On-line preconcentration of mercury by sorption on an anion-exchange resin loaded with 1,5-bis[(2-pyridpl)-3-sulphophenyl methylene] thiocarbonohydrazide and determination by cold-vapour inductively coupled plasma atomic emission

1,5-Bis[(2-pyridyl)-3-sulphophenyl methylene] thiocarbonohydrazide (PSTH) immobilized on an anion-exchange resin (Dowex) has been used for the on-line preconcentration of mercury from biological samples and waters prior to its determination by inductively coupled plasma atomic emission spectroscopy. The metal was eluted from the column using a solution of 2 M HNO3 and mixed on-line with SnCl2. The optimum experimental conditions were evaluated for the continuous preconcentration of Hg, the direct generation of mercury vapour and the final determination of this element by ICP-AES. The enrichment, together with low blank levels of the optimized procedure, allow the simple determination of this toxic element at concentrations down to a few nanograms per milliliter. 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 sampling rate of 40 h(-1), investigated with a 9 ml sample volume. The precision of the method (evaluated as the relative standard deviation obtained after analyzing ten series of ten replicates) was +/- 3.6% at the 10 ng ml(-1) level of Hg(II) and +/- 1.3% at the 100 ng ml(-1) level. The accuracy of the method was examined by the analysis of certified reference materials. (C) 1998 Elsevier Science B.V. All rights reserved.