Solid sampling electrothermal vaporization inductively coupled plasma massspectrometry for the direct determination of Hg in sludge samples

The present paper reports on the use of solid sampling electrothermal vapor ization-inductively coupled plasma mass spectrometry (ETV-ICP-MS) for the d irect determination of Hg in sludge samples. For 'real-life' samples, the p retreatment was limited to drying, sieving and finally homogenization by me ans of shaking. One milligram amounts of the samples of interest were inser ted into a graphite furnace coupled to a quadrupole-based ICP-mass spectrom eter for subsequent analysis. The temperature programme of the graphite fur nace was selected such that Hg was vaporized and transported into the plasm a at a relatively low temperature (approximate to 700 degrees C). Under the se conditions, co-volatilization of considerable amounts of the matrix, lea ding to signal suppression and hence, curvature of the mass response curve, could be avoided. Quantification was accomplished by means of external cal ibration, using a (solid) certified reference material, with a matrix compo sition comparable to that of the samples. The accuracy attainable was evalu ated by means of (i) analysis of a sludge certified reference material and (ii) comparison of the ETV-ICP-MS result for a 'real-life' sample with the aqua regia extractable Hg content, as determined by pneumatic nebulization ICP-MS after sample processing according to the German standard DIN 38414-S 7. Although in all cases, the precision was observed to be Limited by the i nhomogeneous distribution of the analyte element over the matrix, the ETV-I CP-MS result obtained for the sludge reference material showed an excellent agreement with the certified value, while for the 'real-life' sample, the average ETV-ICP-MS result agreed within 10% with the aqua regia extractable content. The approach developed was finally used for the analysis of sludg es sampled at different locations in Limburg (Flanders, Belgium). For all b ut one sample, the Hg content was seen to be below the maximum allowable co ntent, as specified in Flanders. (C) 1999 Elsevier Science B.V. All rights reserved.