Tannic acid capped gold nanoparticles with a mean diameter of 20nm were efficiently prepared by the green synthetic route. The size and morphology of gold nanoparticles were investigated by transmission electron microscopy and atomic force microscopy. The gold nanoparticles were effectively applied for the development of a sensing system that can detect and extract Hg2+ ions as well as Pefloxacine in a single step due to the strong interaction of gold nanoparticles with Hg2+ ions and pefloxacin. The sensing ability of gold nanoparticles was deliberated for the selective removal of Hg2+ ions and pefloxacin using UV visible absorption. The UV visible absorption of tannic acid capped gold nanoparticles was satisfied by different metal salts and drugs. The synthesized nanoparticles showed stability within a pH range of 3-12 and to heating at 100 ºC for 5 minutes. Quenching of the peak and precipitation is observed with various concentrations of brine solutions. Job’s plot analysis shows the binding stoichiometry to be a 1:1 ratio. This newly designed sensor offers a simple low-cost alternative tool for recognition and extraction of Hg2+ and pefloxacin.