Authors: M. Costas, C. Fernández, Isela Lavilla, Carlos Bendicho
Journal: Journal of Spectroscopy and Dynamics, 2: 1-7, 01/2012
In this work, the detection of arsenic in river sediments by flow injection-hydride generation atomic absorption spectrometry (FI-HG-AAS) after a sample pre-treatment method based on ultrasound-assisted extraction (UAE) is described. The influence of ultrasound on total arsenic measurements was evaluated. For this, a certified reference material (CRM) BCR-320 and a field sample of river sediment were used. Parameters influencing extraction such as acid extractant concentration, sample mass, sonication time and sonication amplitude were carefully optimized. In addition, the effect of particle size and drying method were also studied. Optimal conditions were 25 % v/v HCl as extractant, 20-30 mg of sample mass, 3 min of sonication time, 50 % of sonication amplitude, particle size < 50 µm and freeze-drying as drying method. Both samples contained a mixture of As(III) and As(V). Ultrasonic pre-treatment showed the ability to extract efficiently arsenic from the samples and to oxidize As(III) into As(V). This finding is remarkable, since the analytical response depends on the As oxidation state in the hydride generation technique. Therefore, conversion of As species extracted into an only valence state facilitates calibration and allows total As quantification without bias. Practical demonstration of the dual effect of ultrasound by activating extraction and oxidation processes is provided.