CVAAS determination of naturally occurring levels of mercury in sediments after on-line preconcentration with a sol–gel sorbent doped with CYANEX-301

Abstract

A new on-line preconcentration method for total mercury determination in sediments by cold vapour atomic absorption spectrometry (CVAAS) was developed. The automated on-line preconcentration step was carried out using a micro-column packed with a sorbent prepared by the sol–gel technique. Tetraethoxysilane (TEOS) as the silica precursor and bis(2,4,4-trimethylpentyl)-dithiophosphinic acid (CYANEX 301) as the mercury extractant were used in the sol–gel sorbent preparation. Mercury was eluted quantitatively from the column using 2 mol L⁻¹ HCl and mixed on-line with NaBH₄ as the reducing agent. The effect of various instrumental parameters on the analytical performance was studied. The method detection limit (DL) traced back to the quantity of sample, based on three times the standard deviation of ten sample blank measurements, was 13.2 ng g⁻¹. The calibration curves were linear from 0.1 μg L⁻¹ to 2 μg L⁻¹ of Hg. The measurement precision, evaluated as the relative standard deviation obtained after analyzing ten replicates, was 0.83% and 1.04% at the 1 and 0.5 μg L⁻¹ level of Hg(II), respectively. The accuracy of the method was examined by the analysis of certified reference materials and confirmed by ICP-MS determinations. A sample throughput of 30 measurements per hour was possible.