SENSITIZED DETERMINATION OF MERCURY BY COLD VAPOR GENERATION FROM MICELLAR MEDIA AND ATOMIC-ABSORPTION SPECTROMETRY

The effect of surfactant media on mercury cold vapour (CV) generation prior to determination of this analyte by atomic absorption spectromet ry (AAS) was evaluated for the first time. The surfactants studied inc luded the anionic agents sodium laurylsulphate (SDS) and sodium diocty lsulphosuccinate (SDSS); the cationic compounds hexadecyltrimethylammo nium bromide (CTAB) and tetradecyltrimethylammonium bromide (TTAB); an d the non-ionic Triton X-100 at concentrations ranging from 0 to 2 or 10 times the characteristic micellar concentration (CMC). The Hg vapou r was generated from each medium in both continuous and flow injection (FI) modes using NaBH4 as reductant. The analytical performance of ea ch medium was compared to that of water and reaction mechanisms are pr oposed. Different mechanisms seem to be involved in the generation of Hg cold vapour from surfactant media in the FI and continuous modes. T he most promising results were obtained when the Hg vapour was generat ed in continuous mode from the sodium dioctylsulphosuccinate solution, which gave a signal 50% higher than that for conventional Hg cold vap our generation. This increase could be attributed to the accumulation of Hg2+ on the anionic micelle surface as a result of electrostatic at traction, providing a better location for reduction of the analyte by sodium borohydride. The use of surfactant media increased the sensitiv ity of Hg determination by CVAAS, decreased the noise level and gave f aster and better stabilization of the analytical signal.