Sensitized determination of mercury by cold vapour generation from micellar media and atomic absorption spectrometry

Abstract

The effect of surfactant media on mercury cold vapour (CV) generation prior to determination of this analyte by atomic absorption spectrometry (AAS) was evaluated for the first time. The surfactants studied included the anionic agents sodium laurylsulphate (SDS) and sodium dioctylsulphosuccinate (SDSS); the cationic compounds hexadecyltrimethylammonium bromide (CTAB) and tetradecyltrimethylammonium bromide (TTAB); and the non-ionic Triton X-100 at concentrations ranging from 0 to 2 or 10 times the characteristic micellar concentration (CMC). The Hg vapour was generated from each medium in both continuous and flow injection (FI) modes using NaBH 4 as reductant. The analytical performance of each medium was compared to that of water and reaction mechanisms are proposed. Different mechanisms seem to be involved in the generation of Hg cold vapour from surfactant media in the FI and continuous modes. The most promising results were obtained when the Hg vapour was generated in continuous mode from the sodium dioctylsulphosuccinate solution, which gave a signal 50% higher than that for conventional Hg cold vapour generation. This increase could be attributed to the accumulation of Hg 2+ on the anionic micelle surface as a result of electrostatic attraction, providing a better location for reduction of the analyte by sodium borohydride. The use of surfactant media increased the sensitivity of Hg determination by CVAAS, decreased the noise level and gave faster and better stabilization of the analytical signal.