Microwave preparation of natural samples to the determination of mercury and other toxic elements by atomic absorption spectrometry

Methods have been developed for the preparation of samples containing organic matrices (natural high-color waters, soils, bottom sediments, aquatic organism tissue) to the determination of mercury and other toxic elements (As, Cd, Pb, Se) by different procedures of microwave digestion under elevated pressure (closed systems, vessels with partial removal of the gas phase). It is found that, under optimal oxidative and temperature-time conditions, the partial removal of the gas phase does not lead to losses of volatile elements if sample portions under 2 g are used. The duration of preparation of a series of samples does not exceed 40 min. The detection limits for mercury in the cold vapor atomic absorption spectrometry and for Cd, Pb, As, and Se by electrothermal atomic absorption spectrometry are 5 and 0.13, 6, 13, and 13 μg/kg, respectively. The accuracy of determination is confirmed by the results of analysis of certified reference materials of water and plant materials and also by the standard addition method. The selected conditions of preparation of sludge samples have ensured the determination of mercury by the cold vapor atomic absorption spectrometry in drinking, natural, and sewage waters with a detection limit of 0.07 μg/L.