Abstract.A flow injection-cold vapour atomic absorption spectrometric (CVAAS) method was developed for the determination of mercury at trace level in estuarine sediments using sodium tetrahydroborate (III) as reductant. The mercury was solubilized with nitric acid in closed vessels and microwave oven heating. Instrumental and operational conditions (volume and concentration of reagents, reaction time, etc.) were optimized. The effect of several ions on the analytical signal was also studied; no interferences were recorded excepting for copper and nickel which caused a serious depressing effect. The detection limit obtained was 0.01 µg g -1 . The validation of the method was performed analyzing a certified reference sediment, BCR CRM 277 Estuarine Sediment. Good recovery (c.a. 98%) and precision (< 3%, RSD) were achieved. The proposed method was successfully applied to the determination of mercury in sediment samples from Ares-Betanzos Estuary (Galicia, NW Spain).
A simple and fast metal extraction method that combines closed vessels and microwave heating for the simultaneous extraction often selected heavy metals (As, Cd, Co, Cr, Hg, Mn, Ni, Pb, Zn) from marine sediments is proposed. Digestion conditions, i.e. power and times microwave irradiation, reagent extractant, sample amount, were optimized to recover the potentially available metallic fraction not bound in silicates. A nitric acid and two step microwave program was established. 140 MARTINEZ-GARCIA ET AL. The resulting solutions were analyzed by flame (FAAS), hydride generation (HG-AAS) and cold vapour (CV-AAS) atomic absorption spectrometry. Quantifications were made using direct calibration with aqueous standards. The recoveries of the spiked samples investigated ranged from 89 to 113%. The results obtained from analyzing the BCR certified reference sediment CRM 277 Estuarine Sediment were in good agreement with the certified values (93-105%), except for low values for chromium (79%). The relative standard deviations for the determination of metals were less than 4 %. Finally, the technique designed herein was applied to sediment samples from La Coruna estuary, NW Spain.
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