4.6 Article Proceedings Paper

Determination of mercury in gasoline by cold vapor atomic absorption spectrometry with direct reduction in microemulsion media

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PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.sab.2005.02.026

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mercury determination; gasoline; microemulsion; cold vapor atomic absorption spectrometry

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The determination of Hg in gasoline by cold vapor atomic absorption spectrometry, after direct aqueous NaBH4 reduction in a three-component (microemulsion) medium, was investigated. Microemulsions were prepared by mixing gasoline with propan-1-ol and 50% v/v HNO3 at a 20:15:1 volume ratio. A long-term homogeneous system was immediately formed this way. After reduction, the Hg vapor generated in a reaction flask was transported to an intermediate K2Cr2O7/H2SO4 trap solution in order to avoid poisoning of the Au-Pt trap by the gasoline vapors. A second reduction step was then conducted and the generated Hg vapor transported to the Au-Pt trap, followed by thermal release of Hg-0 and atomic absorption measurement. Purified N-2 was used as purge and transport gas. After multivariate optimization by central composite design calibration graphs showed coefficients of correlation of 0.9999 and a characteristic mass of 2 ng was obtained. Typical coefficients of variation of 5% and 6% were found for ten consecutive measurements at concentration levels of 1 and 8 mu g L-1 of Hg2+, respectively. The limit of detection was 0.10 mu g L-1 (0.14 mu g kg(-1)) in the original sample. A total measurement cycle took 11 min, permitting duplicate analysis of 3 samples per hour. The results obtained with the proposed procedure in the analysis of commercial gasoline samples were in agreement with those obtained by a comparative procedure. Gasoline samples of the Rio de Janeiro city have shown Hg concentrations below 0.27 mu g L-1. (c) 2005 Elsevier B.V All rights reserved.

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