Microwave-assisted determination of total mercury and methylmercury in sediment and porewater

Abstract

Microwave-assisted extraction methods for sample preparation have been evaluated in various environmental applications, as are total digestion for element analysis or extraction of selected organic compounds. This technique has been confirmed as a method of choice over conventional procedures for digestion of mineral and biological samples for total Hg determination [1,2,3], due to a shorter extraction time, a higher extraction efficiency and easier control of digestion parameters. Both closed and open microwave systems are used for the digestion of samples for the total Hg analyses. However, determination of the total Hg in environmental samples is not sufficient, as Hg is partly in the form of methylmercury (MeHg), which is considerably more toxic than the inorganic Hg. A particularly difficult task is the determination of MeHg in sediment, where it makes a very low percentage of the total Hg (< 2 %). Only recently, an open low-power focused microwave system has been verified as an appropriate tool for preparation of solid samples for organometallic speciation analysis [4]. It has been used for developing of the isolation procedure of MeHg in sediment based on the microwave-assisted leaching of MeHg with dilute acids [5].In this work, the application of open microwave system for the total Hg and MeHg determination in sediment and porewater is described. Microwave-assisted leaching of the total Hg and MeHg from sediment with an acid extractant, provided a rapid way of separation of these species from the matrix prior to detection by CV AFS (cold vapour atomic fluorescence spectroscopy). Microwave-assisted BrCl oxidation was proved to be more effective for the decomposition of MeHg and stable organomercury complexes in solution (distillate or porewater), as compared with BrCl oxidation at room temperature. Material and methods ReagentsAcids used were of analytical quality (HNO 3 , HCl) or suprapur grade (HCl, Merck). Hg standard was prepared from stock standard solution (1 g/L, Merck). A standard solution was prepared weekly in 10 % HNO 3 and 0.01 % of K 2 Cr 2 O 7, whereas reference standard solutions were prepared daily in 1 % HNO 3 . A reductant solution (5 % SnCl 2 in 10 % HCl) was prepared by dissolving SnCl 2 in concentrated HCl and diluting with water. The certified reference sediments used for verification were PACS-1 (National Research Council of Canada -NRCC) and CRM 580 (Community Bureau of Reference of the European Communities -BCR). 871Microwave-assisted determination of total mercury and methylmercury in sediment and porewater

Ultrasound-assisted extraction of Ca, K and Mg from in vitro citrus culture

“…As nitric acid is generally used for sample extraction/decomposition [17][18][19] and because it provides a good medium for working with FAAS technique, [20][21][22] it was chosen as the extracting medium for this purpose.…”