ANALYTIcA CHIMICA zyxwvutsrqpo ACTA Analytica Chimica Acta 296 (1994) 181-193 Palladium as a chemical modifier for the determination of mercury in marine sediment slurries by electrothermal atomization atomic absorption spectrometry P. Bermejo-Barrera *, J. Moreda-Piiieiro, A. Moreda-Pifieiro, A. Bermejo-Barrera zyxwvutsrqpo Departmentof Analy tical Chemistry, Nutrition and Bmmutology,Faculty of Chemistry,University of Santiagode Compostela, 15706 Santiagode Compostela, Spain Received 17 January 1994; revised manuscript received 25 April 1994 Ahstraet A method for the determination of mercury in marine sediment slurries by electrothermal atomization atomic absorption spectrometry was optimized. It was found that a particle size < 20 pm is sufficient to achieve total atomization of the mercury content in the solid particles of the slurry. This particle size was achieved with simple mechanical grinding, using zirconia beads. The use of different thickening agents, viz., Triton X-100, Viscalex HV30 and glycerol, during the slurry preparation was studied. In addition, an acid predigestion was applied to verify the efficiency of the slurry sampling. The use of palladium at a concentration of 15 mg I-’ was found satisfactory for stabilizing mercury at 2CKK. Three charring steps, two involving an oxidative process, were studied. The optimum atomization temperature was 1450°C. A limit of detection of 70 pg kg-’ was achieved. The standard additions method was used for the determination of mercury in marine sediment samples from the Galician coast, the levels being between 2.2 and 3.2 mg kg-‘. IEeywora!s: Atomic absorption spectrometry; Marine sediments; Mercury; Slurry sampling 1. Introduction Water quality can be evaluated by studying trace element concentrations in waters, suspen- ded and bed sediments and biota samples. Usu- ally, most water quality investigations have at- tempted to assess elements in aquatic systems by analysing water samples. Nevertheless, in most * Corresponding author. aquatic systems, the concentrations of pollutant elements in bed sediments are far greater than the concentrations of trace elements in water [1,2]. The strong association of trace elements, such a Pb, Zn, Cd, As and Hg, with suspended and bottom sediments means that the distribu- tion, transport and availability of these con- stituents cannot be evaluated solely through the sampling and analysis of the dissolved phase. On the other hand, the study of a sediment column gives information about the element concentra- tion changes over time and thus the area baseline ooO3-2670/94/$07.00 0 1994 Elsevier Science B.V. All rights reserved SSDZOOO3-2670(94)00204-Y