ONLINE PRECONCENTRATION OF MERCURY BY SORPTION ON AN ANION-EXCHANGE RESIN LOADED WITH 1,5-BIS[(2-PYRIDPL)-3-SULFOPHENYL METHYLENE] THIOCARBONOHYDRAZIDE AND DETERMINATION BY COLD-VAPOR INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION

1,5-Bis[(2-pyridyl)-3-sulphophenyl methylene] thiocarbonohydrazide (PS TH) immobilized on an anion-exchange resin (Dowex) has been used for t he on-line preconcentration of mercury from biological samples and wat ers prior to its determination by inductively coupled plasma atomic em ission spectroscopy. The metal was eluted from the column using a solu tion of 2 M HNO3 and mixed on-line with SnCl2. The optimum experimenta l conditions were evaluated for the continuous preconcentration of Hg, the direct generation of mercury vapour and the final determination o f this element by ICP-AES. The enrichment, together with low blank lev els of the optimized procedure, allow the simple determination of this toxic element at concentrations down to a few nanograms per millilite r. The proposed method has a linear calibration range 5-1000 ng ml(-1) of mercury, with a detection limit of 4 ng ml(-1) (S/N = 3) and a sam pling rate of 40 h(-1), investigated with a 9 ml sample volume. The pr ecision of the method (evaluated as the relative standard deviation ob tained after analyzing ten series of ten replicates) was +/- 3.6% at t he 10 ng ml(-1) level of Hg(II) and +/- 1.3% at the 100 ng ml(-1) leve l. The accuracy of the method was examined by the analysis of certifie d reference materials. (C) 1998 Elsevier Science B.V. All rights reser ved.