Use of flow injection cold vapour generation and preconcentration on silica functionalized with methylthiosalicylate for the determination of mercury in biological samples and sea-water by inductively coupled plasma atomic emission spectrometry

Abstract

A novel and expeditious approach to the direct determination of mercury in sea-water and biological samples based on a separation–preconcentration system coupled on-line to a flow injection (FI) manifold is described. The method employs on-line preconcentration of mercury on a 3 cm×3 mm column packed with silica gel functionalized with methylthiosalicylate (TS-gel) and placed in the injection valve of the FI manifold. Synthesis of the resin is simpler and faster than that of other resins described previously, where many steps are required. In this system the metal was eluted from the column with thiourea and mixed on-line with NaBH₄; mercury vapour was generated directly and separated via a gas–liquid separator. Various parameters and chemical variables affecting the preconcentration of Hg^II, the direct generation of mercury vapour and the final determination by ICP-AES were evaluated. The calibration graph was linear over the range 5–1000 ng ml^–1 Hg^II, with a relative standard deviation at the 10 ng ml^–1 level of 2.1%. The accuracy of the method was evaluated by the analysis of certified reference materials. The results showed good agreement with the certified values.