engleski

Microwave-assisted determination and speciation of mercury in sediments

Sample preparation is a critical factor in the analysis of environmental samples. Microwave digestion could be a method of choice over conventional procedures due to shorter extraction times, higher extraction efficiency and easier control of digestion parameters. In this work the application of an open focused microwave system for mercury speciation in sediment and interstitial water were investigated. Quantitative leaching of total mercury is achieved by heating the sediment in concentrated nitric acid during 5 min at a power of 30 W, compared to 4-6 hours required with conventional heating. Samples for methylmercury determination were prepared by sediment extraction with diluted sulphuric acid in the open microwave field during 5 min at a power of 60 W. This treatment proved to be efficient enough to extract, but not to decompose methylmercury present in sediment. The extracted methylmercury was separated from inorganic mercury by distillation, and detected as inorganic mercury after decomposition by BrCl oxidation. Oxidation of methylmercury could be also significantly improved by microwave heating, as decomposition can be fulfilled in 3 min with 0.5 % BrCl, instead within several hours in 2.5 % BrCl solution. In addition, a standard procedure for total mercury determination in natural waters based on oxidation of organically complexed mercury by 0.5 % BrCl solution proved to be sometimes insufficient in the case of sediment porewaters. However, in such samples microwave-assisted BrCl oxidation fully liberates mercury from organic complexes during 3 min at a power of 30 W. Therefore, the application of microwave digestion can significantly improve determination of different mercury species in both solid sediment samples and in porewaters.

nije evidentirano

nije evidentirano