Determination of arsenic, lead, selenium and tin in sediments by slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry using Ru as permanent modifier and NaCl as a carrier

A procedure for the determination of As, Pb, Se and Sn in sediment slurries by electrothermal vaporization inductively coupled plasma mass spectrometry is proposed. The slurry, I mg ml(-1), is prepared by mixing the sample ground to a particle size less than or equal to 50 mum with 5% v/v nitric and 1% v/v hydrofluoric acids in an ultrasonic bath. The slurry was homogenized with a constant flow of argon in the autosampler cup, just before transferring an aliquot to the graphite furnace. The tube was treated with Ru as a permanent modifier, and an optimized mass of I mug of NaCl was added as a physical carrier. The pyrolysis temperature was optimized through pyrolysis curves, and a compromised temperature of 800 degreesC was used; the vaporization temperature was 2300 degreesC. The effect of different acid concentrations in the slurry on the analyte signal intensities was also evaluated. The accuracy of the method was assured by the analysis of certified reference sediments MESS-2, PACS-2 and HISS-1 from the National Research Council Canada, SRM 2704 and SRM 1646a from the National Institute of Standards and Technology and RS-4 from a round robin test, using external calibration with aqueous standards prepared in the same medium as the slurries. The obtained concentrations were in agreement with the certified values according to the Student's t-test for a confidence level of 95%. The detection limits in the samples were: 0.17 mug g(-1) for As; 0.3 mug g(-1) for Pb; 0.05 mug g(-1) for Se and 0.28 mug g(-1) for Sri. The precision found for the different sediment samples, expressed as R.S.D. was 1-8% for As, 29% for Pb, 6-12% for Se and 3-8% for Sn (n = 5). (C) 2002 Elsevier Science B.V. All rights reserved.