Determination of Hg in water associate to crude oil production by electrothermal vaporization inductively coupled plasma mass spectrometry

Mercury is a toxic element that can be found in different chemical forms in the environment. It can be present in crude oil and contaminate the water employed in the oil extraction and production. Sample treatment required for most spectrometric techniques can lead to errors in the Hg determination, mainly by volatilization. Vapor generation is the most recommended technique for sample introduction, but is too time consuming. In this work, electrothermal vaporization was the chosen alternative for sample introduction in inductively coupled plasma mass spectrometry to allow the accurate determination of Hg in production water. Samples were analyzed by analyte addition in one sample with low Hg content. In order to avoid Hg loss, low temperatures were employed in the ETV program, pyrolysis at 200 degrees C and vaporization at 1000 degrees C, and gold was used as modifier. Limit of detection of 0.12 mu g L-1 and limit of quantification of 0.41 mu g L-1 were obtained. Accuracy was checked using recovery test, by adding an urine certified sample to a production water sample and an average recovery of 106% was obtained. Among the 10 samples analyzed, one presented Hg concentration over the limit for effluents, established by Brazilian legislation. The proposed method presented better accuracy when compared to the analysis by ICP-MS with direct introduction by means of a nebulizer specific for saline samples. (C) 2012 Elsevier B.V. All rights reserved.