A rapid acid digestion method with ICP-MS detection for the determination of selenium in dry sediments Original Research Article

Selenium (Se) is an essential element to organisms with the following peculiarity: at low concentrations anomalies are observed due to the specific biochemical changes, and at higher concentrations it becomes a toxic element. The interval of essential concentrations is in general very narrow. This dual Se behaviour has stimulated the development of numerous analytical methods for its determination in environmental and biological samples. The baseline concentration of Se in sediments is low (0.05 μg g−1), meaning that very sensitive analytical methods with low detection limits are required. We developed a simple and rapid method based on a pre-treatment/digestion of dry sediment samples with aqua-regia and HCl and quantification by ICP-MS using 82Se. Obtained and certified Se concentrations for international certified reference materials MESS-1, MESS-2, BCSS-1 and 1646a, showed no statistically differences (α = 0.05) between obtained and certified values. Low detection limits (approximately 0.03 μg g−1), good repeatability (<1.5%) and recoveries (98–103%) made this method a useful tool for rapid selenium analyses in dry sediments. This method was applied to 50 surface sediments collected in the Tagus estuary giving a rapid image of the distribution of total selenium concentrations in the estuary.