track the sorbed element, allowing the reconstruction of the path made by the sorbed element during the uptake process, unveiling further information about the impact of toxic metals in the environment and living beings.