One-pot synthesis of a magnetic nanocomposite based on ultrasound-assisted co-precipitation for enrichment of Hg(II) prior to detection by a direct mercury analyzer

Ultrasound-assisted co-precipitation was applied to construct a magnetic nanocomposite following a 'one-pot' synthetic strategy for Hg(II) enrichment. The presence of a noble metal such as Ag(I), Au(III), Pd(II) in the synthesis medium proved to be essential in order to attain an efficient co-precipitation of Hg with the magnetic nanoparticles. Following this preconcentration procedure, thermal desorption and a further preconcentration was carried out by amalgamation onto a gold coil placed inside a direct mercury analyzer working under the principle of atomic absorption. The magnetic nanocomposite was characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy coupled to energy dispersive X-ray spectrometry (HR-TEM-EDS) and total reflection X-ray fluorescence (TXRF). Magnetic nanoparticles with a size in the range of ca. 7-11 nm were obtained. After full optimization of variables influencing the preconcentration and detection of Hg, analytical characteristics were obtained. A detection limit as low as 3.2 ng/L Hg was obtained when 50 mu L of the magnetic phase were introduced in the mercury analyzer. The repeatability and reproducibility expressed as relative standard deviation (RSD) were 7% and 10%, respectively. Several certified reference materials, synthetic and unknown water samples were analyzed showing Hg recoveries in the range of 88-115%.