Simultaneous determination of As, Hg, Se and Sb by hydride generation-microwave induced plasma atomic emission spectrometry after preconcentration in a cryogenic trap

In this paper a system is presented which combines hydride generation with a preconcentration step in a cryogenic trap and detection using MIP-AES. The MIP has been operating at atmospheric pressure with a forward power of 30-150 W, using a TM₀₁₀ cavity (Beenakker resonator), equipped with a tangential flow torch design. The plasma emission was observed end-on by the means of a CCD camera coupled to a 0.5 m Czerny-Turner design monochromator. Metal hydrides were generated batchwise in aqueous medium, preconcentrated in a liquid nitrogen cryogenic trap and then evaporated by electrical heating into the plasma discharge. The optimum working conditions have been found at the 197±7 nm window working with a forward power of 130 W, a plasma gas flow rate of 270 ml min^–1 of helium, a carrier gas flow rate of 134 ml min^–1 of helium, a NaBH₄ concentration of 2% and a HNO₃ concentration of 0.66 M. Under these conditions detection limits of 2.0, 13, 2.2 and 3.3 µg L^–1 for As, Hg, Se and Sb were achieved. The method was applied to the detemination of these analytes in spiked wastewater samples with recoveries of 95% or higher for all four analytes.