Development of an ultrasound-assisted extraction method for biomonitoring of vanadium and nickel in the coastal environment under the influence of the Prestige fuel spill (North east Atlantic Ocean)

As a consequence of the Prestige shipwreck occurred in the Northeast Atlantic Ocean in November 2002, the need for establishing the environmental impact caused by metals has been of primary concern. Among the different metals contained in the fuel spill, V and Ni are particularly of interest since they appear at relatively high concentration in the original fuel. Biomonitoring of V and Ni using wild mussels (Mytilus edulis) collected along the Galician Coast (NW Iberian Peninsula) has been performed. Ultrasound-assisted extraction of V and Ni from dried mussel tissues using probe sonication allowed a fast solid-liquid extraction thus facilitating sample preparation from large sample batches used for biomonitoring. V and Ni were determined in shellfish caught in the Galician littoral and tar balls from the Prestige spill by electrothermal-atomic absorption spectrometry and inductively coupled plasma-optical emission spectrometry, respectively. A Plackett-Burman saturated design was applied for screening optimization of variables influencing the ultrasound-assisted extraction of V and Ni from shellfish. Efficient extraction of both metals was obtained from slurries prepared in 2 mL capacity sample vials (10 mg sample with a particle size less than 100 μm) using a 3% (v/v) HNO₃ diluent and subjected to probe sonication (3 min; 30% vibrational amplitude of the probe). The method was successfully validated by means of three certified reference materials: NRCC-TORT-2 Lobster hepatopancreas, NIST-SRM 1566b Oyster tissue and NIST-SRM 2977 Mussel tissue. The detection limit (LOD) of V and Ni in the marine biological tissues, calculated according to the 3σ criterion, were 0.24 μg g⁻¹ and 0.15 μg g⁻¹ for V and Ni, respectively. V and Ni concentrations in M. edulis were in the range 1.7-4.8 and 0.8-2.8 μg g⁻¹, respectively. Whilst no significant variations in Ni contents were observed in regard to reference values, an important increase in V concentration is observed at some sampling points, thereby indicating bioaccumulation.