Alginate-based magnetic nanosorbent immobilized with aptamer for selective and high adsorption of Hg in water samples.

Alginate-coated magnetic nanocluster (MNC) immobilized with Hg-specific aptamer was synthesized to obtain the nanosorbent with high adsorption capacity and high selectivity for trace analysis of inorganic mercury (Hg) in water samples. Magnetite nanoparticle was first synthesized by a co-precipitation of iron precursors in the presence of alginate to obtain alginate-coated MNC, followed by immobilization with avidin. Hg-Specific DNA aptamer labeled with biotin was then conjugated on the MNC surface via specific avidin-biotin interaction to form aptamer-immobilized MNC. Coating the MNC with alginate can improve its water dispersibility and also increase its adsorption capacity toward Hg (350 mg/g). It exhibited high selectivity through thymine-Hg-thymine (T-Hg-T) interaction with high tolerance to other foreign ions. This nanosorbent showed linearity over the Hg concentration range of 0.2-10 μg/L with a correlation coefficient of 0.9977, limit of detection of 0.46 μg/L, and enrichment factor of 13. Moreover, it also showed a potential for detection of Hg in drinking and tap water samples with satisfactory recoveries.